Chemistry 51-70 :) Flashcards
1
Q
Name 3 substances that are increased in the blood with renal disease.
A
BUN, Creatinine, and Uric Acid
2
Q
What is urea?
A
Byproduct of protein metabolism
3
Q
Why should tubes containing fluoride or citrate not be used when collecting blood for urea if analysis will be by the urease method?
A
Fluoride and citrate inhibit urease.
4
Q
Where is 98% of the body’s creatinine located?
A
In the muscles
5
Q
What reaction is used to measure creatinine?
A
Jaffee Method
6
Q
What is the significance of the BUN:creatinine ratio?
A
It helps to determine the cause of increased BUN
7
Q
What non-protein nitrogen doesn’t change easily?
A
Creatinine because its related to muscle mass and is not affected by diet
8
Q
What is uric acid?
A
Byproduct of purine catabolism
9
Q
What reagent is commonly used to measure uric acid?
A
Uricase
10
Q
What may result from high levels of uric acid?
A
Urate crystals may precipitate in joints and tissue
11
Q
Why must the pH of urine for uric acid determination be adjusted to 7.5-8?
A
To prevent precipitation of uric acid because it precipitates at acid pH.
12
Q
Where is ammonia formed?
A
Mainly in the intestines from deamination of amino acids and is converted to urea by liver
13
Q
When is ammonia elevated?
A
Hepatic failure and Reyes syndrome
14
Q
What is Reye’s syndrome?
A
An acute, fatal degeneration of the liver usually in children with viruses and aspirin use.
15
Q
What are 2 technical difficulties in performing ammonia determination?
A
Levels increased rapidly after drawing and need to be put on ice immediately and plasma separated from cells. Also can be contaminated from detergents, water, and smoke.
16
Q
Which amino acid is increased in the blood of patients with PKU?
A
Phenylalanine
17
Q
What may result if blood PKU is drawn before 24 hours of age?
A
False negative
18
Q
Which amino acids are increased in maple syrup disease?
A
Leucine, isoleucine, and valine
19
Q
What is bilirubin?
A
Byproduct of heme catabolism
20
Q
Which protein transports bilirubin in the blood?
A
Albumin
21
Q
Explain what happens to bilirubin in the liver.
A
It is conjugated with glucaronic acid by the enzyme UDPG. After conjugation, it is excreted into the intestines via bile duct and is reduced by bacteria into urobilinogen.
22
Q
What is the significance of clay-colored or light stools?
A
Obstruction of bile duct. Urobilin is not being produced because bilirubin is not reaching the intestines.
23
Q
What urine abnormality is seen with complete obstruction of the biliary tract?
A
Decreased urobilinogen
24
Q
Compare the solubility of direct and indirect bilirubin.
A
Direct bilirubin is soluble in water, indirect is not.
25
Which form of bilirubin can be excreted in the urine?
Only direct
26
What is a common method to measure bilirubin levels?
Diazo reaction
27
Name 2 accelerators that are used in total bilirubin reaction.
Alcohol or caffeine .
28
Two sources of error that can decrease the level of bilirubin
Exposure to light and hemolysis
29
Total bilirubin normal range
0.2 - 1.0 mg/dL
30
What would cause an increase in total bilirubin with a normal concentration of direct bilirubin
Prehepatic jaundice
31
What causes physiologic jaundice of the newborn?
Bilirubin metabolism is impaired because the newborn's immature liver doesn't produce the enzyme required for bilirubin conjugation.
32
In HDNB, which fraction of bilirubin is elevated or why?
Indirect due to excessive breakdown of RBCs by maternal antibody.
33
What is the risk to the newborn from a high level of indirect bilirubin?
Indirect bilirubin has a high affinity for brain tissue and necrosis (kernicterus)
34
What method is used to determine neonatal bilirubin?
Direct spectrophotometry at 454 nanometers.
35
Name two conditions in which direct bilirubin is elevated.
Hepatic and posthepatic jaundice
36
What are the typical lab findings in posthepatic jaundice?
Increased total bilirubin and direct bilirubin, decrease urine urobilinogen, and clay colored stool
37
Which disorder results in the highest levels of conjugated bilirubin?
Obstruction liver disease
38
What type of method is used for most hormone assays?
Immunoassays
39
What is the precursor in the biosynthesis of all steroid hormones?
Cholesterol
40
List 5 steroid hormones
Cortisol, aldosterone, estrogen, testosterone, and progesterone
41
Which endocrine gland releases tropic hormones that regulate other endocrine glands?
Anterior pituitary
42
Where is growth hormone (GH) produced and what is its main action?
Anterior pituitary and stimulates protein synthesis and cell growth/division
43
Where is FSH produced and what is its main action?
Anterior pituitary and stimulates egg/sperm production.
44
Where is TSH produced and what is its main action?
Anterior pituitary and stimulates T3 and T4 production by the thyroid
45
Where is ACTH produced and what is its main action?
Anterior pituitary and stimulates adrenal cortex to produce corticosteroids
46
Where is ADH produced and what is its main action?
Hypothalamus and stored in posterior pituitary. And it regulates reabsorption of water from distal convoluted tubules.
47
Where is cortisol produced and what is its main action?
Adrenal cortex and regulates fat, carbs, and protein metabolism, water and electrolyte balance, and suppresses inflammatory and allergic reactions.
48
What is Addison's disease?
Adrenal insufficiency, with decreased cortisol and increased ACTH.
49
What is Cushing's syndrome?
Elevated cortisol with tumors in pituitary or adrenal glands, .
50
Where is aldosterone produced and what is its main function?
Adrenal cortex and increases retention of sodium and excretion of potassium and hydrogen.
51
What are catecholamines?
Hormones secreted by the adrenal-medulla (epinephrine, norepinephrine, and dopamine)
52
Where is progesterone produced and what is its main action?
Ovaries and prepares uterus for pregnancy and stimulates lactation
53
What is the major estrogen produced by the ovaries?
Estradiol (E2)
54
Which hormones are used to asses fetal well-being?
Estriol and progesterone
55
Which hormone is used to detect pregnancy?
HCG
56
Which hormone can be measured by a home testing kit to determine the time of ovulation?
Luteinizing hormone (LH) secreted by the anterior pituitary
57
Why are estrogen and progesterone receptor assays performed?
To establish a prognosis for patients with breast cancer
58
Where is T4 produced and what is its main action?
Thyroid and controls metabolic rate, growth, and development, and sexual maturation.
59
Which is the physiologically active form of T4?
Free T4 but most T4 is bound to TBG protein
60
What is the recommended screening test for thyroid function?
TSH because it may be increased before symptoms and normal TSH excludes a primary thyroid problem.
61
What further thyroid testing is recommended when the TSH is abnormal?
Free T4
62
What further thyroid testing is recommended when TSH is low and free T4 is low/normal?
Total T3
63
How can primary hypothyroidism be differentiated from secondary?
Primary will have increased TSH as pituitary tries to stimulate thyroids to produce more T3 and T4. Secondly is a pituitary disorder with low TSH.
64
What are typical lab findings for primary hypothyroidism?
High TSH and low free T4.
65
What are typical lab findings for hyperthyroidism?
Low TSH and high free T4
66
What is Grave's disease?
Autoimmune disease that is most common hyperthyroid disorder in US
67
Where is PTH produced and what is its main function?
Parathyroid gland and increases serum calcium and decreases phosphates
68
Where is glucagon produced and what is its main function?
Alpha cells of pancreas and increases glucose levels
69
What are electrolytes?
Substances that carry electrical charge when dissolved in water
70
What are the major electrolytes
Sodium, potassium, chloride, and bicarbonate
71
What is the major extracellular cation
Sodium
72
What is the major intracellular cation
Potassium
73
What is the major extracellular anion
Chloride
74
What is the major intracellular anion
Phosphate
75
Normal sodium range
135-145 mEq/L
76
Which hormone regulates sodium concentration
Aldosterone
77
How are sodium and potassium usually measured
ISE (ion selective electrodes)
78
Why is potassium slightly higher in serum than in plasma
Potassium is released from platelets during clotting
79
Before reporting elevated potassium, what must be checked
Hemolysis or excessive delay in operating the serum/plasma from the RBCs
80
What clinical condition results from very high or very low potassium levels
Cardiac arrhythmias
81
What is chlorides role in the body
Maintains hydration, osmotic pressure, and electrolyte balance
82
Which disease is characterized by a high concentration of sodium and chloride in sweat?
Cystic fibrosis
83
What is the most accepted test for diagnosis of cystic fibrosis
The sweat test.
84
Which sweat test is recommended by the Cystic Fibrosis Foundation?
Gibson-Cooke quantitative sweat test
85
Anion gap formula
(Na + K) - (Cl + Co2)
86
What is the most abundant mineral in the body
Calcium
87
What anticoagulants cause a false decrease in calcium?
EDTA, citrate, and oxalate. All prevent coagulation by binding calcium.
88
Which form of calcium is physiologically active?
Ionized
89
Why is pH an important consideration in ionized calcium determinations
As pH decreases, calcium dissociates from it complexed forms, increasing free ionized calcium in serum
90
What is the reference method for total calcium
Atomic absorption
91
What happens to calcium when phosphorus is increased
It decreases. There is a reciprocal relationship between calcium and phosphorus
92
What substances regulate calcium levels
PTH, calcitonin, and vitamin D
93
What is tetany
Muscle cramps, spasms, and irritability due to decreased calcium or magnesium
94
What happens to calcium when phosphorus is increased
It decreases. There is a reciprocal relationship between calcium and phosphorus
95
Phosphorus is _______ in growing children than in adults.
Higher
96
What must be done to urine prior to performing a urine phosphorus analysis
Acidified to pH of 6 to prevent precipitation
97
How does hemolysis affect iron level
Falsely elevated results because of high iron concentration in hemoglobin
98
Which protein transports iron
Transferrin
99
Where is most of the iron in the body
Hemoglobin
100
2 storage forms of iron
Ferritin (primary storage form) and hemosiderin
101
How are the iron and TIBC affected in iron deficiency anemia
Serum iron is decreased and TIBC is increased.
102
TIBC is in indirect measurement of?
Transferrin
103
What is the most sensitive test for detection of iron deficiency anemia?
Serum ferritin - decreased means iron deficient
104
What happens to lactate in blood following collection
Increases due to glycolysis
105
What is a colligative property
One that depends on number of solute particles, regardless of size or weight. The colligative properties are osmotic pressure, vapor pressure, boiling point, and freezing point.
106
How is osmolality measured in clinical labs
Freezing point depression
107
What does the urine to serum osmolality ration indicate
Degree to which the kidneys concentrate the glomerular filtrate
108
Formula for calculated osmolality
2 Na+ + glucose/20 + BUN/3
109
Osmolal gap
Difference between calculated osmolality and measured.
110
Define pH
log [H+]
111
Henderson-Hasselbalch formula
6.1 + log [HCO3]/[H2CO3]
112
Normal pH for arterial blood
7.35 - 7.45
113
Acidosis
Blood pH <7.35 and result of decreased bicarb:carbonic acid ratio
114
Alkalosis
Blood pH >7.45 and result of increased bicarb:carbonic acid ratio
115
What is a buffer?
A weak acid and its salt. It minimizes change in pH.
116
How do the lungs affect blood pH
By regulating PCO2 and carbonic acid concentration. Hyperventilation decreases PCO2 and Hypoventilation increases PCO2/carbonic acid ratio.
117
What are the typical lab findings in respiratory acidosis
Decreased pH, increased PCO2, and normal bicarb. Kidneys will compensate by retaining bicarb.
118
What are the typical lab findings in respiratory alkalosis
Increased pH, decreased PCO2, and normal bicarb. Kidneys will compensate by excreting bicarb
119
What are the typical lab findings in metabolic acidosis
Decreased pH and bicarb, normal PCO2. Lung will compensate through hyperventilation to reduce carbonic acid.
120
Typical lab findings in metabolic alkalosis
Increased pH and bicarb, normal PCO2. Lungs will attempt to compensate through hypoventilation to increase carbonic acid.
121
Relationship between pH and H+ concentration?
Inverse
122
What is the relationship between pH and PCO2?
Inverse
123
If patient was hyperventilating, how would blood gas be affected
PCO2 would be decreased, pH increased, PO2 increased
124
What is the compensatory mechanism to reestablish pH in a patient with high HCO3 level?
Hypoventilation
125
What specimen is needed for blood gasses?
Heparinized arterial blood
126
If patient was hyperventilating, how would blood gas be affected
PCO2 would be decreased, pH increased, PO2 increased
127
If arterial blood sample was held at room temp for one hour before testing, how would the results be affected?
Cells would continue to use oxygen and produce carbon dioxide so PO2 would decreased and PCO2 would increase. pH would decrease
128
What is P50
Partial pressure of oxygen at which oxygen saturation is 50%
129
How is the oxygen dissociation curve affected by decreased 2,3-DPG
It is shifted to left. Increased affinity for hemoglobin for oxygen results in decreased release of oxygen to the tissues
130
How can altered urine specimen for drug testing be detected
Specific gravity less than 1.003 and creatinine less than 20 mg/dL
131
Creatinine clearance formula
Urine creatinine / serum creatinine X Urine volume / time
