Volume 2 Flashcards
1
Q
The term that best describes the water found within cells is
A
intracellular water.
2
Q
An example of calculated supplemental data is
A
the anion gap.
3
Q
A trend in high or low anion gaps indicates that
A
there may be a consistent error in at least one of the analytes.
4
Q
The ultimate regulators of sodium levels in the body are the
A
kidneys through reabsorption and excretion.
5
Q
Hemolyzed samples for potassium analysis should be avoided because
A
intracellular potassium will be released, affecting results.
6
Q
In the disease cystic fibrosis, the concentration of chloride ions in sweat is
A
elevated due to a genetic defect.
7
Q
If you discover that a sample for bicarbonate analysis has been left open in a test tube rack, the result could be
A
falsely decreased due to CO2 escaping into the air.
8
Q
Because the lungs and kidneys regulate acid-base balance, a patient with disorders affecting these organs will be followed using
A
blood gas analysis.
9
Q
What happens during internal respiration when the partial pressure of oxygen is 90 mm Hg and carbon dioxide is about 40 mm Hg?
A
Oxygen moves into the cell and carbon dioxide moves out of the cell.
10
Q
Blood gas samples should be collected only by
A
providers or specially trained personnel.
11
Q
What do you do if you receive a blood gas sample with an air bubble in it?
A
Annotate the final report with the condition the sample was in when it arrived in the laboratory.
12
Q
The importance of pH in the blood is critical because
A
a pH outside of 6.8 to 7.8 is incompatible with life.
13
Q
Which one of the following substances is a buffer found in large amounts and has its concentrations within the body controlled by the lungs and the kidneys?
A
Bicarbonate.
14
Q
The lungs help maintain body pH by converting carbonic acid into carbon dioxide and water, which
A
are then expelled during exhalation.
15
Q
What are the body processes that water and electrolytes work hand-in-hand to accomplish?
A
Water balance, osmolality, electrolyte balance, pH balance, and blood gas exchange.
16
Q
What are intracellular and extracellular water?
A
Intracellular water is found within the cells. Extracellular water is water found outside of the cells.
17
Q
What is the concept of water balance?
A
Water balance is keeping the intracellular and extracellular compartments of water at a constant volume. This is done by ensuring that the rate of water loss is equal to the rate of water intake.
18
Q
List the factors that regulate water balance?
A
It’s regulated by the body’s thirst mechanism, anti-diuretic hormone produced by the posterior pituitary gland, and excretion or reabsorption of water by the kidneys.
19
Q
What are the six causes of fluid imbalances?
A
Vomiting. Excessive urination. Sweating. Diarrhea. Bleeding. Exudation.
20
Q
In chemistry, the term electrolytes refer to what analytes?
A
Sodium, potassium, chloride, and bicarbonate.
21
Q
- (204) Respiratory acidosis means the blood pH is
A
decreased due to a respiratory problem.
22
Q
- (204) A tourniquet, used during venous blood collection, affects pH readings by causing
A
the blood to stagnate, resulting in a decrease of venous pO2.
23
Q
- (205) Decreased levels of calcium are often associated with tetany,
A
a hyperexcitability of nerves and muscles.
24
Q
- (205) Increased calcium levels are known as
A
hypercalcemia.
25
19. (205) Hemolyzed samples should not be used for phosphate analysis because
red blood cells contain high concentrations of organic phosphate esters.
26
20. (206) The main dietary sources of magnesium are
meat and green vegetables.
27
21. (206) One of the more serious complications of magnesium deficiency is the effect on the
cardiovascular system.
28
22. (206) Analysis of which one of the following analytes is often requested to track patients with manic-depressive illnesses?
Lithium.
29
23. (207) All test methods for serum iron measure
iron carried by transferrin.
30
24. (207) Iron levels in the body are regulated by
absorption.
31
25. (207) Total iron binding capacity (TIBC) measures
maximum amount of iron-carrying capacity of transferrin.
32
26. (207) Iron overload may be accelerated by
chronic alcoholism.
33
27. (208) Among some of the liver’s functions is the ability to
convert glucose to glycogen and glycogen back to glucose, as needed.
34
28. (208) The liver is the primary storage site for
glycogen.
35
29. (208) Hepatitis A virus is primarily transmitted through
the fecal oral route.
36
30. (208) Due to the amount of time it takes for antibodies to reach detectable levels and prior to the use of nucleic acid amplification testing (NAT), which type of hepatitis could not be eliminated completely by blood donor screening?
Hepatitis C virus.
37
31. (208) What hepatitis virus occurs as a simultaneous infection with the Hepatitis B (coinfection) or as a superimposed infection in someone with chronic Hepatitis B (superinfection)?
Hepatitis D.
38
32. (209) Bilirubin that has become joined with glucuronic acid is called
conjugated bilirubin.
39
33. (209) When jaundice, a condition characterized by the deposit of a yellowish pigment in the skin and eyes, can be detected visually, the bilirubin level is
well above normal.
40
34. (209) In newborns, bilirubin levels can increase for the first few days of life before returning to normal because
the transferase enzyme system is not fully developed.
41
35. (209) Bilirubin levels increase due to the impairment or obstruction of the excretion of bile into the intestines, because bilirubin builds up in the hepatocytes, and is
regurgitated into the blood.
42
36. (209) Conditions such as hepatitis, which damage or destroy liver cells, are known as
intrahepatic disorders.
43
37. (209) Posthepatic disorders differ from intrahepatic disorders in that posthepatic disorders
can be corrected by surgical methods.
44
38. (209) Samples for bilirubin analysis should be protected from light because
both conjugated and unconjugated bilirubin are light sensitive.
45
39. (210) Carbohydrate classes, such as monosaccharides, disaccharides, and polysaccharides, are determined based on
the number of sugars a carbohydrate can be broken down into during hydrolysis
46
40. (210) When excess carbohydrates are eaten, the body will change some of the excess into
fats and store them in that form.
47
41. (210) The breakdown of glycogen into glucose is called
glycogenolysis.
48
42. (211) The chief source of energy and the only monosaccharide found in significant amounts in the body fluids of living organisms is
glucose.
49
43. (211) When epinephrine is released due to physical or emotional stress, it causes
increased glucose levels for energy.
50
44. (211) The cause of Type 2 diabetes is
unknown.
51
45. (211) If an unconscious patient’s glucose result has been verified and it’s 35 mg/dl,
notify the attending physician at once, because the patient is hypoglycemic.
52
46. (211) When diagnosing diabetes mellitus, once the patient has met all required criteria, what other evaluations must be performed?
Hypertension and cardiovascular assessment.
53
47. (211) Which one of the following glucose tests requires patient preparation for 3 days prior to the testing date?
Oral glucose tolerance.
54
48. (211) Cerebrospinal fluid (CSF) glucose levels in bacterial meningitis patients are usually
lowered because glucose is utilized by the bacteri
55
49. (211) Serum for glucose testing should not be allowed to sit on the red blood cells for extended periods of time because
glycolysis can decrease the glucose level.
56
50. (211) One advantage of the hexokinase method over the glucose oxidase method, for glucose analysis, is
fewer substances will interfere with the hexokinase method.
57
51. (212) The active site of an enzyme is where the substrate bonds are strained, ruptured, and the
substrate is converted into a new substance.
58
52. (212) Substances that decrease enzyme activity, and are either competitive or non-competitive, are called
inhibitors.
59
53. (212) The point where the concentration of enzyme no longer effects the rate of the reaction is known as the
zero order reaction.
60
54. (212) Enzyme activators are usually
cations.
61
55. (213) Amylase is secreted by the
salivary and pancreatic glands.
62
56. (213) What source of amylase is the primary source of amylase responsible for carbohydrate break down?
Pancreatic.
63
57. (213) All of the following are starch-based methods used to measure amylase activity, except
flame photometric.
64
58. (214) The enzyme that splits off the phosphate group from organic phosphate esters in an alkaline solution is
alkaline phosphatase.
65
59. (214) Elevated amounts of alkaline phosphatase is normal in children because
of normal bone growth.
66
60. (215) Because alanine aminotransferase is found in moderately high concentrations in the liver and has low concentrations in skeletal and cardiac muscle, it is primarily used to
diagnose intracellular hepatic diseases.
67
61. (215) Alanine aminotransferase (ALT) will increase, even before the patient shows any clinical signs, in cases of
viral hepatitis or other liver diseases, which cause hepatic necrosis.
68
62. (215) After a myocardial infarction (MI), aspartate aminotransferase (AST) levels
increase and ALT levels will remain near normal.
69
63. (215) You have just run a panel and the alanine aminotransferase (ALT) and aspartate aminotransferase (AST) are elevated beyond the linear range of your analyzer. Although you can dilute the sample with saline, the preferred dilutant is
albumin solution.
70
64. (216) The function of gamma glutamyltransferase (GGT) is to
transport amino acids across cell membranes.
71
65. (216) Gamma glutamyltransferase (GGT) is considered a better indicator of obstructive jaundice than aspartate aminotransferase (AST), alanine aminotransferase (ALT), or alkaline phosphatase (ALP) because
its levels increase earlier and persist longer than the other enzymes.
72
66. (216) In addition to liver disease, the release of gamma glutamyltransferase (GGT) into the serum reflects
the toxic effects of alcohol or drugs on the liver cells.
73
67. (216) Normal reference ranges for gamma glutamyltransferase (GGT) run higher in males than in females because
there are high levels of GGT in the prostate.
74
68. (217) The peptide chains that make up lactic dehydrogenase (LD) isoenzymes are classified into two types—
M for skeletal muscle and H for heart muscle.
75
69. (217) Lactate dehydrogenase (LD) testing is often useful in making a delayed diagnosis of a myocardial infarction (MI) because
the increase in LD occurs later than the increase in creatine kinase (CK).
76
70. (217) In a normal lactate dehydrogenase (LD) isoenzyme pattern, the LD2 isoenzyme level is greater than the LD1 isoenzyme level. In a myocardial infarction (MI), the patient’s isoenzyme pattern will
be flipped, with LD1 greater than LD2.
77
71. (217) Lactate dehydrogenase (LD) isoenzymes analysis is performed by
electrophoresis.
78
72. (218) Creatine kinase (CK) is an enzyme that takes part in a reversible reaction—the direction of the reaction is dependent on the
pH of the reaction media.
79
73. (218) Although creatine kinase (CK) is found predominately in the heart, skeletal muscle, and brain, accurate differentiation for conditions involving CK is accomplished using
CK isoenzymes.
80
74. (218) Creatine kinase (CK) activity is most commonly used to assess patients with a myocardial infarction (MI) because it
begins to increase 3 to 6 hours after the MI.
81
75. (218) What creatine kinase (CK) isoenzyme makes up most of the normal circulating CK, but can be increased with exercise?
CK-MM (CK3).
82
76. (218) Most analyzer use the reverse reaction for creatine kinase (CK) analysis because
the reverse reaction is six times faster than the forward reaction.
83
77. (219) In addition to acid phosphatase (ACP), which of the following helps to investigate and monitor prostatic cancer?
Prostate-specific antigen (PSA).
84
78. (219) Forensic testing for acid phosphatase (ACP) is sometimes done during rape investigations because
seminal fluid contains high levels of ACP.
85
79. (219) Prostate-specific antigen (PSA) can be detected in all males; however,
levels are greatly increased in males with prostatic cancer.
86
80. (219) Prostate-specific antigen (PSA) is replacing acid phosphatase (ACP) as a screening tool for early detection of prostatic cancer due to
lack of sensitivity of ACP in early disease stages.
87
81. (220) Calcium is required for lipase activity, but at high concentrations will serve as a(n)
inhibitor.
88
82. (221) The best use of a myoglobin determinations is
to rule out a myocardial infarction.
89
83. (221) Interference with troponin cTnT studies can be caused by
renal dialysis.
90
84. (221) It is anticipated that the gold standard for the diagnosis of myocardial infarction (MI) will be
troponin.
91
85. (222) Serum complement is a group of proteins, which act as enzymes, that facilitate the
body’s immunologic and inflammatory responses.
92
86. (222) The functions of immunoglobulins are to recognize antigens and
initiate a response for destruction or neutralization of the antigen.
93
87. (222) The IgM class of immunoglobulins
is the largest in molecular size and are the most primitive.
94
88. (223) Albumin and globulin make up most of the protein in the body and can be measured together as
total protein.
95
89. (223) When serum proteins are separated by electrophoresis, the most prominent band of protein seen is
albumin.
96
90. (223) Total protein is most commonly determined by
either biuret or refractive index.
97
91. (224) If a bloody tap cerebrospinal fluid (CSF) sample is sent to the laboratory, the results will reflect
contamination of blood proteins.
98
92. (224) Dye-binding methods for testing cerebrospinal fluid (CSF) protein are preferred over turbidimetric methods because
a smaller amount of sample is needed.
99
93. (225) In order for cells to covert fatty acids into triglycerides, what other substance must be present?
Glucose.
100
94. (225) Which of the following substances make up 90 to 95 percent of the stored fats in the body?
Triglycerides.
101
95. (226) Cholesterol levels decrease in all of the following conditions, except
high animal fat diets.
102
96. (226) Cholesterol samples are normally drawn fasting even though cholesterol levels are
not significantly affected by non-fasting samples as triglycerides are.
103
97. (226) When possible, perform high-density lipoprotein (HDL) separation
on the day of collection.
104
98. (227) Specimens for triglyceride testing should not be drawn unless the patient has been fasting for at least 12 hours because triglyceride levels
are quickly affected by food in-take.
105
99. (227) A potential source of error for triglyceride testing includes using
tubes with stoppers that have been lubricated with glycerol.
106
100. (228) The three general categories for the functions of hormones are
regulatory, morphogenesis, and integrative action.
107
101. (228) The specificity of hormone-receptor complexes allow the target cell to
recognize the hormone from all other substances.
108
102. (229) Each step in the synthesis of thyroid hormones is regulated by the pituitary hormone
thyroid stimulating hormone.
109
103. (229) When collecting samples for thyroid testing, remember that although plasma samples may be used, these samples
tend to form fibrin clots after freezing and thawing.
110
104. (230) Pituitary hormones are classified based on
the portion of the gland they are secreted from.
111
105. (230) In addition to promoting protein synthesis in young mammals, growth hormone (GH) also promotes
skeletal growth.
112
106. (230) An adrenomedullary hormone that facilitates the generation of energy in response to fear, anger, or aggression is
epinephrine.
113
107. (231) The tracking of a patient’s drug concentration is known as
therapeutic drug monitoring.
114
108. (231) The phenomenon that occurs when the liver metabolizes a drug before it gets into the systemic circulation is known as the
first-pass effect.
115
109. (231) The difference between a peak and a trough sample is the
peak is drawn at a drug’s maximum absorption.
116
110. (232) When monitoring antipsychotic drugs, one of the most commonly observed requests is for
lithium.
117
111. (233) When ingested, the principle action of ethanol is
the depression of the central nervous system.
118
112. (233) Which one of the following statements best illustrates a reason for a legal blood alcohol case to be dismissed?
Technician did not follow laboratory operating instructions.
119
113. (233) When an intoxicated patient refuses to have his or her blood drawn for an alcohol test, who can authorize the sample collection anyway?
Competent authority, usually with the advise of the Staff Judge Advocate.
120
114. (233) What can cause a low ethanol result in a patient who is obviously intoxicated?
Patient drank isopropanol and you performed an enzymatic ethanol test.
121
115. (234) The problem with initial clinical findings in patients who have overdosed on acetaminophen is the
initial findings are mild and do not indication the degree of hepatic damage.
122
116. (234) When testing for an overdose of aspirin, you are actually
testing for the metabolite, salicylate, and not the original drug.
123
117. (234) Treatment for salicylate intoxication is aimed at preventing further absorption of the drug. This is accomplished by
inducing vomiting or by giving activated charcoal.
124
118. (235) The effects of poisons are either
. local or remote.
125
119. (235) Improper use of insecticides can lead to significant exposure to
heavy metals.
126
120. (235) The threshold levels for positive codeine and morphine, in urine drug testing programs, are usually adjusted to take into account the
consumption of poppy seeds in breads, cakes, and muffins.
127
121. (236) It has been theorized that cancer is a multi-stage genetic process. Which of the following represents the stages in the correct sequence?
DNA damage, chromosome breakdown, selection of successful growing mutant cells.
128
122. (236) Which of the following carcinogens could cause the initial change to the cellular DNA during the cancerous process?
All the above.
129
123. (236) Which of the following types of tumor are generally more aggressive and have a poorer prognosis?
Poorly differentiated.
130
124. (236) Which of the following is not a suggested criterion for the ideal tumor marker?
Be non-specific to the tumor studied and commonly associated with it.
131
7. What two electrolytes are components of table salt?
Sodium ions (cations) and chloride ions (anions).
132
8. What are some bodily functions regulated by electrolytes?
Electrolytes regulate water distribution (intracellular and extracellular fluids), osmotic pressure, maintain blood pH, regulate heart and other muscles, play a part in the body’s oxidation-reduction reactions, cell permeability, and nerve impulse conduction.
133
9. Why is electrolyte analysis often performed as an emergency procedure?
Because an imbalance cannot be tolerated by a patient for very long and irreversible damage or death can result.
134
In what fluids do you find sodium, potassium, chloride, and bicarbonate?
Sodium ions are the principal cations of extracellular fluid. Potassium ions make up the majority of the cations found in the intracellular fluid. Chloride and bicarbonate anions are found predominately in extracellular fluid.
135
What is osmotic pressure?
The physical force that is exerted when water passes from an area of lower ion concentration to one of higher ion concentration.
136
Why is most clinical chemistry analysis performed on serum or plasma?
Because it’s more practical to measure the extracellular ions than to measure intracellular ions.
137
In what fluids do you find sodium, potassium, chloride, and bicarbonate?
Urine, spinal fluid, and sweat.
138
14. What conditions bring on dehydration?
Sustained fever, diarrhea, inadequate fluid intake, and other clinical problems.
139
15. How do you calculate an anion gap?
By subtracting the total chloride and bicarbonate anions from the total sodium cations.
140
Given the following patient electrolyte values––sodium=130 mmol/l, chloride = 100 mmol/l, and bicarbonate = 25 mmol/l––what is the anion gap?
Anion gap = (130 mmol/l) – (100 mmol/l + 25 mmol/l)
Anion gap = 130mmol/l – 125 mmol/l
Anion gap = 5 mmol/l
141
17. What are two conditions that cause an increased anion gap?
A decrease in the unmeasured cations or an increase in the unmeasured anions.
142
18. When does an abnormal anion gap become clinically significant?
Once it has been determined that the testing and retesting was valid.
143
19. In addition to clinical diagnostic applications, how else does a laboratory technician use anion gap results?
As a quality control measure.
144
What is the major cation of extracellular fluid?
Sodium
145
2. What organ regulates sodium levels?
The kidneys.
146
3. What hormone helps to regulate sodium levels?
Aldosterone.
147
4. What is hyponatremia and what causes it?
Hyponatremia is a decreased plasma concentration of sodium that can be caused by the patient not ingesting enough sodium or sodium loss due to diarrhea, prolonged vomiting, or sweating brought on by fever
Decreased sodium levels can also be caused by metabolic acidosis (due to diabetes mellitus), renal disease, diuretics, and Addison’s disease..
148
5. What is hypernatremia and what causes it?
Hypernatremia is an increased plasma concentration of sodium that can be caused by severe dehydration, Cushing’s syndrome, insulin treatment of diabetic coma patients, and inappropriate forms of saline treatment or high sodium feedings.
149
6. How does the sodium ISE work?
The sodium ISE has a glass membrane that selectively exchanges sodium ions. As the sodium ions react with the membrane, a potential-measuring circuit between the measuring electrode and reference electrode determines a change in the electromotive force. This change is proportional to the sodium concentration.
150
7. How are indirect methods of sodium analysis affected by samples with high lipid or protein content?
Indirect samples for sodium are diluted before testing. Samples high in lipids or proteins can have these (lipids and proteins) displace some of the fluid that would normally be tested for sodium content.
151
8. Potassium is primarily what type of cation?
An intracellular cation.
152
9. How is potassium absorbed and excreted?
Potassium is absorbed rapidly in the intestinal lumen and excesses are excreted by the kidneys.
153
10. How do potassium levels affect the heart?
Too much potassium inhibits the irritability of the heart and paralyzes it so that it ceases to beat. Not enough potassium increases the irritability of the heart to the point where it ceases during a contraction.
154
11. What is hyperkalemia and what causes it?
Hyperkalemia is an increased plasma level of potassium. It occurs when potassium leaves the cells at a rate faster than the kidneys can excrete it. This overload occurs in conditions of anoxia, metabolic or renal acidosis, shock or circulatory failure, Addison’s disease, dehydration, or severe red blood cell lysis.
155
12. What is hypokalemia and what causes it?
Hypokalemia is a decreased plasma level of potassium. This condition occurs as a result of low potassium intake over a period of time, increased loss of potassium through vomiting, diarrhea, gastrointestinal problems, or long-term use of diuretics. In addition, low potassium levels are seen in cases of increased aldosterone production, causing increased excretion of potassium by the kidneys, in chronic starvation patients and post-operative patients.
156
13. How does hemolysis affect potassium analysis?
Since most of the body’s potassium is intracellular, hemolysis of a sample greatly affects the potassium level of the sample.
157
14. Chloride is an anion found in what type of fluid?
Extracellular.
158
15. Chloride is only found inside of what type of cell?
Red blood cells.
159
16. What two primary functions does chloride serve?
Maintaining osmotic pressure and acid-base balance.
160
17. What is hypochloremia and what causes it?
Decreased plasma chloride levels caused by uncontrolled diabetes (overproduction of ketoacids), renal disease (chloride lost as salts not reabsorbed), prolonged vomiting, intestinal blockage, and Addison’s disease.
161
What is hyperchloremia and what causes it?
Increased plasma chloride levels caused by dehydration, prolonged diarrhea, renal tubular acidosis, respiratory alkalosis, heavy salt ingestion, and over-treatment with saline solutions.
162
19. Chloride contamination, prior to analysis, can result from what sources?
Tap water and the use of sodium fluoride as an anti-coagulant.
163
20. What is the chloride ISE membrane made of and what medications can affect this test method?
A composite of silver sulfide and silver chloride. Medications containing bromides.
164
21. Why is bicarbonate sometimes referred to as total carbon dioxide?
Bicarbonate is a term often interchanged with others used to describe carbon dioxide levels. About 90 percent of all carbon dioxide in the bloodstream is in the form of bicarbonate.
165
22. What conditions cause increased bicarbonate levels?
Metabolicalkalosis,compensatedrespiratoryacidosis(suddenstopinbreathing––canbecausedbydrugs, blockage, or long-term pulmonary disease), or alkalosis accompanying a large potassium deficiency
166
23. What conditions cause decreased bicarbonate levels?
Metabolic acidosis and compensated respiratory alkalosis (hyperventilation—deep, rapid breathing).
167
24. What are sources of error affecting samples for bicarbonate analysis?
Blood collected in anti-coagulants other than heparin can upset the balance between the red blood cells and the plasma CO2. Allowing the sample to become exposed to room air also affects sample levels as CO2 in the sample escapes into the room air (room air has a lower CO2 concentration than blood).
168
25. What are three methods commonly used for bicarbonate analysis?
Enzymatic, colorimetric, and ISE.
169
(1) The measure of the partial pressure of carbon dioxide in the blood.
pCO2.
170
(2) The partial pressure of oxygen dissolved in blood plasma.
pO2
171
(3) The percentage of available hemoglobin that is saturated
| with oxygen.
sO2
172
(4) The ion that measures the metabolic component of the
| acid-base equilibrium.
HCO3-
173
5) Expresses the extent to which the blood is acidic or
| alkaline.
a. pH
174
2. Blood gases are used to evaluate what functions?
A patient’s ability to transport oxygen, to assess disturbances in the fluid or electrolyte balance, and to monitor problems with the lungs or kidneys (since these organs regulate the body’s acid-base balance).
175
3. What is external respiration?
The exchange of oxygen and carbon dioxide that takes place in the lungs as a person inhales and exhales.
176
What concept allows oxygen and carbon dioxide to move across the alveolar and capillary membranes?
Partial pressure helps oxygen and carbon dioxide move across the alveolar and capillary membranes through the process of osmosis.
177
5. What is internal respiration?
It is the exchange of gases (oxygen and carbon dioxide) between the plasma in the capillaries and the tissue cells.
178
6. What are oxyhemoglobin and carbaminohemoglobin and how are they transported?
Oxyhemoglobin is hemoglobin that has bound with oxygen. Carbaminohemoglobin is hemoglobin that has bound with carbon dioxide. Arterial blood carries the oxygenated blood to the tissue cells. Venous blood carries the carbon dioxide laden blood from the tissues back to the lungs.
179
7. What are chemoreceptors and what function do they play in breathing?
They are special cells adapted to excitation by chemical substances. They are sensitive to the levels of pO2 and pCO2 in the body, sending impulses to the brain to speed up or decrease breathing as needed.
180
8. What is hypoxemia and what can cause this condition?
Deficient oxygenation of the blood. It can be caused by breathing air low in oxygen, hypoventilation (from suffocation, submersion, trauma, obesity, or drug-induced respiratory failure), premature mixing of venous and arterial blood, or inability to oxygenate blood due to diffusion difficulties.
181
9. What is the difference between hypercapnia and hypocapnia?
Hypercapnia is increased pCO2 in the blood (caused by decreased alveolar ventilation), while hypocapnia is a decreased pCO2 level (caused by increased ventilation rates).
182
10. When specimens are collected for venous blood gas analysis, why should a tourniquet not be used or the fist clenched?
Because it decreases the venous pO2 and allow acid metabolites to accumulate.
183
11. Why are plastic syringes avoided when blood gas samples are collected?
Because plastic syringes can allow gases to be exchanged between the blood sample and the outside air
through the barrel wall.
184
12. Why do blood gas samples have their exposure to room air minimized and air bubbles expressed out immediately following collection?
Exposure to room air affects the blood gas levels in a sample. Exposure to room air normally increases the pO2 in the sample because the oxygen in the room air is of a higher concentration than that in the blood. Exposure to room air decreases the pCO2 because the concentration in the sample is much higher than that in room air. Air bubbles in the sample must be expressed out so that any gases in the bubbles are not allowed to affect the sample’s blood gas levels.
185
1. Why is blood pH important and how does the body regulate it?
Blood pH is important because levels outside the range of 6.8 to 7.8 are incompatible with life. The body uses a series of chemical buffers, the lungs and the kidneys to regulate pH.
186
2. What is the body’s most important buffer and why?
Bicarbonate is probably the most important buffer in the body because it is present in large amounts and can be controlled by the kidneys and the lungs.
187
3. In what forms is carbon dioxide, produced by cellular metabolism, carried in the bloodstream?
A small amount of carbon dioxide is carried in the bloodstream as carbon dioxide and carbonic acid (about 5 percent), the majority is carried as bicarbonate (about 75 percent), and the remainder (about 20 percent) is bound to hemoglobin and other plasma proteins.
188
4. How do the lungs help expel carbon dioxide?
As blood containing carbonic acid circulates through the lungs, the lungs convert the carbonic acid into carbon dioxide and water, which are expelled during exhalation.
189
5. How do the kidneys help regulate pH?
They play a major role in getting rid of excess hydrogen ions. They will either directly excrete them into the urine or take them and expel them in the form of water, sodium dihydrogen phosphate, or ammonium chloride. The kidneys also form bicarbonate, as needed, which buffers the excess hydrogen ions in the plasma.
190
6. What are acidosis and alkalosis, and how are they further categorized?
Acidosis is when the pH of the blood falls below 7.35 and alkalosis is when the pH of the blood rises above 7.45. The terms are categorized further based on what they are caused by. Respiratory acidosis and respiratory alkalosis are caused by respiratory problems while metabolic acidosis and metabolic alkalosis are caused by metabolic problems.
191
7. How does the pH meter in a blood gas analyzer differ from the typical pH meter found in a laboratory?
The pH meter in a blood gas analyzer is calibrated using two buffers that fall within the ranges compatible with life. The pH meter in a blood gas analyzer is also much more sensitive because it has to be calibrated to measure within such a narrow range.
192
8. What are some sources of error for blood pH testing?
Some blood pH testing sources of error include improper sample handling (same as for blood gas testing), use of tourniquet during sample collection, protein buildup on electrodes, bacterial contamination of the sample probe, and improper instrument temperature.
193
1. In what three states can calcium be found in the blood?
In the first state, calcium is free or ionized. In the second state, calcium is bound to plasma proteins (primarily albumin). In the third, calcium is bound to diffusible anions such as phosphate, bicarbonate, lactate, and citrate.
194
2. How do alkalosis and acidosis affect the amount of free calcium in the bloodstream?
Because calcium binds to the negatively charged sites on albumin, the rate of binding is pH dependent. Alkalosis leads to an increase in the binding of calcium and a decrease in the free calcium in the blood. Acidosis causes less calcium to bind with albumin, so there is more free calcium found in the blood.
195
3. How does calcium function as an intracellular messenger?
By binding or being released from specific intracellular proteins. When proteins bind or release calcium their structure and function change. The calcium messenger system is responsible for things such as the contraction of muscles, secretion of fluids and hormones, mitosis, and the transfer of ions across cell membranes.
196
4. How are plasma concentrations of calcium regulated?
By two substances, parathyroid hormone (PTH) and the active form of vitamin D (1,25-dihydroxy vitamin D3). The 1,25-dihydroxy vitamin D3 can increase the intestinal absorption of dietary calcium. PTH is secreted in response to low levels of calcium in the blood. The body responds by retrieving calcium and phosphate from the bones, increasing the reabsorption of calcium by the kidneys and increasing the absorption of calcium in the intestines from foods eaten.
197
5. What is hypocalcemia and how is it caused?
Hypocalcemia is a decreased level of calcium. Critically decreased levels of calcium are associated with tetany. Low calcium levels can be caused by hypoparathyroidism, vitamin D deficiency, gastrointestinal problems that block the absorption of calcium or vitamin D, chronic renal failure, magnesium deficiencies and by increased demand due to pregnancy or lactation.
198
6. What is hypercalcemia and how is it caused?
Hypercalcemia is an increased level of calcium. Primary hyperparathyroidism is the most common cause of hypercalcemia in outpatients, and malignancy is the most common cause in inpatients. It can also be caused by vitamin D overdose, ingestion of large amounts of dairy products, excessive ingestion of antacids, Paget’s disease, and chronic renal disease.
199
7. Why are anti-coagulants, such as citrate, oxalate, and EDTA, not used for collecting samples for calcium analysis?
Because they form complexes with the calcium in the sample and affect test results.
200
8. How does pH affect the binding of calcium in the blood?
When the sample pH is raised, the ionization and negative charge of the albumin is also raised, causing more calcium to bind with the albumin (thus lowering the free calcium values). Decreasing the pH has the reverse effect, decreasing the calcium bound to the albumin and increasing the free calcium values.
201
9. How are organic and inorganic phosphate found in the body?
Organic phosphate is found in soft tissues in the form of organic phosphate esters. Both organic and inorganic phosphate ions are present within the cell, but most of the phosphates are found in the cells are of the organic form. Within the cells the organic phosphate ions are incorporated into nucleic acids, phospholipids, and high-energy compounds involved in cellular integrity and metabolism. Inorganic phosphate is found in extracellular fluids and serves as part of the body’s buffer system.
202
10. How does the body obtain phosphate and how are its levels regulated?
Phosphorus is in almost everything you eat. It is absorbed by the body in the small bowel. Phosphorus is primarily excreted through the urine. The control of phosphate is closely linked to that of calcium. The regulators of calcium (PTH and active vitamin D) affect phosphate concentration. PTH stimulates the kidneys to excrete phosphate while retaining calcium. This causes an inverse relationship between calcium and phosphorus (as one goes up, the other goes down and vice versa).
203
11. What is hypophosphatemia and what kind of clinical problems might be observed with this condition?
Hypophosphatemia is a decreased level of phosphate. Severe decreases in phosphate can result in neuromuscular disturbances, hemolytic anemia, decreased oxygen released from hemoglobin, and profound muscle weakness. These conditions are normally found in patients recovering from diabetic ketoacidosis, severe respiratory alkalosis, acute alcoholism, and severe burns.
204
12. What is hyperphosphatemia and how is it caused?
Hyperphosphatemia is a increased level of phosphate. This condition is caused by chronic or acute renal failure, hypoparathyroidism, vitamin D intoxication, or hypersecretion of growth hormone. In infants and children high phosphate levels are associated with normal increased levels of growth hormone.
205
13. Why is pH important during phosphate analysis?
All the common testing methods for phosphate are based on the reaction of phosphate ions with ammonium molybdate. In order for the complex to be formed, an acidic pH is required. The pH level must be carefully controlled because a less acidic pH can result in spontaneous reduction of the molybdate complex.
206
14. Why do you avoid using anti-coagulated samples for phosphate analysis?
Because the anti-coagulants interfere with the formation of the phosphomolybdate complex in the testing procedure.
207
15. Why do you avoid using hemolyzed samples for phosphate analysis?
Because red blood cells contain high concentrations of organic phosphate esters. When the cells lyse, these esters are released and can be hydrolyzed into inorganic phosphates during storage (raising phosphate levels).
208
1. What are the functions of magnesium in the body?
Magnesium is an activator for more than 300 enzymes in the body. Its intracellular roles include phosphorylation, protein synthesis, glycolysis, cell replication, and nucleotide metabolism, and it affects neuromuscular excitability.
209
2. What is hypomagnesemia and what are some of the causes and clinical indications of this condition?
Hypomagnesemia is a decreased level of magnesium in the body. Low magnesium levels can cause tetany, impair PTH secretion, and tachycardia (abnormally fast heartbeat) and fibrillation (abnormal heart muscle contractions).
210
3. What is hypermagnesemia and what are some of the causes and clinical indications of this condition?
Hypermagnesemia is an increased level of magnesium. This condition is usually caused by an excessive intake of magnesium salts (used to relieve constipation), renal problems, severe dehydration, aldosterone deficiencies, and during therapy for pre-eclampsia and eclampsia in pregnant women. The most common signs of magnesium intoxication are neuromuscular symptoms. Deep tendon reflexes disappear and breathing rates can slow or stop. High magnesium levels can also cause cardiac arrest.
211
4. Why is hemolysis avoided in magnesium samples?
Red blood cells contain high levels of magnesium.
212
5. Why is lithium analysis usually requested?
As a tracking mechanism for lithium carbonate treatments. Lithium carbonate is used to treat the manic phase of affective disorders, mania, and manic-depressive illness.
213
6. What are the signs of lithium intoxication?
Early signs of lithium intoxication (about 2 mmol/l) include apathy, sluggishness, drowsiness, speech difficulties, and twitching. Severe intoxication (about 2.5 mmol/l) is characterized by muscle rigidity, hyperactive deep tendon reflexes, and epileptic seizures.
214
7. When performing flame emission photometry for lithium analysis, what two substances are used as the internal standards?
Cesium or potassium.
215
1. What process does the body use to regulate iron and why is this unique?
Intestinal absorption (and to a lesser degree, the bloodstream), which is unique because most other elements are regulated by excretion.
216
2. Why do adult females typically suffer greater losses of iron than do adult males?
Female losses are greater due to normal menstruation as well as the burdens associated with pregnancy.
217
3. Why must laboratories establish local reference ranges for iron?
Because of the wide-ranging differences found between commercial methods.
218
4. Name a potential source of error to consider when conducting iron studies.
Because iron is widely distributed in the environment great care must be taken to avoid contamination of testing equipment or reagents.
219
5. In the total iron binding capacity (TIBC) test, why is iron added to the sample?
To saturate the transferrin iron binding sites.
220
6. What are potential sources of error in ferritin assessments?
In conditions such as chronic infections, rheumatoid arthritis, renal disease, heart disease and several types of malignancies, that are present with concurrent iron deficiency, the ferritin levels may be within normal limits, but would still be considered as increased because of the other underlying condition(s).
221
7. Why are the effects of hereditary hemochromatosis manifested in men often twenty years or more before the same effects are seen in women?
Because of the protection from menstruation. Women are typically affected post-menopausal.
222
8. What is the treatment regimen for hemochromatosis?
Periodic therapeutic phlebotomy.
223
1. Describe the location and appearance of the liver.
It is located in the upper right quadrant of the abdomen. The upper portion of the liver is overlaid by the lungs and diaphragm. The lower portion of the liver overlaps the stomach and intestines. The liver is covered by a collagenous capsule, and although it appears to be divided into a right and left half, it is actually divided into four lobes.
224
2. What are the two sources of blood to the liver?
The portal vein and the hepatic artery. The portal vein carries blood from the capillary bed of the digestive system to the liver and the hepatic artery carries well-oxygenated blood to the liver.
225
3. What are the liver’s functions for providing energy to the body?
The liver converts glucose into glycogen for storage. When energy is needed, the liver converts the glycogen back into glucose for release into the body. The liver maintains the release of glucose as a steady process, but in emergencies can release massive amounts of glucose in response to epinephrine.
226
4. What are some of the clearinghouse functions of the liver?
The liver disposes of worn out red blood cells by breaking them down into different components, some of which are stored for future use, and others, which are excreted by the kidneys. The liver also filters and destroys bacteria, neutralizes poisons, and regulates sex hormone levels.
227
5. Where is bile formed, what route does it take, and what is its function?
Bile is formed in the liver and flows into the gallbladder where it is concentrated and stored. Bile is released from the gallbladder into the intestines. In the intestines, bile (in the form of bile salts) breaks down large fat globules into smaller ones that can be acted on by fat-splitting enzymes.
228
6. What are some of the metabolism functions that take place in the liver?
The liver plays a key role in the metabolism of carbohydrates. The liver is also responsible for synthesizing all plasma proteins except for gamma globulins. Other proteins formed in the liver are proteins for blood coagulation. The liver is also active in the anabolism and catabolism of lipids.
229
7. What other substances are stored in the liver besides glycogen?
The liver stores vitamins A, D, and B12. It stores iron in significant amounts. And, it temporarily stores small amounts of proteins and lipids.
230
8. Where is bile stored?
In the gallbladder.
231
9. How does the liver help protect the body?
By destroying foreign material (such as bacteria). Kupffer cells in the liver are phagocytic cells that remove foreign material from the blood. The liver also detoxifies toxic chemicals by converting them to less toxic forms or by making them water-soluble so they can be excreted by the kidneys.
232
10. How does the liver help with blood circulation and the coagulation process?
It serves as a storage area for blood and helps regulate blood volume. It also serves to mix blood from the portal system with blood in circulation to the rest of the body. It continuously synthesizes protein-clotting factors, as many of these factors have a short life span and need to be replaced regularly.
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(1) Liver inflammation caused by a viral agent.
Viralhepatitis.
234
(2) Hepatitis that is transmitted most commonly through
| the fecal oral route.
Hepatitis E virus.
| Hepatitis A virus.
235
(3) Hepatitis that is transmitted through the parenteral
| route.
Hepatitis D virus.
Hepatitis C virus.
Hepatitis B virus.
236
(4) It may take up to 3 months for its antibodies to reach
| detectable levels.
Hepatitis C virus.
237
(5) Rare in the U.S. and Europe.
Hepatitis E virus.
238
(6) Occurs in coinfection and superinfection forms.
HepatitisDvirus.
239
(7) Caused by overindulgence of ethanol.
Alcoholic liver disease.
240
(8) Damage to the hepatic cells can be unpredictable.
Hepatic toxicity due to drugs.
241
(9) Creates a back up in the excretion of bilirubin.
Blockage or obstruction.
242
1. From what is bilirubin derived and how does it get into the hepatic cells?
It is derived when old red blood cells are phagocytized and the hemoglobin released is broken down. Bilirubin is bound to albumin as it leaves the MPS, and this complex attaches to the hepatocyte membranes. The bilirubin then detaches from the albumin carrier and is transported into the hepatic cells.
243
2. Define conjugated bilirubin and unconjugated bilirubin.
Conjugated bilirubin is bilirubin that has been joined with glucuronic acid inside of the hepatocytes. Bilirubin that has not been bound to glucuronic acid is called unconjugated bilirubin.
244
3. What are the bile pigments that are the major pigments of the stool?
Urobilin, stercobilin, and mesobilin.
245
4. What is jaundice and how is it characterized?
Jaundice is a disturbance in the flow of bile. It is characterized by the deposit of a yellowish pigment in the eyes and skin. When this condition is detectable visually, the bilirubin levels are well above normal.
246
(1) This condition is caused when too many red blood cells are being destroyed.
Excess bilirubin in the liver.
247
(2) A congenital defect in the transport system that carries bilirubin to the hepatic cells.
. Gilbert’s syndrome.
248
(3) Known as Crigler-Najjar syndrome, more than half of the patients die within 1 year of birth due to this.
. Enzyme deficiency.
249
(4) In newborns, this condition is caused because the transferase enzyme system is not fully developed.
Impaired conjugation.
250
6. What is the cause of hemolytic disease of the newborn?
It is caused by a blood group incompatibility between the mother and the fetus. If the mother has been sensitized previously, the IgG antibodies from the mother cross the placenta and cause the destruction of the infant’s red blood cell membranes.
251
7. How do excretion disturbances increase serum bilirubin levels?
Obstruction or impairment of the excretion of bile into the intestines will cause the concentration of bilirubin to build up in the hepatocytes and be regurgitated into the bloodstream. This condition is further worsened because the increased levels of bilirubin in the hepatocytes also cause a slow down in the bilirubin transport system, further increasing the bilirubin levels in the bloodstream.
252
8. What are intrahepatic and posthepatic excretion disturbances?
Intrahepatic disturbances are disorders that take place within the liver, caused by damage or destruction of the liver cells due to viral hepatitis, toxins, or liver cirrhosis. Posthepatic disturbances are those that cause the obstruction of the flow of bile into the intestines, caused by stones in the gallbladder or bile ducts as well as tumors or carcinomas.
253
9. Hemolytic conditions cause an increase in what type of bilirubin?
Unconjugated bilirubin.
254
10. What is the principle of the modified Jendrassik-Grof method of total bilirubin analysis?
The serum sample is mixed with a slightly acidic solution of caffeine and sodium benzoate. These chemicals accelerate the diazotization of the unconjugated bilirubin. Diazotized sulfanilic acid reacts with both forms of bilirubin to form an azo dye. When alkaline tartrate (with a pH of 13) is added, the azobilirubin is converted to a blue color, which is measured at 600 nm. The total bilirubin concentration is proportional to the amount of color produced.
255
11. What are the principles of testing for conjugated bilirubin and how the unconjugated bilirubin is determined?
To test for conjugated bilirubin, a serum sample is mixed with diazo reagent without accelerators. Only conjugated bilirubin will react under these conditions within the first 5 minutes. At the 5-minute mark, ascorbic acid is added to decompose the excess diazo salt and halt the reaction. The solution is then read at 600 nm and the color produced will be proportional to the amount of conjugated bilirubin in the sample. To determine the unconjugated bilirubin, the conjugated bilirubin result is subtracted from the total bilirubin result.
256
12. Why should fasting samples be used for bilirubin testing and hemolyzed samples be avoided?
To avoid lipemia in the sample. Hemolyzed samples should not be used because hemolysis can cause falsely low values with diazo methods.
257
13. What special handling do bilirubin samples require and why?
Because bilirubin is light sensitive and will break down if exposed to either artificial or natural light, protect samples from direct exposure to light as soon as possible after collection. The sensitivity of bilirubin to light is also affected by temperature. Samples are stable for up to 3 days if refrigerated at low temperatures and kept in the dark. Samples kept in the dark and frozen at –70°C will be stable for up to 3 months.
258
14. In healthy newborns, when are adult bilirubin levels reached?
By the time the infant is 1 month old.
259
1. During fasting conditions, what tissues rely on glucose exclusively for energy?
The brain, erythrocytes, platelets, leukocytes, and kidney medulla.
260
2. Carbohydrates are made up of what three elements and what is unique about their chemical formulas?
Carbohydrates are made up of carbon, hydrogen and oxygen. Carbohydrates approximately contain one molecule of water for every carbon atom.
261
3. How are carbohydrates classified?
Carbohydrates are classified based on the number of simple sugars that can be broken down into during the process of hydrolysis.
262
4. What are monosaccharides, disaccharides, and polysaccharides?
Monosaccharides are the simplest of the sugars and cannot be hydrolyzed into simpler structures. Disaccharides are sugars that will yield two monosaccharides when hydrolyzed. Polysaccharides are sugars with more than two saccharide groups.
263
5. What is the function of salivary amylase?
Starches and glycogen are partially digested by salivary amylase to form maltose.
264
6. After carbohydrates are digested, where are monosaccharides absorbed and at what rate?
They are absorbed primarily in the small intestines. The rate of absorption is determined by the selectivity of the intestinal mucosa (different monosaccharides absorb at different rates).
265
7. Monosaccharides are metabolized to perform what three processes?
(1) To be used for energy production by conversion to carbon dioxide and water.
2–51
(2) To be converted to glycogen for storage in the liver or converted to triglycerides for storage in the adipose tissue.
(3) To be converted into other products such as keto acids, amino acids, or proteins.
266
8. Glycolysis, in the muscle tissue, serves what purpose?
To supply energy to the muscle tissues.
267
1. Other than glucose, which monosaccharides are normally found in bodily fluids in significant amounts?
None.
268
2. Define glycogenolysis and gluconeogenesis.
Glycogenolysis is the breakdown of stored glycogen into glucose for release into the blood. Gluconeogenesis is the formation of glucose in the body from non-carbohydrate sources such as amino acids, glycerol, or lactate.
269
(1) This hormone is secreted in the pancreas and stimulates the uptake of glucose into muscle.
Insulin.
270
(2) This hormone promotes the conversion of glucose into glycogen or fat for storage.
Insulin.
271
(3) This hormone has its effects regulated by plasma glucose levels and its effects are confined to the liver.
Glucagon.
272
(4) This hormone stimulates gluconeogenesis and increases the catabolism of protein and fat.
Cortisol.
273
(5) Physical or emotional stress increases the production of this hormone that in turn increases glucose levels.
Epinephrine.
274
(6) This hormone stimulates gluconeogenesis, enhances lypolysis, and antagonizes insulin-stimulated glucose uptake.
Growth hormone.
275
(7) This hormone affects glucose levels by increasing the rate of gastric emptying and intestinal glucose absorption.
Thyroxine.
276
(8) This hormone inhibits the release of growth hormone as well as the secretion of glucagon and insulin.
Somatostatin.
277
Define hyperglycemia and hypoglycemia.
Hyperglycemia is an increased plasma glucose while hypoglycemia is a decreased plasma glucose.
278
What are the long-term effects of diabetes mellitus?
They include permanent damage to the eyes with the potential loss of vision, the kidneys leading to renal failure, the leg including foot ulcers and possible amputations.
279
By what criteria is diabetes now categorized?
The patient is categorized by the cause of their disease rather than the treatment of it.
280
What are the four categories of diabetes?
Type 1 diabetes, Type 2 diabetes, Other specific types, and Gestational diabetes mellitus.
281
What causes Type 1 diabetes?
It is an immune mediated diabetes, the patient produces autoantibodies that destroy their own insulin producing cells.
282
What causes Type 2 diabetic patients to have hyperglycemia?
Their hyperglycemia range from disorders that cause insulin resistance along with decreased insulin production to problems with insulin secretion from the pancreas combined with insulin resistance.
283
The other specific types diabetes category includes patients with what conditions?
Genetic defects of the beta cells or insulin receptor sites, diseases of the pancreas, hormonal disorders, and drug, chemical or infectious agent destruction of the beta cells.
284
Define gestational diabetes mellitus (GDM).
Any degree of glucose intolerance that is initially recognized during pregnancy.
285
What are the criteria used when screening for GDM?
Performed between the 24th and 28th week of gestation. Patient should meet one or more of the following criteria: 25 years of age or older, less than 25 years of age and obese or greater than 20 percent over their desired body weight, family history of diabetes, and member of an ethnic group with a high prevalence of diabetes.
286
A patient can loss consciousness when their plasma glucose levels fall below what level?
When levels drop below 40 mg/dl in an adult, the patient may lose consciousness.
287
How do hormonal and hepatic problems cause hypoglycemia?
Hormonal reasons include an overabundance of insulin caused by an overdose of injected insulin, failure of the patient to eat after an insulin dose, or an increased production of insulin by the pancreas. Other hormonal causes include a deficiency of glucagon or cortisol. Hepatic causes include decreased stores of glycogen due to prolonged fasting, hepatocellular damage, acute drug toxicity, or genetic defects in the liver, such as von Gierke’s disease.
288
Briefly describe the three criteria used to diagnose diabetes mellitus.
Symptoms of diabetes plus a casual glucose concentration (CGC) greater than or equal to 200 mg/dl, fasting plasma glucose (FPG) of greater than or equal to 126 mg/dl, or 2 hour postload glucose (2-h PG) of greater than or equal to 200 mg/dl during an oral glucose tolerance test (OGGT).
289
Define normoglycemia, and impaired fasting glucose (IFG).
Normoglycemia is defined as plasma glucose levels <110 mg/dl in a FPG and a 2-h postload value of <140 mg/dl in the OGTT. FPG levels greater than or equal to 126 mg/dl are abnormal and are defined as an impaired fasting glucose (IFG).
290
When performing an oral glucose tolerance test (OGTT), how much glucose is given to the patient after the fasting sample has been collected?
75g.
291
How do cerebrospinal fluids (CSF) glucose levels correlate to blood glucose levels and what is CSF glucose analysis used to diagnose?
The concentration of glucose in CSF is about 60 to 75 percent of that in a patient’s plasma. CSF glucose analysis is useful in helping to diagnose bacterial meningitis.
292
Why are serum samples for glucose analysis centrifuged and separated shortly after they have clotted?
Due to glycolysis in the sample. Glycolysis can decrease the glucose in a sample by as much as 5 to 10 mg/dl for every hour the sample is left uncentrifuged at room temperature.
293
What is one advantage of the hexokinase method over the glucose oxidase method for glucose analysis?
It is less likely to be affected by medications or other constituents in the plasma.
294
In the glucose oxidase method, what two products can be measured to determine the concentration of glucose in the sample?
The glucose level in the sample is proportional to the oxygen consumed in the reaction or the amount of hydrogen peroxide produced.
295
Why should you NOT use the glucose oxidase method for urine glucose analysis?
Because urine contains high concentrations of substances (such as uric acid), which produce falsely, low results with the glucose oxidase method.
296
1. Why are enzymes defined as biological catalysts?
Because they cause reactions to take place in the body.
297
2. How may genetic defects affect enzyme activity?
Enzymes are proteins and are synthesized under the control of specific genes. Deficiencies in enzyme proteins or enzyme activity are sometimes tracked back to genetic defects.
298
3. Under the system established by the Enzyme Commission (EC), what are the enzyme’s systematic name and trivial name?
The systematic name is used to describe the nature of the reaction catalyzed by the enzyme. The trivial name is the one that has been simplified for everyday use.
299
4. What is the significance of the four-number code used by the EC in its classification system?
The first number sequence designates the class that the enzyme belongs to. The next two number sequences indicate the subclasses of the enzyme. The final number in the sequence is a unique serial number for that specific enzyme in its subclass.
300
(1) The speed of the reaction is directly proportional to this.
Concentration of the enzyme.
301
(2) At this point in a reaction, the substrate has reached an excess, so it no longer influences the reaction.
Zero order reaction.
302
(3) Enzyme activity can be irreversibly ceased by raising this factor too high.
Temperature.
303
(4) Some enzymes are characterized based on this factor when describing their activity.
pH.
304
(5) These items cause a decrease in the amount of enzyme
| activity by resembling the enzyme’s substrate.
Competitive inhibitors.
305
(6) These items cause a decrease in the amount of enzyme
| activity by altering the configuration of the enzyme.
Non-competitive inhibitors.
306
(7) Reactions proceed faster when more enzyme molecules are
| present to bind with the abundant amount of substrate.
Mass action effect.
307
What is the function of amylase and what organs secrete it?
Aids in the breaking down of carbohydrates into simpler sugars; pancreas and salivary glands.
308
2. Why is pancreatic amylase the primary source of amylase in the intestines?
Because salivary amylase is deactivated by stomach acids as it travels through the stomach.
309
3. In what other tissues and fluids is amylase found?
Amylase is found in semen, milk, tears, fallopian tubes, testes, ovaries, striated muscle, and lungs.
310
4. What is the significance of the P3 amylase isoenzyme?
The P3 isoenzyme peak frequently occurs in patients suffering from acute or chronic pancreatitis or renal transplants.
311
5. When the pancreatic ducts or salivary glands are blocked, how does this effect serum amylase level?
Increased serum amylase level will be observed when there is a blockage in the secretion of amylase from either source.
312
6. When serum amylase levels are increased due to pancreatic problems, for how long will peak levels occur and when will the levels return to normal?
Following acute pancreatitis, serum amylase levels will peak after about 24 hours and will return too normal in 2 to 3 days.
313
7. Following an acute pancreatitis, how do urine and serum amylase levels compare?
Increased urinary excretion of amylase persists longer than the increased serum levels , generally not returning to normal until 7 to 10 days after the attack.
314
8. How does liver damage affect serum amylase levels?
Acute or chronic hepatocellular damage can cause decrease levels. Note that amylase is not a sensitive liver function test.
315
9. What is the specimen of choice for amylase analysis and how stable is it?
Serum is the specimen of choice. Anticoagulants, except for heparin, can inhibit amylase activity by as much as 15 percent. Samples are stable for up to 1 week at room temperature and up to 2 months if refrigerated.
316
10. What are the three starch-based methods used for amylase analysis, and what is the principle of each method?
The amyloclastic assays measures the disappearance of the starch substrate. The amount of starch hydrolyzed is read photometrically and compared to a starch-iodine calibration curve. Saccharogenic assays determine amylase activity by measuring the reducing sugars produced as a result of enzymatic action. Chromogenic assays determine amylase activity by using a dye-labeled amylase substrate. These substrates are insoluble and, when acted upon by the enzyme, release dye that then becomes soluble. The released dye is then measured photometrically.
317
1. What does the alkaline signify in the name alkaline phosphatase (ALP), and what function does ALP serve?
Alkaline signifies that this enzyme’s activity is increased in an alkaline environment; to help with lipid transport in the intestines and with the calcification process in the bone.
318
2. Where are the highest concentrations of ALP found?
In the liver and bones.
319
3. ALP analysis detects disorders in what areas of the body?
Liver and bone. Isoenzymes of ALP are used to distinguish these conditions.
320
4. In extrahepatic conditions, such as biliary tree obstructions, what changes occur in serum ALP levels?
ALP levels will increase as much as 10 to 12 times the upper normal limit. Levels will return to normal shortly after surgical removal of the obstruction.
321
5. How high will ALP levels increase during intrahepatic obstruction of the bile flow?
ALP levels can increase up to 2 to 5 times the upper normal limit.
322
6. How does Paget’s disease effect serum ALP levels?
Values as high as 10 to 25 times the upper normal limit are common in Paget’s disease.
323
7. How does the patient’s age effect normal ALP ranges?
Normal bone growth in children will also produce elevated ALP results. Growing children will normally have levels 1.5 to 2.5 time higher than that of normal adults.
324
8. How does pregnancy effect ALP levels?
During the third trimester of pregnancy, an increase in ALP levels may be observed. This increase is usually 2 to 3 times the normal upper limit with the additional enzyme being produced by the placenta. Upward or downward trends can indicate pregnancy complications.
325
9. What conditions cause decreased serum ALP levels?
During hypophosphatasia and deficiencies of thyroid hormones and vitamin B12.
326
10. If a sample for ALP testing has been frozen, how soon after thawing can it be analyzed and why?
Thaw and then stored at room temperature for 18 to 24 hours before testing. This allows for full enzyme reactivation. During freezing, enzyme activity is temporarily inactivated.
327
11. What are the two methods used for ALP isoenzyme analysis, and what is the principle of each method?
Electrophoretic methods are used to separate serum samples into recognizable patterns to detect the isoenzymes. Heat-inactivation methods differentiate the isoenzymes based on their stability when exposed to heat.
328
1. Why are alanine aminotransferase (ALT) and aspartate aminotransferase (AST) analysis routinely requested?
Because of their immediate value in diagnosing liver disorders.
329
2. When are ALT and AST observed in the urine?
When a patient is suffering from kidney lesions.
330
3. Of the two enzymes, ALT and AST, which is primarily used to diagnose intracellular hepatic diseases? Why?
ALT, because it is the more specific of the two (ALT and AST) for liver functions.
331
4. Where, in the body, is AST found?
AST is found in practically every body tissue, including red blood cells. The concentration is particularly high in cardiac muscle and the liver. Moderate levels are found in skeletal muscle and the kidneys. The concentration of AST in all other tissues is very low.
332
5. What is AST analysis primarily used to diagnose?
Liver damage and in determining the extent of injury to cardiac muscle.
333
6. What happens to ALT and AST levels in patients that are suffering from a condition that causes hepatic necrosis?
Their levels will increase even before the patient shows any clinical signs of the disease. Values will peak between the 7th and 12th day of illness and levels will run 20 to 50 times that of normal levels. If recovery is uneventful, levels will return to normal after 3 to 5 weeks.
334
7. What happens to ALT and AST levels following a myocardial infarction?
AST levels will increase. AST levels do not reach an abnormal level until 6 to 8 hours after the onset of chest pain. AST levels will peak after 18 to 24 hours following the infarction. Levels will return to normal by the fourth or fifth day, providing no other attacks occur. ALT levels will remain at or near normal because the levels of ALT in the heart muscle are only a fraction of those of AST.
335
8. How do hemolyzed samples alter ALT and AST results?
They would be falsely elevated. ALT activity in red blood cells is 7 times that of serum and AST levels are 15 times that of serum.
336
9. What course of action is taken when samples for ALT or AST testing exceed analyzer linearity?
They should be diluted and rerun. Saline may be used, but an albumin solution is preferred.
337
10. What are the reactions that take place during ALT analysis?
ALT catalyzes transfers of an amino group from alanine to α-ketoglutarate, forming pyruvate and glutamate. The rate of formation of pyruvate is determined by coupling this reaction with lactate dehydrogenase. In the second part of the reaction, the pyruvate is converted to lactate and the reaction is read at 340 nm. The change in absorbance indicates the amount of ALT present in the sample.
338
11. What are the reactions that take place during AST analysis?
AST catalyzes transfers of an amino group from aspartate to α-ketoglutarate to form oxaloacetate. Oxaloacetate and NADH are then coupled with malate dehydrogenase. This reduces oxaloacetate to malate, oxidizes NADH to NAD+. The decrease in absorbance, read at 340 nm, reflect the amount of AST present in the sample.
339
1. What is the function of gamma glutamyltransferase (GGT) and where, in the body, is it found?
Catalyzes the transfer of a gamma-glutamyl group to a peptide, amino acid, or even water. It is found in all cells except those in the muscle.
340
What is the clinical significance of GGT in regard to hepatobiliary disease?
GGT is one of the most sensitive enzymatic indicators of hepatobiliary disease. While GGT is elevated in all forms of liver disease, it is highest in cases of intrahepatic or post-hepatic biliary obstruction, often reaching 5 to 30 times that of normal levels. GGT is considered a better indicator of obstructive jaundice than AST, ALT, or ALP because it increases earlier and persists longer than other enzymes.
341
3. How does the consumption of drugs or alcohol affect GGT levels?
Values will increase quickly even after a small intake of alcohol. Its levels are also affected in patients whose bodies are attempting to detoxify certain drugs.
342
4. How do GGT levels help distinguish between liver and bone disease?
GGT levels are normal during skeletal disease, while ALP levels are elevated. This implies that the problem is in the bones.
343
5. How do GGT levels help distinguish liver disease from muscle or hemolytic conditions from muscle disease?
5. GGT levels are not elevated during muscular disease, while AST levels are elevated.
344
6. Why are GGT values higher in males than in females?
Because there are high levels of GGT in the prostate; normal male GGT values are higher than female values.
345
7. What do you suspect when there are increased GGT levels in patients with malignancies?
That the disease has metastasized to the liver.
346
8. Explain the principle used for GGT analysis.
In the presence of GGT and a buffer, γ-glutamylglycylglycine and ρ-nitroaniline are produced. An increase in absorbance due to the formation of ρ-nitroaniline in the reaction is measured spectrophotometrically at 405 nm and the amount of GGT in the sample is calculated.
347
1. Why is the diagnostic value of a total lactate dehydrogenase (LD) level questioned as opposed to LD isoenzyme levels?
Because it is so widely distributed in the body, the diagnostic value of an increase in total LD concentration is questionable. It indicates an ongoing disease process but offers little specifics on the problem’s origin. By analyzing LD isoenzymes we can pinpoint the cause of the increased LD activity.
348
2. What are the two types of LD isoenzyme peptide chains and what do they represent?
The M-type is typical of skeletal muscle while the H-type is from cardiac muscle.
349
3. A patient had a myocardial infarction (MI) and exhibits an increased LD1 isoenzyme level. What is the peptide chain structure for this isoenzyme?
The peptide chain structure of LD1 is HHHH (H4).
350
4. A patient with progressive muscular dystrophy exhibits an increased LD5 isoenzyme level. What is the peptide chain structure for this isoenzyme?
The peptide chain structure for LD5 is MMMM (M4).
351
5. How does pH affect the LD reactions?
The direction of LD enzymatic reactions is dependent on pH. In an alkaline pH, LD converts lactate to pyruvate. In a neutral pH environment, LD converts pyruvate back to lactate.
352
6. Why are LD levels especially useful in a delayed MI diagnosis?
LD levels will rise later than that of the enzyme creatine kinase. This later rise is very useful in the diagnosis of patients who complain of chest pains that occurred 3 or 4 days ago.
353
7. What is meant by flipped LD level?
Normal LD isoenzyme pattern is: LD2 levels are greater than those of LD1. A flipped LD level has LD1 levels greater than those of LD2.
354
8. How do deficiencies of folate or vitamin B12 affect LD levels?
In megaloblastic anemias resulting from a deficiency of folate or vitamin B12 can cause red blood cell precursors in the bone marrow break down. As these cells break down, they release large quantities of LD1and LD2 isoenzymes. After appropriate treatment, LD levels quickly return to normal.
355
9. How do liver and renal diseases effect LD levels?
Increased LD activity can be observed during liver disease, but the aminotransferase (ALT and AST) activity is much more increased. In renal diseases, the increased LD levels do not correlate very well with the other parameters of the disease, and isoenzyme patterns can resemble normal serum patterns.
356
10. How do malignant diseases effect LD levels?
Patients with malignant diseases often show an increase in serum LD activity; however, the LD activity is too erratic to be useful as a diagnostic tool. LD activity is useful, though, in monitoring the effectiveness of chemotherapy against the tumor.
357
11. Why will LD5 levels decrease in the later stages of progressive muscular dystrophy?
Most of a patient’s muscle mass containing LD5 has been lost, so LD levels will decline.
358
12. How does spinal fluid LD isoenzyme analysis in patients with bacterial meningitis or viral meningitis compare?
Patients with bacterial meningitis will have granulocytosis and their spinal fluid will show an increase in the LD4 and LD5 isoenzymes. Patients with viral meningitis will have lymphocytosis and an increase in the LD1 and LD3 isoenzymes.
359
13. Why avoid hemolyzed samples for LD testing, and why don’t you freeze LD samples?
Red blood cells have a LD level 150 times that of serum, and ruptured cells will cause falsely elevated results. Freezing samples should be avoided because some of the LD isoenzymes are significantly affected by low temperatures. LD4 and LD5 lose all activity if frozen.
360
14. What are the forward and reverse reactions used during LD analysis?
In the forward LD reaction, the enzyme LD converts lactate to pyruvate while reducing NAD+ to NADH. The rate of increase in the absorbance of NADH at 340 nm is proportional to the LD activity of the sample. In the reverse reaction, pyruvate is converted back to lactate. Here, the NADH is oxidized back to NAD+ and the decrease in absorbance is measured.
361
15. What method is used for LD isoenzymes analysis?
Electrophoresis.
362
1. What are the forward and reverse reactions of creatine kinase (CK), and what part does pH play in controlling these reactions?
The forward reaction of creatine kinase (CK) and magnesium ions catalyze the transfer of a phosphate from adenosine triphosphate (ATP) to creatine, forming creatine phosphate and adenosine diphosphate (ADP). In the reverse reaction, takes creatine phosphate and ADP, in the presence of CK and magnesium ions, will yield creatine and ATP. The direction of the reaction is dependent on the pH of the reaction media. An alkaline pH favors the forward reaction, while a neutral pH favors the reverse reaction.
363
2. What do M and B subunits signify?
The M signifies a polypeptide subunit for muscle and the B signifies a polypeptide subunit for brain.
364
3. Where are the CK isoenzymes predominately found in the body?
CK-BB is found in the brain, CK-MB is found in the cardiac muscle, and CK-MM is found in the skeletal muscle.
365
4. How is CK analysis used to assess MI patients?
In a patient with a MI, CK activity will begin to increase 3 to 6 hours after a MI and will usually reach its maximum level about 24 hours after onset. As long as no further MI’s occur, CK levels will normally return to normal within 2 to 3 days. CK-MB determinations are the single best test for early diagnosis of a MI.
366
5. Most of the circulating CK in normal serum is CK-MM. What conditions cause an increase in this isoenzyme?
The cause is usually some kind of stress or injury to skeletal muscle. Vigorous exercise, multiple intramuscular injections, electroconvulsive therapy, and surgery can cause a rise in CK-MM activity. Muscular diseases, such as progressive muscular dystrophy, can also cause a dramatic rise in CK-MM levels.
367
6. What types of conditions can cause an increase in CK-BB activity?
Patients suffering from head trauma will normally show increased activity. Diseases that cause swelling to the brain, such as Reye’s syndrome in children, can also cause increased CK-BB levels.
368
7. You have just received a non-hemolyzed serum sample collected 2 hours ago. Can you use this sample for CK analysis?
This sample is suitable for CK analysis.
369
8. Why is the reverse CK reaction most commonly used for CK analysis?
Because this reaction proceeds at a much faster rate than the forward reaction.
370
9. Describe the reverse CK reaction for CK analysis.
In the reverse reaction, creatine phosphate and adenosine diphosphate (ADP) in the presence of CK will yield creatine and adenosine triphosphate (ATP). The ATP produced is then added to glucose in the presence of hexokinase. This reaction yields glucose–6-phosphate (G–6-P) and ADP. The G–6-P that results is then added to nicotinamide-adenine dinucleotide phosphate (NADP+) in the presence of glucose– 6-phosphate dehydrogenase (G6PD), resulting in 6-phosphogluconate, NADPH, and H+. The rate of formation of NADPH is a measure of the concentration of CK activity in the sample.
371
10. Describe the electrophoretic method for CK isoenzymes analysis.
In electrophoresis, the CK isoenzymes are separated on agar, agarose, or cellulose acetate. The isoenzyme bands are then treated with a mixture, prompting the reverse reaction. The NADPH formed by this reverse reaction can then be visualized under fluorescent or visible light and quantified by scanning on a densitometer or fluorometer.
372
11. Describe the ion-exchange method for CK isoenzyme analysis.
Ion-exchange methods have been used to separate CK isoenzymes using either batch adsorption or column chromatography using various mediums. The basic process involves the CK isoenzymes adsorbing onto the medium, usually a gel. The gel is then washed, and the CK isoenzymes are then eluted, using TRIS buffers with varying sodium chloride concentrations. A major drawback to this method is that the CK isoenzymes can be greatly diluted during the elution process, requiring the fractions to be concentrated after collection or some other method used to reduce the dilution effect.
373
12. Describe the immunological methods for CK isoenzyme analysis.
Immunological methods require the use of specific antisera against either the M or B subunits in order to measure the CK isoenzymes. When measuring CK-BB, an anti-CK-M sera inhibits any M subunits so that only CK-BB activity is measured. When measuring CK-MM, an anti-CK-B sera inhibits any B subunit activity so only CK-MM activity is measured. Determining the activity of CK-MB presents a unique challenge. In order to determine CK-MB activity, a sandwich technique is often used. In this technique, two antibodies having different affinities for different parts of the CK-MB molecules are used sequentially. This method provides an estimate of CK-MB activity because neither CK-MM nor CK-BB will react with both antibodies.
374
1. Why are acid phosphatase (ACP) and prostate specific antigen (PSA) analysis used to diagnose and monitor prostatic cancer?
Because they are very specific for the prostate. Acid phosphatase (ACP) is an enzyme that has its highest concentrations in the prostate. Prostate specific antigen (PSA) is a glycoprotein only found in prostatic epithelial cells.
375
2. What is the problem associated with using ACP for the detection of prostate phosphate?
ACP levels often remain normal until the cancer metastasizes. Only after the cancer spreads to blood capillaries, lymph channels, or other tissues will ACP activity rise dramatically.
376
3. The majority of the ACP found in normal serum comes from what cell?
From the osteoclasts.
377
4. What conditions cause increased ACP levels in women?
When they are suffering from bone diseases such as Paget’s disease or the malignant invasion of the bones by cancers such as breast cancer.
378
5. Why is PSA such a good tumor marker, and why is it replacing ACP as a screening procedure for the detection of prostatic cancer?
PSA is an antigen that can be detected in all males. The levels of this antigen are greatly increased in patients who have prostatic cancer. The higher the antigen level the greater the tumor burden. Because PSA is only produced by the prostate, this makes this glycoprotein an excellent tumor marker. PSA is replacing ACP as an early screen for prostate cancer because it is much more sensitive in determining the early stages of the disease.
379
6. How are samples for ACP testing stabilized?
By the addition of commercially available disodium citrate monohydrate tablets or by adding acetic acid to the serum until the pH reaches a level of 5.4, the level at which the enzyme is stable. At this pH, the sample is stable for several hours if left at room temperature and up to a week if refrigerated.
380
7. How is ACP activity determined when using thymolphthalein monophosphate as a substrate?
Thymolphthalein monophosphate is hydrolyzed by prostatic ACP at a pH of 5.4. The reaction is stopped after 30 minutes by adding a sodium hydroxide-sodium carbonate solution. This develops an alkaline color with liberated thymolphthalein. The reaction is read at 595 nm, and the absorbance of the solution corresponds to the ACP activity.
381
6. What is the immunological method that sandwiches ACP in order to determine its level?
These methods determine their specificity for the source of the ACP based on the specificity of their antiserum. In most of these methods, the total ACP activity is first measured, and then, a specific antiserum is used to capture the prostatic ACP. The difference between the two measurements determines the prostatic enzyme’s activity.
382
1. What controls the rate of lipase action?
The rate of lipase action is dependent upon the amount of surface area available, with the more surface area available the faster the rate of lipolysis
383
2. Why is the specificity of lipase to diagnose pancreatitis reduced?
Lipase can be elevated by a variety of other conditions to include mumps, alcoholism, carcinoma, renal diseases, abdominal trauma and other abdominal disorders, blockages, or diseases. Because the pancreas is sensitive to proximal abdominal disorders the specificity of the lipase test for pancreatitis is reduced.
384
3. If left untreated, what is likely to occur when pancreatic secretions are blocked from reaching the duodenum?
In chronic pancreatitis the pancreatic secretions are blocked and from reaching the duodenum and begin to digest the pancreas itself, a condition called autodigestion.
385
4. What can cause difficulty with turbidimetric methods for lipase?
They are subject to analytical imprecision due to unstable substrates as well as false elevations due to interference from rheumatoid factor.
386
1. Where is myoglobin found in the body?
Myoglobin is found in all muscle types (smooth, skeletal, and cardiac).
387
2. What is the function of myoglobin?
Myoglobin’s function is to transport oxygen within muscle cells.
388
3. Describe the actions of myoglobin following an MI.
The first analyte to rise above normal levels following a MI is myoglobin. Myoglobin rises earlier than creatine kinase. Initially within the first hour following an infarct it will rise dramatically and peak between four to twelve hours following the infarct and return to normal levels within 18 hours.
389
4. Why does cardiac troponin have specificity?
Specificity for cardiac troponin exists because it has a differing amino acid sequence from skeletal troponin.
390
5. Following an MI, what happens to troponin levels?
Troponin levels rise rapidly within the first few hours (<6) following a MI and remain elevated longer than all other associated analytes and enzymes used to measure MI.
391
1. What determines the nature of proteins?
The sequence and individual characteristics of amino acids.
392
2. What is the difference between simple and conjugated proteins? Give examples of each.
Simple proteins are those that contain only amino acids or their derivatives. Conjugated proteins are those containing an additional non-protein component, called a prosthetic group. Albumin and globulin are examples of simple proteins. Nucleoproteins, mucoproteins, chromoproteins, phosphoproteins, and lipoproteins are examples of conjugated proteins.
393
3. What is meant by the expression proteins behave as colloids?
Colloids are particles that stay suspended in a medium and do not settle out. Proteins are held in solution due to an attraction between the water molecules and the protein molecules, making them behave as colloids.
394
4. What determines the electrical charge of proteins?
The pH of the solution that the protein is in.
395
5. What are acute phase reactants? Give an example.
They are proteins that are useful as markers for tissue damage and inflammation. CRP is one of the most sensitive acute phase reactants.
396
6. Where is C-reactive protein (CRP) synthesized and what are some of its functions?
CRP is synthesized by the liver and bonds to the polysaccharides found in many bacteria, fungi, and parasites. CRP can help initiate phagocytosis and the lysis of invading cells. CRP recognizes and binds with endotoxins released by bacteria and detoxifies or eliminates these toxins from the blood.
397
7. What are some of the roles of serum complement?
These proteins facilitate the body’s immunologic and inflammatory responses. It increases vascular permeability, allowing antibodies and white blood cells to be delivered to the area of inflammation. It also acts to increase chemotaxis, phagocytosis of invading substances, and the response of antibody to antigens.
398
8. What are two functions of immunoglobulins?
To recognize antigens and initiate a response for the destruction or neutralization of the antigens.
399
9. Which of the immunoglobulins are found in normal patient serum and which additional ones are found in patients with multiple myeloma?
IgG, IgA, and IgM are found in normal patient serum. IgD and IgE are found in the serum of patients with multiple myeloma.
400
1. What percentage of total protein is made up of albumin, where is albumin formed, and what are some of the functions of albumin?
About 60 percent of total serum protein is made up of albumin. Albumin is formed in the liver and is responsible for maintaining colloidal osmotic pressure and transporting blood constituents such as drugs, hormones, and lipids.
401
2. Where are globulins synthesized and what are their functions?
Globulins are either synthesized in the liver or the mononuclear phagocytic system. Globulins are the key building blocks of antibodies, and they play a lesser role in osmotic pressure and transport.
402
3. Why might a patient with chronic liver disease have a decreased albumin but increased globulin level?
The patient’s liver cannot produce proper amounts of albumin. So their mononuclear phagocytic system produces greater amounts of globulins to maintain a normal total serum protein level.
403
4. Proteins are broken down into amino acids by the action of what intestinal enzymes?
Trypsin, chymotrypsin, and peptidases.
404
5. Why does albumin have such a vast capacity for binding and transporting substances?
Albumin is an anion at a pH of 7.4 and has over 200 negative charges per molecule. Because of all these charges, albumin has a vast capacity for binding with other substances and transporting them throughout the body.
405
6. When total protein is broken down by electrophoresis, how many globulins will become evident, and what are they called?
There will be five fractions, four of which are globulin bands. The four globulin bands are: alpha one globulin, alpha two globulin, beta globulin, and gamma globulin.
406
7. What are some of the proteins that fall into the various globulin fractions?
Glycoproteins and lipoproteins are seen in the α1-globulin fraction. The α2-globulin fraction contains α2- lipoproteins, haptoglobin and ceruloplasmin. The β-globulin fraction contains the β-lipoproteins, fibrinogen, and transferrin. The γ-globulin fraction contains the immunoglobulins.
407
8. What two conditions generally cause a change in a patient’s total serum protein level?
. Either from a change in the plasma water volume level or a change in the concentration of one or more of plasma proteins.
408
9. Define hyperproteinemia, hemodilution, and hypoproteinemia.
Hyperproteinemia: an increased protein level caused by decreased plasma water volume. Hemodilution: too much plasma water. Hypoproteinemia: decrease in the total serum protein level.
409
10. What is the diagnostic significance of hyperalbuminemia?
It is of no diagnostic significance with the exception of dehydration.
410
11. What conditions can produce hypoalbuminemia?
Impaired protein synthesis as a result of liver disease or decreased protein intake. Increased catabolism as a result of inflammation or tissue damage. Malabsorption syndromes or malnutrition resulting in the reduced absorption of amino acids. Protein loss due to conditions such as renal problems, diabetes, or severe burns.
411
12. What are the causes of increased or decreased serum globulin levels?
Globulins are usually decreased in cases of malnutrition or immunologic deficiencies and increased by immunologic malignancies such as multiple myeloma.
412
13. If frozen serum is used for total protein analysis, how should the sample be handled?
The sample should be thawed and well mixed prior to testing.
413
14. Explain the principle of the biuret method of total serum protein analysis.
Copper ions react in an alkaline solution with the peptide linkages of proteins to form a violet-colored complex. The intensity of the color produced is proportional to the amount of protein present.
414
15. Explain how refractometers measure total serum protein.
Many refractometers have a calibrated scale that gives a direct readout of total serum protein concentration. This instrument measures the total solids dissolved in the serum.
415
16. Explain the principles of the dye-binding methods for albumin analysis.
In the dye binding methods, bromcresol green or bromcresol purple are widely used. These dyes have a higher affinity for albumin than for the other protein fractions so they bind primarily with albumin in the sample. The absorption of the dye-albumin complex is determined spectrophotometrically at 628 nm for bromcresol green and at 603 nm for bromcresol purple.
416
17. How is an albumin/globulin (A/G) ratio determined and what is the normal range?
The albumin level is subtracted from the total serum protein value to determine an estimate of the total globulin concentration. The albumin level is then compared to the globulin level and expressed as a ratio. The normal A/G ratio is >1.0:1.
417
1. Why are protein levels in CSF lower than that of serum, and why do some diseases allow proteins to leak into the CSF?
Because protein molecules are large and do not cross the blood-brain barrier. Some disease processes alter the permeability of this protective membrane and allow proteins to leak in.
418
2. Where does most of the protein found in CSF come from, and what can be said about its concentration in the spinal cord?
From plasma that is ultrafiltered through the walls of the meninges and choroid plexuses. Protein levels increase as CSF works its way down the spinal cord, with the highest levels found in the lumbar spine.
419
3. Why do CSF protein levels increase when there is a tumor obstructing the spinal cord?
The tumors impedes the flow of CSF and the CSF in the lumbar spine becomes stagnant. Proteins equilibrate across the walls of the meningeal capillaries into the CSF raising protein levels.
420
4. What other conditions can cause increased CSF protein?
When lesions inflame the meninges, when there is a cerebral hemorrhage, or in cases of neurosyphillis. Also occurs in patients with multiple sclerosis or other demyelinating diseases.
421
5. Why should repeated spinal punctures and bloody tap specimens be avoided?
Repeated punctures should be avoided because total protein levels may be increased due to the trauma of the previous punctures and not be truly indicative of the patient’s condition. Total protein content, even in a clear supernatant of a bloody specimen, will reflect the contamination of blood proteins.
422
6. Once testing is completed, what is done with the leftover CSF sample?
They should be stored refrigerated for up to 2 weeks in the event other testing may be required.
423
7. Why are dye-binding methods for CSF protein analysis preferred over turbidimetric methods?
Because they require as little as .025 ml of sample, while turbidimetric methods can require as much as 0.5 ml of sample.
424
8. Explain the principle of turbidimetric testing for CSF protein and list sources of test interference.
Sulfosalicylic acid and sodium sulfate reagent produces a fine suspension of protein when added to CSF. The protein concentration is proportional to the turbidity produced. Turbidity is measured as a decrease in light transmittance at 620 nm. Interference from hemoglobin or drugs that precipitate protein can affect results.
425
9. Why are CSF specimens, from patients with multiple sclerosis or demyelinating diseases, fractionated by electrophoresis?
Patients with these diseases may or may not show an obvious elevation in CSF protein; these conditions are more easily detected using electrophoresis. In normal CSF samples, the γ-globulin is less than 11% of the total protein, but in multiple sclerosis its level increases to more than 18%.
426
1. What are the classes of lipids most important to laboratory technicians?
They are fatty acids, triglycerides, phospholipids, plant sterols, sphingolipids, and cholesterol.
427
2. What is unique about the unsaturated fatty acids derived from plant seed or fish oils?
They contain many of the essential fatty acids that humans require but cannot synthesize.
428
3. How does the energy produced from fatty acid metabolism compare to the energy produced from the metabolism of carbohydrates?
Unit for unit, the amount of energy produced by metabolizing a fatty acid is twice that of metabolizing a carbohydrate.
429
4. Triglycerides make up what percentage of the stored body fats?
About 90 to 95%.
430
5. Why are phospholipids essential components of cell membranes?
Because of their ability to align themselves between water and lipid phases. Providing the lipid portion of the cell membrane.
431
6. Why are sterols derived from plant sources used for patients with increased cholesterol levels?
When ingested, they help to inhibit the absorption of cholesterol. Plant sterols are used to treat patients with elevated levels of plasma cholesterol.
432
7. Sphingolipids are essential parts of which cellular membranes?
Particularly those of red blood cells and central nervous system cells.
433
8. Cholesterol is acquired from what sources?
8. Some from the diet, but the majority is synthesized by the liver.
434
1. LDL and HDL serve what functions in the transport of cholesterol?
LDL transports cholesterol to the tissues, and HDL transports cholesterol away from tissues to the liver.
435
2. What are the conditions that can cause increased cholesterol levels?
Increases occur during pregnancy, uncontrolled diabetes mellitus, hypothyroidism, and biliary cirrhosis.
436
An outpatient’s cholesterol level was 200 mg/dl 2 weeks ago, and it is now 180 mg/dl. Aside from medications or dietary changes, what could account for this difference?
It could be due to inpatient status; they are now in a reclining position. Cholesterol levels can decrease by as much as 10 percent when a patient goes from an erect to reclining position.
437
4. If an EDTA plasma sample is used for cholesterol analysis, what correction must be made to the results?
EDTA samples must be corrected so that results are converted to serum values. This is done by multiplying the EDTA value by a factor of 1.03.
438
H2O2 serves what function during enzymatic cholesterol analysis?
To react with phenol and 4-aminophenazone in the presence of peroxidase to form ο-quinoneimine dye. The intensity of the color that is formed is proportional to the cholesterol concentration in the sample.
439
6. To what upper limits are results linear during enzymatic cholesterol analysis? And, what must be done to the sample prior to retesting?
Upper limits are usually about 500 mg/dl. The sample must be diluted 1:1 with normal saline before retesting.
440
7. Why is it important to perform HDL cholesterol testing as soon as possible after specimen collection?
While HDL is stable for up to 4 days at 4°C, significant changes in the levels will occur by the 7th day following collection.
441
8. Why is HDL is sometimes called the good cholesterol?
HDL carries cholesterol from tissues to the liver for conversion to bile salts, while LDL carries cholesterol to the tissues for deposit (this includes the deposit in the blood vessels). HDL competes with LDL for binding sites on the tissue receptors and, in doing so, reduces the cholesterol accumulation in the blood vessels, which reduces cardiovascular risk.
442
9. Magnesium and dextran sulfate serve what function during HDL analysis?.
When magnesium and dextran sulfate are added to a sample, the larger, lipid-rich chylomicrons, VLDL and LDL, are precipitated selectively, leaving behind the HDL.
443
10. What is a desirable LDL:HDL ratio?
A ratio of less than 3:1 (LDL:HDL).
444
11. What formula is used to calculate LDL cholesterol?
LDL = Total cholesterol − [HDL cholesterol + (Triglycerides ÷ 5)]
445
Using the formula from the above question, calculate the LDL level for the patient with the following results: total cholesterol = 180 mg/dl, HDL cholesterol = 40 mg/dl, and triglyceride = 250 mg/dl.
(250÷5)=50 [40 + 50] = 90 180 − 90 = 90
| LDL = 90 mg/dl
446
13. What is the importance of having accurate total cholesterol, HDL cholesterol, and triglyceride values when calculating LDL levels?
LDL determinations are based on a calculation involving total cholesterol, HDL cholesterol, and
triglyceride. An error in any of these values would also create an error in determining the LDL concentration.
447
14. When would LDL concentrations not be calculated?
If the patient’s triglyceride level is above 400 mg/dl. The formula is not accurate if triglycerides are above this level.
448
1. What is the primary purpose of triglycerides and of what are they made of?
To act as a storage source for energy in the body. They are made up of 3 molecules of fatty acids bound to 1 molecule of glycerol.
449
2. Why must cells that synthesize triglycerides contain glucose?
The cells that synthesize triglycerides do so by converting fatty acids into triglycerides by esterification with glycerol–3-phosphate, a compound that is a product of glucose metabolism. Because of this required product of glucose metabolism, cells must contain glucose in order to have the ability to form triglycerides.
450
3. What is insulin’s effect on triglycerides levels?
Insulin promotes the formation of triglycerides by the adipose tissues and a decreased amount of insulin increases the hydrolysis of triglycerides.
451
4. How do the roles of chylomicrons and VLDL differ in the transport of triglycerides?
Chylomicrons transport triglycerides from dietary sources in the intestines to the tissues, and VLDL transports the triglycerides that have been synthesized in the liver to the tissues.
452
5. Triglyceride testing is primarily used to diagnose what condition?
Cardiovascular risk.
453
6. Why are enzymatic methods of triglyceride testing more commonly used?
They do not require purification or extraction steps and are easily automated.
454
7. Why are patients instructed to fast for at least 12 hours prior to sample collection for triglyceride testing?
Triglyceride levels are quickly affected by food in-take. If the patient has not been fasting for at least 12 hours before collection, the triglyceride results will be falsely elevated.
455
8. Describe the principle of enzymatic triglyceride testing.
The triglycerides are hydrolyzed by microbial lipase to produce glycerol and free fatty acids. The glycerol is then put through several other coupled enzymatic reactions with the last product formed being a red quinoneimine dye. The absorbance of the dye is read at 510 nm and is proportional to the triglyceride concentration.
456
9. What are the sources of error in enzymatic triglyceride testing?
Sources of error include the use of stoppers that have been lubricated with glycerol and not monitoring the stability of the reagents.
457
1. Briefly define the three categories of hormone functions.
(1)
Regulatory function is concerned with maintaining the chemical composition of extracellular and intracellular fluids.
(2) Hormones play an important role in your growth and development, which is what morphogenesis is.
(3) Integrative action is when two or more hormones work together to achieve the desired outcome.
458
2. On what is the synthesis of hormones based?
Based on the circulating levels of each hormone and the body’s need for them.
459
3. How is the cerebral cortex, or neural center, stimulated to initiate the production and secretion of hormones?
By thoughts, emotions, stress, and circadian rhythms.
460
4. Give an example showing how a substance’s change in plasma concentration can cause a hormonal response.
For example, parathyroid hormone is secreted when plasma concentrations of calcium are low or insulin is secreted when plasma glucose levels are high.
461
5. When you develop a feeling of sudden fear or anxiety, how may your neural centers react?
The neural centers in the brain transmit a message by the sympathetic nervous system to the adrenal medulla that results in the secretion of epinephrine.
462
6. Define target in relationship to hormone responses.
The term target is used to describe a receptor site for any hormone.
463
7. What are the three characteristics of the hormone-receptor complexes?
They are highly specific. The complexes have a saturation point. They have a high affinity.
464
8. Why do many obese patients have increased insulin levels?
The target cell receptor response in an obese patient can be decreased. Obese patients often have a chronically elevated level of the hormone insulin. This increased level causes the cells’ decreased sensitivity and response to insulin.
465
9. What is specificity spillover?
Some hormones have a very strong affinity for their own receptor sites and some affinity for the receptor sites for another hormone. This effect is known as specificity spillover. This effect normally occurs between hormones with similar structures.
466
10. What are the causes of receptor site dysfunction?
Receptor site dysfunctions may occur due to a variety of acquired or congenital endocrine diseases. These disorders may be due to a lack in the number of receptor sites, an interference with the receptor binding (such as the presence of an anti-receptor antibody), a structural abnormality in the receptor site, or a defect in the chemical processes that occur after the receptor binding takes place.
467
1. How does iodine become bound to the thyroidal protein, thyroglobulin?
The iodine from food, in the form of iodides, is transported to the follicular cells of the thyroid gland where the iodides are concentrated. Iodide is oxidized in the thyroid gland and bound to the tyrosine molecules in a thyroidal protein called thyroglobulin.
468
2. How are T3 and T4 formed?
Once the signal is received for thyroglobulin to be released, the thyroglobulin is acted upon by the enzyme tyrosine iodinase, forming free monoiodotyrosine (MIT) and diiodotyrosine (DIT). Two DIT molecules will condense to form tetraiodothyronine (T4), and one MIT molecule plus one DIT molecule will condense to form triiodothyronine (T3).
469
3. What are the roles TSH plays in synthesis of thyroid hormones?
Each step in the synthesis of thyroid hormones is regulated by the pituitary hormone TSH (thyroid stimulating hormone). This hormone stimulates the concentration of iodides, thyroglobulin synthesis, and the synthesis of T3 and T4 by follicular cells. The breakdown rate of thyroglobulin to release T3 and T4 is also controlled by TSH.
470
4. Which of the thyroid hormones is secreted in the largest amount and which is more potent?
T4 is the hormone secreted in the larger amount. T3, although in an amount less than half that of T4, is 4–5 times more potent. Most of the total metabolic effect of thyroid hormones is attributed to T3.
471
5. Which forms of the thyroid hormones are capable of attaching to cell surfaces?
Free T3 and T4.
472
6. What are the characteristics of hyperthyroidism and hypothyroidism?
Hyperthyroidism is an increased activity of the thyroid gland. It is characterized by nervousness, heart palpitations, restlessness, and insomnia. Hyperthyroidism can be accompanied by an enlarged thyroid (called a goiter). Hypothyroidism is a decrease in thyroid activity and is characterized by drowsiness, fatigue, and lethargy. Marked hypothyroidism can cause weight gain, coarsened features, and thick, scaly skin.
473
7. What causes primary hypothyroidism and how does it effect TSH levels?
It is caused by a defect in the thyroid gland itself. TSH levels are increased.
474
8. What causes secondary hypothyroidism and how does it effect TSH levels?
It is caused by a defect in the anterior pituitary gland or the hypothalamus. TSH level can be low, within normal limits or slightly elevated.
475
9. What is the cause of congenital hypothyroidism?
It is due to the absence of the thyroid gland itself or a defect in the synthesis of the thyroid hormones.
476
10. What effect does hyperthyroidism have on TSH and T4 levels?
TSH levels are low and free T4 levels are elevated.
477
11. Why are non-isotopic immunologic methods for thyroid hormone testing so popular?
Because they are safer (no radioactive waste) and do not require the special licenses or training that radioimmunoassay methods require. In addition, non-isotopic methods are easily automated.
478
12. What special considerations must be taken when using plasma for thyroid hormone analysis?
The sample can develop fibrin clots after freezing and thawing, and the fibrin clots can interfere with automated testing.
479
13. Define specimen collection requirements for neonate T3 analysis.
Either capillary tubes or filter paper can be used. Dried blood samples are stable and easily transported. T3 neonate testing is performed to screen for congenital hypothyroidism, and the sample should be collected 3 to 7 days after birth. You should avoid touching the filter paper (collection area) or exposing it to extreme heat of light.
480
14. What are the enzyme labels and substrates used to determine enzyme activity while performing T3 testing?
Enzymes used in T3 assays may include peroxidase and alkaline phosphatase. The substrates used may be either fluorescent or chemiluminescent to determine activity.
481
15. T4 testing methods require the separation of free and bound T4. Briefly explain two methods of separation.
Some enzymatic methods use plastic beads to immobilize the T4 antibody. The bound and free analyte are then separated by decanting and washing the beads. Other methods use ferromagnetic particles and the free and bound T4 are separated magnetically.
482
. For TSH analysis, why are enzymatic immunometric methods gaining in popularity?
In addition to the safety and other considerations regarding radioimmunoassays, enzymatic immunometric assay methods are gaining in popularity because they are more sensitive and faster than the radioactive methods.
483
(1) These hormones include growth hormone, prolactin, and TSH.
Anterior pituitary hormones.
484
(2) This hormone can cause dwarfism and giantism.
Growth hormone.
485
(3) This hormone stimulates initial release of milk from
| the mammary glands.
Oxytocin.
486
(4) These hormones induce the growth of gonads and the
| secretion of gonadal hormones.
Gonadotropins.
487
```
(5) Anti-diuretic hormone and oxytocin fall into this class
of hormones.
```
Posterior pituitary hormones.
488
(6) These hormones are formed by glands located above
| each kidney.
Adrenocortical hormones., Adrenomedullary hormones.
489
(7) Catecholamines is the term used to collectively
| describe these hormones.
Adrenomedullary hormones.
490
(8) This hormone regulates both calcium and phosphorus
| homeostasis.
Parathyroid hormone.
491
(9) These hormones include insulin and glucagon.
Pancreatic hormones.
492
10)
| Food in the gut stimulates the releases of these hormones.
Hormones of the gastrointestinal
| tract.
493
(11) This hormone prepares the uterus for implantation of a fertilized ovum.
Progesterone.
494
(12) This hormone is greatly increased in women with a choriocarcinoma.
Human chorionic gonadotropin.
495
(13) Found in increased amounts in men suffering from testicular cancer.
Human chorionic gonadotropin.
496
(14) Male sex hormone and also seen in women with adrenal or ovarian tumors.
Testosterone.
497
1. Define therapeutic drug monitoring (TDM).
The tracking of a patient’s drug concentration.
498
2. What are some of the factors that must be taken into account when monitoring a drug’s level in the blood?
Absorption rate of the drug into the blood, distribution of the drug within the body tissues, metabolism of the drug by body tissues, and excretion of the drug. Additional factors include the patient’s height, weight, sex, and age.
499
3. Define bioavailability and first-pass effect.
Bioavailability is the amount of drug that eventually makes its way into systemic circulation. The first-pass effect describes the effect of the liver on drugs that have been absorbed and metabolized, thus decreasing their bioavailability.
500
4. What is drug distribution?
Drug distribution is the process of getting the drug from the blood into the cells of the targeted organ.
501
5. Drug metabolism, or biotransformation, occurs in what organ and what happens to the drug during this process?
The liver transforms drugs into water-soluble substances.
502
6. What happens to a geriatric patient’s ability to metabolize drugs?
The metabolism pattern can slow down considerably, and the drug that they have taken for years, with no ill effects, may have to be reduced in dosage.
503
7. Define drug half-life.
A half-life is the amount of time it takes for the body to reduce the blood concentration level of a drug by 50 percent.
504
8. Define peak and trough.
A peak level is drawn when the drug reaches its maximum absorption or concentration. A trough level is drawn just before a dose is administered.
505
9. Define steady state.
The steady state of a drug occurs when there is an average constant level between the peaks and troughs.
506
10. When are peak samples collected for oral, intramuscular, and intravenous drugs?
Orally, will range from 1 to 5 hours after ingestion; intramuscular, collection should occur about 60 minutes after the injection; and intravenous, 30 minutes after the infusion has stopped.
507
(1) This drug restores the force of cardiac contractions.
Digoxin.
508
(2) This drug accumulates in cardiac tissues at levels 15 to 30 times that of plasma.
Digoxin.
509
(3) Peak concentrations for this drug should be drawn after equilibration
between tissue and plasma levels.
Digoxin.
510
(4) This anticonvulsant is used to treat epilepsy.
Phenytoin.
511
(5) For this drug, peak samples are drawn to check for toxicity and trough samples are collected to check for therapy adequacy.
Phenytoin.
512
(6) This drug is an antibiotic used to treat severe infections.
Gentamicin.
513
(7) This drug is closely monitored because it adversely effects the
patient’s kidneys and hearing.
Gentamicin.
514
(8) Its primary use is for the treatment of asthma.
Theophylline.
515
(9) If allowed to reach toxic levels, this drug can cause death rates as
high as 50%.
Theophylline.
516
(10) This drug acts on neurotransmitters and has a sedating effect on the
central nervous system.
Lithium.
517
(11) Ion-selective electrode methods are used to measure levels of this
drug.
Lithium.
518
1. How do non-drinkers and heavy drinkers differ regarding their tolerance and metabolism of ethanol?
A heavy drinker will have a greater tolerance for the effects of the alcohol. A non-drinker will metabolize about 15 to 18 mg/dl per hour while a heavy drinker will metabolize about 30 mg/dl per hour.
519
2. In what products do you find methanol, and what problems can it cause if ingested?
It is found in cleaning solutions, antifreeze, and canned fuels. It is sometimes consumed intentionally by alcoholics as an ethanol substitute or accidentally by children. If ingested, methanol can cause blindness or death.
520
3. Compare isopropanol to methanol and ethanol.
Isopropanol is not quite as toxic as methanol, but it has twice the central nervous system depressant action as ethanol.
521
4. What is the meaning of the term sobriety?
Sobriety is the term used to describe the clinical opinion of an individual’s state of intoxication.
522
5. If you are required to testify in court, what will you, as the laboratory technician, be defending?
The manner in which the testing was accomplished.
523
6. You are preparing to collect a legal blood alcohol specimen, and the patient is combative and refuses to consent. Under what conditions can you collect their blood despite their objections?
You should never attempt to draw the blood of someone who has not consented to the procedure unless told to do so by a competent authority. In most cases, the competent authority will be the base commander. This person will direct the collection of the sample after being advised by the Staff Judge Advocate.
524
7. Briefly explain any special conditions used to clean the phlebotomy site before collection of a sample for alcohol testing.
Do not use alcohol as a skin-cleansing agent. Use an aqueous iodine solution or Merthiolate before performing the venipuncture.
525
8. Describe one way to secure a blood alcohol sample and explain what is meant by chain of custody.
One way is to use a special locked box in the refrigerator. The chain of custody is the tracking system used to determine who had access to the sample from the time it was collected to the time the result was released to the proper authority.
526
9. What happens when you expose an ethanol sample to room air?
It will decrease the ethanol level of the sample and cause inaccurate results.
527
10. An emergency room provider has ordered a blood alcohol test on a child who has swallowed a bottle of rubbing alcohol, and your lab only performs the enzymatic test for ethanol. What type of results can you expect and what should you recommend to the provider?
The results will appear very low. You should recommend testing the specimen by gas chromatography because this methods can distinguish between the various types of alcohols.
528
1. What are two common, over-the-counter drugs frequently ingested accidentally by children or taken by adults in suicide attempts?
Acetaminophen (Tylenol) and salicylate (aspirin).
529
2. What could be the results of taking massive amounts of acetaminophen and what are the initial clinical findings of a person who has?
It can cause severe liver damage or even death. The initial clinical findings are not a very good indication of the degree of hepatic damage because the findings are so mild.
530
3. When is the full extent of hepatic damage evident following an acetaminophen overdose?
It will become evident 3 to 5 days after the ingestion of acetaminophen.
531
4. When are blood samples for a suspected acetaminophen overdose collected if the time of ingestion is known? What if the time of ingestion is unknown?
The samples should not be drawn any earlier than 4 hours after ingestion. If the time of ingestion is unknown, then samples should be taken at 2- to 3-hour intervals to see if levels are climbing or declining.
532
5. What is the effectiveness of the antidote (N-acetylcysteine) for acetaminophen overdose?
The sooner the antidote is administered, the more efficient it is. Maximum efficiency is seen if the antidote is administered within 8 hours of ingestion, but it declines sharply if given between 18 and 24 hours after ingestion.
533
6. Why are immunoassay methods normally used for acetaminophen analysis rather than chromatography methods?
Because they are rapid, easily performed, and very accurate.
534
7. What analyte is tested for in an aspirin overdose?
Salicylate.
535
8. Briefly discuss the half-life of aspirin and its metabolite salicylate.
Once ingested, the half-life of aspirin is about 15 minutes, at which time it is converted to salicylate. At high therapeutic or toxic levels, the half-life of salicylate is prolonged: 15 to 30 hours at high levels versus 2 to 3 hours for low doses.
536
9. What happens to the patient during an aspirin overdose?
Overdoses of salicylate initially cause hyperventilation because the respiratory center of the brain is stimulated. Prolonged hyperventilation can first lead to respiratory alkalosis, this later changes to a metabolic acidosis. In severe cases coma and seizures can result.
537
10. How do slow-release forms of aspirin affect salicylate analysis, and what is done to counteract this effect?
Consideration must be given to when peak absorption has taken place. Slow release formulas can delay the peak absorption of the drug. If sample collection begins before 6 hours post-ingestion, sample collection should continue every 2 to 3 hours to ensure absorption is complete.
538
11. What purpose does the treatment for salicylate intoxication serve and what forms of treatment are used?
Treatment is aimed at preventing further absorption of the drug. Syrup of ipecac or activated charcoal can be used. Sodium bicarbonate is given to the patient to prevent metabolic acidosis.
539
1. What is the difference between local and remote effects of poisons?
A local effect means that there is a direct action at the point where the poison is applied. A remote effect is caused when the action of the poison takes place at a site away from the site of application.
540
2. Define acute poisoning and chronic poisoning.
Acute poisoning is a condition brought on by a single dose of the poison. Chronic poisoning is a condition brought on by repeated exposure over a period of time.
541
3. How is carbon monoxide produced and describe its interaction with hemoglobin?
It is a by-product of burning fossil fuels. Common sources of carbon monoxide are cigarettes, gasoline engines, and improperly ventilated heating system. When inhaled, carbon monoxide combines tightly with hemoglobin to form carboxyhemoglobin. This action displaces any oxygen that may bind with hemoglobin because carbon monoxide has an affinity for hemoglobin that is about 250 times greater than that of oxygen.
542
4. What are the primary effects of carbon monoxide exposure and which organs are most sensitive to the effects?
The primary effect is hypoxia. Organs with a high demand for oxygen, such as the brain and the heart, are the most sensitive to hypoxia.
543
5. Describe the treatment for carbon monoxide poisoning and its half-life under room air and pure oxygen conditions.
Treatment for carbon monoxide poisoning involves removing the individual from the contaminated area and administering oxygen. The half life of carbon monoxide is 5 to 6 hours if the patient is breathing room air, but it is only 11/2 hours if breathing pure oxygen.
544
6. How could people be exposed to heavy metals in their homes?
The ingestion of lead-based paint chips and improper use of insecticides containing heavy metals.
545
7. What methods are used to perform heavy metal analysis?
Atomic absorption spectrophotometry and mass spectrophotometry.
546
8. Briefly explain why the Air Force maintains a drug urinalysis testing program and what involvement the laboratory has with the program.
It is used as a screening tool and a deterrent to illegal drug use. The laboratory may play a role in the collection and shipment of specimens. Our amount of involvement is usually dictated by the base commander.
547
9. Why do amphetamines have a high potential for abuse?
Because they produce a feeling of euphoria, a feeling of well-being and self-esteem, and heightened mental and physical capacity.
548
10. What effect do barbiturates have on the patient and for what are they prescribed?
They suppress the central nervous system and have a sedating and hypnotic effect on the individual. They are often prescribed as an anticonvulsant drug and are also to treat intracranial pressure due to head trauma or injury.
549
11. How is tetrahydrocannabinol (THC) most often administered?
THC is most often administered by smoking marijuana or hashish.
550
12. What is the difference between the coca plant and the cocoa plant?
The coca plant is used to make the drug cocaine. The cocoa plant is used to make chocolate.
551
13. What are some effects of cocaine use and what can occur in an overdose?
The effects include increased blood pressure and heart rate, as well as increased body temperature. Overdoses produce seizures, arrhythmias, and myocardial infarction. Sudden death due to cardiotoxicity can occur.
552
14. What opiate is preferred by illegal drug users and how is it administered?
Heroin is the preferred opiate by illegal drug users. It is generally administered by intravenous injection.
553
15. How can someone who has not taken opiates still have morphine or codeine in their urine?
The consumption of poppy seeds in baked goods, such as cakes, muffins, and bread rolls, can lead to urinary excretion of morphine and codeine.
554
16. What was the original use of phencyclidine and why is it popular for illegal use?
As a surgical anesthetic. The euphoric and hallucinogenic properties of this drug make it popular for illegal use.
555
1. The clonal theory of carcinogenesis (the production of a cancer or carcinoma) states that cancers derive from what type of cell?
A transformed cell.
556
2. List the clues that have led scientists to believe that one or more genes must be altered before a malignant cell is formed.
First, the relationship between cancer and the age of the patient is empirical, second, cancer cells can be shown to have multiple genetic lesions, and thirdly, cancer is more likely to occur in cells that proliferate.
557
3. List the stages of the genetic process that causes a patient’s cells to go from healthy to that of cancerous.
Stage One – the initial DNA damage to the cell.
Stage Two – the chromosome breakdown and rearrangement, and then gene replication. Stage Three – the selection of successful growing mutant cells.
558
4. In stage one of the genetic process, what causes the initial DNA damage to the cell?
The DNA damage can be caused by a variety of carcinogens, such as radiation, chemicals, viruses, or unknown agents.
559
5. What are oncogenes?
They are newly expressed, or suppressed, genes that have been created as a result of the DNA changes to the cell.
560
6. Name the first tumor marker and the disease it is associated with.
Bence Jones protein and multiple myeloma.
561
7. Why has the measurement of serological tumor markers become a common means for the detection and diagnosis of neoplastic disease?
Because the blood levels of serum tumor markers usually reflect the changes in the tumor’s size and activity. They also aid in monitoring the patients course of treatment.
562
8. Where are tumor markers found and what type of substances are they?
Tumor markers are not only found in the blood, they can be found in all body fluids including urine, CSF, and effusions (exudates and transudates). Tumor markers are represented in small and large molecules, such as peptides, proteins, glycoproteins, enzymes, hormones, immunoglobulins, and mucins.
563
9. What four roles do laboratory tests serve the cancer patient and their providers?
The roles are the detection or screening of the cancer, the confirmation of the condition, the classification or staging of the condition, and the monitoring of the condition.
564
10. Define diagnostic sensitivity.
The diagnostic sensitivity of a test is defined as the probability of obtaining a positive result for a patient with a given disease, that is, the percentage of individuals with a disease who will be positive.
565
11. Define diagnostic specificity.
The diagnostic specificity of a test defines the probability of obtaining a negative result for a patient without the disease, that is, the percentage of people without the disease who test negative.
566
12. When a “stepwise” screening policy for cancer is used, which patients receive further testing?
When using a stepwise screening policy, only the patients with positive results at the first screening are later put through more diagnostic testing.
567
13. What is the general rule to use to increase the efficiency of cancer screening when combining two screening tests.
Generally, it is more efficient screening to combine two tests that are complimentary (that is, are directed at different anatomical or biochemical features of the tumor) than to combine tests that are directed at the same type of features. An example of complimentary testing would be the combined use of a sputum cytological examination and a chest X-ray examination for the screening of lung cancer.
568
14. What is meant by the requirement that confirmatory tests for cancer diagnosis must be above a certain “decision level?”
Laboratory tests for the confirmation of a cancer diagnosis should have a 100% diagnostic specificity – there should be no false positive results.
569
15. Tumor classification is used to describe the degree of tumor differentiation. List the terms used to describe tumor differentiation.
Tumors are classified as: well differentiated, moderately well differentiated, or poorly differentiated. Poorly differentiated tumors are generally more aggressive and have a poorer prognosis.
570
16. What is the threefold purpose of the staging system for tumors?
It gives a reasonable estimate of: (1) the patient prognosis (that is, recurrence of the cancer), (2) the patients possible response to therapy, and (3) the most likely course their disease will take.
571
17. When monitoring a patient with an established prostate cancer, what would an increased PSA value signal the provider to do?
It would signal the provider to explore the patient surgically again to remove the additional cancer cells or to change the course of their chemotherapy.
572
18. What suggested criteria should the ideal tumor marker possess?
It should: be easy and inexpensive to measure in readily available body fluids, be specific to the tumor studied and commonly associated with it, have a direct relation between the fluid level (i.e. plasma) of the marker and the size of the tumor mass, have an abnormal plasma level, urine level or both in the presence of micrometastases, have plasma levels, urine levels, or both, that are stable and not subject to wild fluctuations, and if present in the plasma of healthy individuals, exists at a much lower concentration than that found in association with any and all stages of the cancer.
573
19. What three benchmarks can be used to evaluate the tumor markers we have available to us now?
The three benchmarks are: (1) that the marker should predict a higher or lower risk for eventual development of recurrence, (2) that the marker should change as the current status of the tumor changes over time, and (3) that the marker should precede and predict recurrence before it is clinically detectable.
