CC - ONLINE EXAM Flashcards

Question

25. Water produced using either an anion or a cation EXCHANGE RESIN, followed by replacement of the removed ions with hydroxyl or hydrogen ions. A. Deionized water B. Distilled water C. RO water

Answer 1

A. Deionized water

Answer 2

D. USP and NF chemical grade

Answer 3

B. Kilogram Rationale: BASE QUANTITY 1. Length (meter) 2. Mass (kilogram) 3. Time (second) 4. Electric current (ampere) 5. Thermodynamic temperature (Kelvin) 6. Amount of substance (mole) 7. Luminous intensity (Candela)

Answer 4

A. pH Rationale: The properties of osmotic pressure, vapor pressure, freezing point, and boiling point are called COLLIGATIVE PROPERTIES. When a solute is dissolved in a solvent, these colligative properties change in a predictable manner for each osmole of substance present: ● FREEZING POINT IS LOWERED by −1.86°C ● VAPOR PRESSURE IS LOWERED by 0.3 mm Hg or torr ● OSMOTIC PRESSURE IS INCREASED by a factor of 1.7 × 104 mm Hg or torr ● BOILING POINT IS RAISED by 0.52°C

Answer 5

B. Moderate

Answer 6

C. Class C Rationale: Fires have been divided into four classes based on the nature of the combustible material and requirements for extinguishment: ● Class A: ordinary combustible solid materials, such as paper, wood, plastic, and fabric ● Class B: flammable liquids/gases and combustible petroleum products ● Class C: energized electrical equipment ● Class D: combustible/reactive metals, such as magnesium, sodium, and potassium

Answer 7

A. 1 and 2 Rationale: TYPE OF EXTINGUISHER (Bishop page 47) ● Class A: Pressurized water and dry chemical ● Class B: Dry chemical and carbon dioxide ● Class C: Dry chemical, carbon dioxide and halon ● Class D: Metal X

Answer 8

C. Shock Rationale: Liquid nitrogen is probably one of the most widely used cryogenic fluids (liquefied gases) in the laboratory. There are, however, several hazards associated with the use of any cryogenic material: fire or explosion, asphyxiation, pressure buildup, embrittlement of materials, and tissue damage similar to that of thermal burns.

Answer 9

C. Ergonomic hazards Rationale: The primary contributing factors associated with repetitive strain disorders are position/posture, applied force, and frequency of repetition. Remember to consider the design of hand tools (e.g., ergonomic pipets), adherence to ergonomically correct technique, and equipment positioning when engaging in any repetitive task. Chronic symptoms of pain, numbness, or tingling in extremities may indicate the onset of repetitive strain disorders. Other hazards include acute musculoskeletal injury. Remember to lift heavy objects properly, keeping the load close to the body and using the muscles of the legs rather than the back. Gradually increase force when pushing or pulling, and avoid pounding actions with the extremities.

Answer 10

B. Turn instrument off and unplug it Rationale: Before REPAIR OR ADJUSTMENT of electrical equipment The following should be done 1. unplug the equipment 2. make sure the hands are dry 3. remove jewelry.

Answer 11

A. Pull the person away from the electrical source

Answer 12

B. Incandescent tungsten or tungsten-iodide lamp

Answer 13

A. Deuterium discharge lamp and mercury arc lamp

Answer 14

A. Photomultiplier Rationale: Because of this amplification, the PM tube is 200 times more sensitive than the phototube. PM tubes are used in instruments designed to be extremely sensitive to very low light levels and light flashes of very short duration.

Answer 15

B. Tungsten–halogen lamp Rationale: ● Slide technology depends on reflectance spectrophotometry. ● For colorimetric determinations, the light source is a tungsten–halogen lamp.

Answer 16

A. Hollow-cathode lamp Rationale: The usual light source, known as a hollow-cathode lamp, consists of an evacuated gas-tight chamber containing an anode, a cylindrical cathode, and an inert gas, such as helium or argon.

Answer 17

C. 1 and 2 Rationale: Nephelometry and turbidimetry are used to measure the concentrations of large particles (such as antigen–antibody complexes, prealbumin, and other serum proteins) that because of their size cannot be measured by absorption spectroscopy

Answer 18

B. Inversely proportional

Answer 19

A. Increase in fluorescence

Answer 20

C. Nephelometry

Answer 21

C. Scintillation counter

Answer 22

A. Continuous flow analysis

Answer 23

A. Discrete analyzers Rationale: All three can use batch analysis (i.e., large number of specimens in one run), but only discrete analyzers offer random-access, or stat, capabilities.

Answer 24

C. Function verification Rationale: Function verification includes monitoring temperature, setting electronic parameters, calibrating instruments and analyzing control data.

Answer 25

o Mean o Median o Mode

Answer 26

o Coefficient of variation o Range o Standard deviation Rationale: The spread represents the relationship of all the data points to the mean. There are three commonly used descriptions of spread: (1) range (2) standard deviation (SD), and (3) coefficient of variation (CV).

Answer 27

o Fluctuations in line voltage o Reagent lot variability o Wear and tear of instrument Rationale: A SYSTEMATIC ERROR, on the other hand, will be seen as a trend in the data. Control values gradually rise (or fall) from the previously established limits. This type of error includes improper calibration, deterioration of reagents, sample instability, instrument drift, or changes in standard materials. All the Westgard rules that indicate trends identify systematic errors. 2(2S), 4(1S) and 10(x) rule. SYSTEMATIC ERRORS MAY BE DUE TO: ● Aging reagents ● Aging calibrators ● Instrument components ● Optical changes ● Fluctuations in line voltage ● Wear and tear of instrument ● Reagent lot variability ● Calibration differences ● Technologist interactions

Answer 28

o Reagent dispensing o Variation in handling techniques: pipetting, mixing, timing o Variation in operator Rationale: RANDOM ERROR is one with no trend or means of predicting it. Random errors include such situations as mislabeling a sample, pipetting errors, improper mixing of sample and reagent, voltage fluctuations not compensated for by instrument circuitry, and temperature fluctuations. Violations of the 1(2S), 1(3S) and R(4S) Westgard rules are usually associated with random error. To assess the situation, the sample is assayed using the same reagents. If a random error occurred, the same mistake may not be made again, and the result will be within appropriate control limits. RANDOM ERRORS MAY BE DUE TO: ● Reagent dispensing ● Sample evaporation ● Temperature of analyzer ● Electro-optical mechanism ● Calibrator reconstitution ● Environmental conditions ● Instability of instrument ● Variation in handling techniques: pipetting, mixing, timing ● Variation in operators

Answer 29

C. Mode Rationale: The mode is the most frequently occurring value in a dataset. Although it is seldom used to describe data, it is referred to when in reference to the shape of data, a bimodal distribution, for example.

Answer 30

A. Constant systematic error

Answer 31

B. Proportional systematic error

Answer 32

A. Bias Rationale: Bias: Difference between the observed mean and the reference mean. Negative bias indicates that the test values tend to be lower than the reference value, whereas positive bias indicates test values are generally higher. Bias is a type of constant systematic error.

Answer 33

C. Diagnostic sensitivity

Answer 34

D. Diagnostic specificity

Answer 35

A. Analytic sensitivity

Answer 36

B. Analytic specificity

Answer 37

C. Chance of an individual having a given disease or condition if the test is abnormal.

Answer 38

D. Chance an individual does not have a given disease or condition if the test is within the reference interval.

Answer 39

C. 95.45% Rationale: ● 68.26% will lie within ±1s ● 95.45% will lie within ±2s ● 99.74% will lie within ±3s

Answer 40

B. 2:2S Rationale: Westgard multirule is a control procedure that utilizes control rules to assess numerical quality control data; the control rules establish the limits for data rejection in a system with two controls. Other rules apply when three controls are used. 1:2s = 1 control value exceeds the mean ±2 standard deviations; warning rule that triggers inspection of control values using the other rejection rules that follow; only rule that is not used to reject a run; results are reportable 1:3s = 1 control value exceeds the mean ±3 standard deviations; detects random error 2:2s = 2 consecutive control values exceed the same 2 standard deviation limit (same mean +2 s or same mean -2 s); detects systematic error R:4s = 1 control value in a group exceeds the mean +2 s and a second control value exceeds the mean -2 s, creating a 4 standard deviation spread; detects random error 4:ls = 4 consecutive control values are recorded on one side of the mean and exceed either the same mean +1 s or the same mean -1 s; detects systematic error 10:x =10 consecutive control values are recorded on one side of the mean (either above or below the mean); detects systematic error

Answer 41

B. Two controls in the same run are greater than 4s units apart Rationale: The R:4s rule is applied to two control levels within the same run. The rule is violated when the algebraic difference between them (level 1 – level 2) exceeds 4s. The R:4s rule detects random error (error due to poor precision).

Answer 42

B. Systematic error Rationale: Random error: error varies from sample to sample

Answer 43

A. Random error Rationale: Random errors are deviations from the true value caused by unavoidable errors inherent in laboratory measurements. The standard error of the mean is a statistical concept reflecting sampling variation. It is the standard deviation of the entire population. Parametric statistics refer to a Gaussian (normal) distribution of data. Nonparametric statistics are more general and require no assumptions.

Answer 44

A. Deterioration of the reagent

Answer 45

A. Levy–Jennings Rationale: The Levy–Jennings plot is a graph of all QC results with concentration plotted on the y axis and run number on the x axis.

Answer 46

B. Tonks–Youden Rationale: The Tonks–Youden plot is used for interlaboratory comparison of monthly means. The method mean for level 1 is at the center of the y axis and mean for level 2 at the center of the x axis. Lines are drawn from the means of both levels across the graph, dividing it into four equal quadrants. If a laboratory’s monthly means both plot in the lower left or upper right, then systematic error (SE) exists in its method.

Answer 47

C. Cusum Rationale: Cusum points are the algebraic sum of the difference between each QC result and the mean. The y axis is the sum of differences and the x axis is the run number. The center of the y axis is 0. Because QC results follow a random distribution, the points should distribute about the zero line. Results are out of control when the slope exceeds 45° or a decision limit (e.g., ±2.7s) is exceeded.

Answer 48

C. Accuracy Rationale: The accuracy of an analytical result is the closeness with which the measured value agrees with the true value. Precision is reproducibility. Accuracy and precision are independent, but it is the goal of the clinical laboratory to design methods that are both precise and accurate.

Answer 49

B. Precision Rationale: Accuracy is easy to define but difficult to establish and maintain. Precision is relatively easy to measure and maintain.

Answer 50

A. Reliability Rationale: The reliability of an analytical procedure is its ability to maintain accuracy and precision over an extended period of time during which supplies, equipment, and personnel in the laboratory may change. It is often used interchangeably with the term "consistency." It is the goal of every clinical laboratory to produce reliable results.

Answer 51

A. Student’s t test Rationale: T TEST: COMPARES MEANS, ACCURACY F TEST: COMPARES S.D., PRECISION Student’s t test is the ratio of mean difference to the standard error of the mean difference (bias/random error) and tests for a significant difference in means. The F test is the ratio of variances and determines if one method is significantly less precise.

Answer 52

D. 120 minutes (2 hours)

Answer 53

B. 5 to 15 mg/dL Rationale: Reduction methods also measure other reducing sugars.

Answer 54

A. Glucose oxidase Rationale: Glucose oxidase is the most specific enzyme reacting with only beta D-glucose. Glucose oxidase converts beta D-glucose to gluconic acid. Mutarotase may be added to the reaction to facilitate the conversion of alpha-D-glucose to beta-D-glucose.

Answer 55

C. Glucose-6-phosphate dehydrogenase (G6PD) Rationale: The hexokinase method is considered more accurate than the glucose oxidase methods because the coupling reaction using glucose-6-phosphate dehydrogenase is highly specific; therefore, it has less interference than the coupled glucose oxidase procedure.

Answer 56

B. Hemolysis Rationale: Hemolyzed samples require a serum blank correction (subtraction of the reaction rate with hexokinase omitted from the reagent).

Answer 57

B. False decrease Rationale: Generally accepted as the reference method, hexokinase method is not affected by ascorbic acid or uric acid. Gross hemolysis and extremely elevated bilirubin may cause a false decrease in results.

Answer 58

A. Type 1 diabetes mellitus

Answer 59

B. Type 2 diabetes mellitus

Answer 60

B. Data represents an impaired glucose status Rationale: Resting plasma glucose ● NORMAL <140 ● IMPAIRED 140 – 199 ● DIAGNOSTIC ≥ 200 mg/dL Fasting plasma glucose ● NORMAL <100 ● IMPAIRED 100 – 125 ● DIAGNOSTIC ≥ 126 mg/dL 2-hour OGTT ● NORMAL <140 ● IMPAIRED 140 – 199 ● DIAGNOSTIC ≥ 200 mg/dL HbA1c ● NORMAL <5.7 % ● IMPAIRED 5.7 – 6.4% ● DIAGNOSTIC ≥ 6.5%

Answer 61

B. 6.5% Rationale: If the result is 6.5% or more, the treatment plan should be adjusted to achieve a lower level, and the test performed every 3 months until control is improved.

Answer 62

B. Red blood cell life span Rationale: Two factors determine the glycosylated hemoglobin levels: the average glucose concentration and the red blood cell life span. If the red blood cell life span is decreased because of another disease state such as hemoglobinopathies, the hemoglobin will have less time to become glycosylated and the glycosylated hemoglobin level will be lower.

Answer 63

B. Fructosamine Rationale: FRUCTOSAMINE: GLYCOSYLATED ALBUMIN Fructosamine assays are the most widely used to assess short-term (3 to 6 weeks) glycemic control because the average half-life of the proteins is 2–3 weeks.

Answer 64

B. Gluconeogenesis Rationale: ● Glycolysis: Metabolism of glucose molecule to pyruvate or lactate for production of energy ● Gluconeogenesis: Formation of glucose-6-phosphate from noncarbohydrate sources ● Glycogenolysis: Breakdown of glycogen to glucose for use as energy ● Glycogenesis: Conversion of glucose to glycogen for storage ● Lipogenesis: Conversion of carbohydrates to fatty acids ● Lipolysis: Decomposition of fat

Answer 65

B. Glucagon Rationale: Glucagon is the primary hormone responsible for increasing glucose levels. It is synthesized by the ALPHA-cells of islets of Langerhans in the pancreas and released during stress and fasting states. ACTION OF GLUCAGON ● Increases glycogenolysis: glycogen → glucose ● Increases gluconeogenesis: fatty acids → acetyl-CoA → ketone, proteins → amino acids

Answer 66

D. Insulin Rationale: Insulin is the only hormone that decreases glucose levels and can be referred to as a hypoglycemic agent. Insulin is the primary hormone responsible for the entry of glucose into the cell. It is synthesized by the beta cells of islets of Langerhans in the pancreas. It decreases plasma glucose levels by increasing the transport entry of glucose in muscle and adipose tissue by way of nonspecific receptors. It also regulates glucose by increasing glycogenesis, lipogenesis, and glycolysis and inhibiting glycogenolysis. ACTION OF INSULIN ● Increases glycogenesis and glycolysis: glucose → glycogen → pyruvate → acetyl-CoA ● Increases lipogenesis ● Decreases glycogenolysis

Answer 67

A. Hyperglycemia Rationale: Hypercortisolism = Cushing's Syndrome = Thyroid Problem CORTISOL INCREASES BLOOD GLUCOSE.

Answer 68

A. Below 50 mg/dL

Answer 69

A. Type 1 DM

Answer 70

B. Type 2 DM

Answer 71

B. 50 grams Rationale: ORAL LACTOSE TOLERANCE TESTS, measuring the increase in plasma glucose or galactose following ingestion of lactose, have been used to diagnose lactase deficiency.

Answer 72

D. Diagnosis of monoclonal gammopathies

Answer 73

D. All of these

Answer 74

C. Proteinuria

Answer 75

A. Negatively, anode

Answer 76

B. BCG (Bromcresol green)

Answer 77

B. Bromcresol purple (BCP) Rationale: BCP is more specific for albumin than BCG.

Answer 78

C. Dehydration

Answer 79

A. Prolonged tourniquet application

Answer 80

A. Microalbuminuria

Answer 81

A. Glutamine Rationale: Glutamine is the most abundant amino acid in the body, being involved in more metabolic processes than any other amino acid.

Answer 82

D. Tyrosine Rationale: Tyrosine is a precursor of the adrenal hormones epinephrine, norepinephrine, and dopamine and the thyroid hormones, including thyroxine. It is important in overall metabolism, aiding in the functions of the adrenal, thyroid, and pituitary glands.

Answer 83

A. Albumin Rationale: Albumin is responsible for nearly 80% of the colloid osmotic pressure (COP) of the intravascular fluid, which maintains the appropriate fluid balance in the tissue.

Answer 84

A. Prealbumin Rationale: A low prealbumin level is a sensitive marker of poor nutritional status. When a diet is deficient in protein, hepatic synthesis of proteins is reduced, with the resulting decrease in the level of the proteins originating in the liver, including prealbumin, albumin, and β-globulins. Because prealbumin has a short half-life of approximately 2 days, it decreases more rapidly than do other proteins.

Answer 85

A. A decreased level of prealbumin

Answer 86

D. Prealbumin Rationale: Prealbumin is the transport protein for thyroxine and triiodothyronine (thyroid hormones); it also binds with retinol-binding protein to form a complex that transports retinol (vitamin A) and is rich in tryptophan.

Answer 87

B. Emphysema Pulmonary Emphysema Juvenile Hepatic Cirrhosis

Answer 88

D. Down syndrome Rationale: Conditions associated with an elevated AFP level include spina bifida, neural tube defects, abdominal wall defects, anencephaly (absence of the major portion of the brain), and general fetal distress. Low levels of maternal AFP indicate an increased risk for Down syndrome (Trisomy 21) and trisomy 18 (Edward Syndrome), while it is increased in the presence of twins and neural tube defects.

Answer 89

A. Alpha2-macroglobulin Rationale: In nephrosis, the levels of serum α2-macroglobulin may increase as much as 10 times because its large size aids in its retention. The protein is also increased in diabetes and liver disease. Use of contraceptive medications and pregnancy increase the serum levels by 20%.

Answer 90

D. Alpha1-acid glycoprotein Rationale: α1-Acid Glycoprotein (Orosomucoid) α1-Acid glycoprotein (AAG), a major plasma glycoprotein, is negatively charged even in acid solutions, a fact that gave it its name. This protein is produced by the liver and is an acute-phase reactant.

Answer 91

B. Beta2-microglobulin Rationale: β2-microglobulin is a single polypeptide chain that is the light chain component of human leukocyte antigens (HLAs). It is found on the surface of nucleated cells and is notably present on lymphocytes. Increased plasma levels of β2-microglobulin are associated with renal failure, lymphocytosis, rheumatoid arthritis, and systemic lupus erythematosus.

Answer 92

C. Fibronectin

Answer 93

D. Fetal fibronectin

Answer 94

B. Crosslinked C-telopeptides Rationale: Cross-linked C-telopeptides (CTXs) are proteolytic fragments of collagen I formed during bone resorption (turnover). CTX is a biochemical marker of bone resorption that can be detected in serum and urine.

Answer 95

A. Beta-trace protein Rationale: β-Trace protein (BTP; synonym prostaglandin D synthase) is a 168–amino acid, low-molecular-mass protein in the lipocalin protein family. Recently, it was verified that BTP was established as an accurate marker of CSF leakage. It has also been reported recently as a potential marker in detecting impaired renal function, although no more sensitive than cystatin C.

Answer 96

D. Cystatin C

Answer 97

A. Amyloid β42 (Aβ42) and Tau protein Rationale: In a symptomatic patient, low Aβ42 along with high Tau reflects an increased likelihood of Alzheimer disease, but it does not mean that the person definitely has Alzheimer disease. If a patient does not have abnormal levels of these proteins, then the dementia is more likely due to a cause other than Alzheimer disease.

Answer 98

D. Myoglobin Rationale: As a cardiac biomarker, myoglobin has been used in conjunction with troponin to help diagnose or rule out a heart attack. When striated muscle is damaged, myoglobin is released, elevating the blood levels. In an AMI, this increase is seen within 2 to 3 hours of onset and reaches peak concentration in 8 to 12 hours. Myoglobin is a small molecule freely filtered by the kidneys, allowing levels to return to normal in 18 to 30 hours after the AMI. Because of the speed of appearance and clearance of myoglobin, it is also a useful marker for monitoring the success or failure of reperfusion.

Answer 99

D. Troponin Rationale: ACUTE CORONARY SYNDROME/MYOCARDIAL INFARCTION Cardiac troponin (cTn) represents a complex of regulatory proteins that include troponin I (cTnI) and troponin T (cTnT) that are specific to heart muscle. cTnI and cTnT are the “gold standard” in the diagnosis of acute coronary syndrome (ACS). cTn should be measured in all patients presenting with symptoms suggestive of ACS, in conjunction with physical examination and ECG.

Answer 100

B. hs-CRP Rationale: HIGH-SENSITIVITY CRP Considered a GOOD PREDICTOR TEST for assessing cardiovascular risk CK-MB, TROPONIN AND MYOGLOBIN Used to assess if a myocardial infarction HAS OCCURRED

Answer 101

B. B-type natriuretic peptide Rationale: B-type (brain) natriuretic peptide (BNP) is used to determine if physical symptoms are related to congestive heart failure.

Answer 102

A. BNP and electrocardiogram Rationale: DIAGNOSIS OF CONGESTIVE HEART FAILURE: Until recently, this condition was diagnosed strictly on the basis of symptomatology and/or as a result of procedures such as echocardiography, but more recently a biomarker for this condition is the brain form or B-type natriuretic peptide (BNP), which has been approved as a definitive test for this condition and appears to be an excellent marker for early heart failure.

Answer 103

A. Albumin cobalt binding Rationale: Albumin cobalt binding is a test that measures ischemia-modified albumin, which is a marker for ischemic heart disease.

Answer 104

C. Chylomicron Rationale: These chylomicrons enter the blood through the lymphatic system, where they impart a turbid appearance to serum

Answer 105

D. Greater than 600 mg/dL Rationale: The appearance of the plasma or serum can be observed and noted after a minimum 12-hour fast. If the plasma is clear, the triglyceride level is probably less than 200 mg/dL. When the plasma appears hazy or turbid, the triglyceride level has increased to greater than 300 mg/dL, and if the specimen appears opaque and milky (lipemic, from chylomicrons), the triglyceride level is probably greater than 600 mg/dL. Note: 1. Clear plasma: TAG < 200 mg/dL 2. Hazy or turbid plasma: TAG > 300 mg/dL 3. Opaque or milky plasma: TAG > 600 mg/dL

Answer 106

D. Total cholesterol, triglyceride, HDL cholesterol, LDL cholesterol

Answer 107

D. In the fasting state, approximately 12 hours after eating Rationale: Blood specimens for lipid studies should be drawn in the fasting state at least 9 to 12 hours after eating. Although fat ingestion only slightly affects cholesterol levels, the triglyceride results are greatly affected. Triglycerides peak at about 4 to 6 hours after a meal, and these exogenous lipids should be cleared from the plasma before analysis.

Answer 108

A. Cholesterol Rationale: Total cholesterol screenings are commonly performed on nonfasting individuals. Total cholesterol is only slightly affected by the fasting status of the individual, whereas triglycerides, fatty acids, and lipoproteins are greatly affected.

Answer 109

Rationale: It is first necessary to hydrolyze the triglycerides to free fatty acids and glycerol. This hydrolysis step is catalyzed by the enzyme lipase. The glycerol is then free to react in the enzyme-coupled reaction system that includes glycerokinase, pyruvate kinase, and lactate dehydrogenase or in the enzyme-coupled system that includes glycerokinase, glycerophosphate oxidase, and peroxidase.

Answer 110

D. Chylomicrons Rationale: Chylomicrons, which contain apo B-48, are the largest and the least dense of the lipoprotein particles. HDL, the smallest and most dense lipoprotein particle, is synthesized by both the liver and the intestine.

Answer 111

D. LpX Rationale: Lipoprotein X is an abnormal lipoprotein present in patients with biliary cirrhosis or cholestasis and in patients with mutations in lecithin:cholesterol acyltransferase (LCAT), the enzyme that esterifies cholesterol.

Answer 112

C. Chylomicrons Rationale: From the epithelial cells, the chylomicrons are released into the lymphatic system, which transports chylomicrons to the blood. The chylomicrons may then carry the triglycerides to adipose tissue for storage, to organs for catabolism, or to the liver for incorporation of the triglycerides into very-low-density lipoproteins (VLDLs). Chylomicrons are normally cleared from plasma within 6 hours after a meal.

Answer 113

A. VLDL Rationale: VLDL transports the majority of endogenous triglycerides, while the triglycerides of chylomicrons are derived entirely from dietary absorption.

Answer 114

B. Cholesterol Rationale: The beta-lipoprotein fraction is composed of approximately 50% cholesterol, 6% triglycerides, 22% phospholipids, and 22% protein. The beta-lipoproteins, which are also known as the low-density lipoproteins (LDLs), are the principal transport vehicle for cholesterol in the plasma.

Answer 115

C. 50% Rationale: About 50% of the weight of HDL is protein, largely apo A-I and apo A-II. The HDL is about 30% phospholipid and 20% cholesterol by weight.

Answer 116

B. High-density lipoproteins (HDLs) Rationale: The HDLs, also known as the alpha-lipoproteins, have the greatest density of 1.063-1.210 g/mL and move the fastest electrophoretically toward the anode.

Answer 117

C. Coronary artery disease Rationale: The quantification of the HDL cholesterol level is thought to contribute in assessing the risk that an individual may develop coronary artery disease (CAD). There appears to be an inverse relationship between HDL cholesterol and CAD. With low levels of HDL cholesterol, the risk of CAD increases.

Answer 118

C. HDL-C concentration < 40 mg/dL Rationale: POSITIVE (INCREASED) RISK FACTORS ● Age: ≥ 45 y for men; ≥ 55 y or premature menopause for women ● Family history of premature CHD ● Current cigarette smoking ● Hypertension (blood pressure ≥ 140/90 mm Hg or taking antihypertensive medication) ● LDL-C concentration ≥ 160 mg/dL (≥ 4.1 mmol/L), with ≤ 1 risk factor ● LDL-C concentration ≥ 130 mg/dL (3.4 mmol/L), with ≥ 2 risk factors ● LDL-C concentration ≥ 100 mg/dL (2.6 mmol/L), with CH D or risk equivalent ● HDL-C concentration < 40 mg/dL (< 1.0 mmol/L) ● Diabetes mellitus = CH D risk equivalent ● Metabolic syndrome (multiple metabolic risk factors) NEGATIVE (DECREASED) RISK FACTORS ● HDL-C concentration ≥ 60 mg/dL (≥ 1.6 mmol/L) ● LDL-C concentration < 100 mg/dL (< 2.6 mmol/L)

Answer 119

A. Apoprotein A-I Rationale: Apoprotein A-I and apo A-II are the principal apoproteins of HDL, and low apo A-I has a high correlation with atherosclerosis. Conversely, apo-B100 is the principal apoprotein of LDL, and an elevated level is a major risk factor in developing coronary heart disease.

Answer 120

C. Apo-B100 Rationale: LDL primarily contains apo B-100 and is more cholesterol rich than other apo B–containing lipoproteins. Note: ● Apo-AI, Apo-AII = HDL ● Apo-B100 = LDL, VLDL ● Apo-B48 = chylomicrons

Answer 121

C. Triglyceride

Answer 122

C. Heparin-manganese Rationale: Either a dextran sulfate-magnesium chloride mixture or a heparin sulfate-manganese chloride mixture may be used to precipitate the LDL and VLDL cholesterol fractions. This allows the HDL cholesterol fraction to remain in the supernatant.

Answer 123

D. Apoprotein A-I deficiency Rationale: Deficiency of apo A-I is seen in Tangier disease, a familial hypocholesterolemia.

Answer 124

B. 210 Rationale: Once the total cholesterol, triglyceride, and HDL cholesterol are known, LDL cholesterol can be quantified by using the Friedewald equation LDL cholesterol = Total cholesterol — (HDL cholesterol + Triglyceride/5) In this example, all results are in mg/dL: LDL cholesterol = 300 - (50 + 200/5) = 300 - (90) = 210 mg/dL

Answer 125

D. Triglycerides over 400 mg/dL Rationale: LDL cholesterol may be calculated or measured directly: 1. Friedewald formula Indirect, not valid for triglycerides over 400mg/dL LDL cholesterol = total cholesterol — [HDL cholesterol + triglyceride/5] 2. Homogeneous assay uses detergents to block HDL and VLDL from reacting with the dye to form a colored chromogen product. An enzymatic cholesterol analysis is performed with only LDL cholesterol able to react.

Answer 126

C. – Chylomicrons →β→pre-β→α + Rationale: Although pre-β lipoprotein is lower in density than β lipoprotein, it migrates faster on agarose or cellulose acetate owing to its more negative apoprotein composition. LIPOPROTEINS 1. By electrophoresis From the origin: chylomicrons > beta (LDL) > prebeta (VLDL) > alpha (HDL) Anode 2. By ultracentrifugation From the least dense and largest: chylomicrons > VLDL > LDL > HDL most dense and smallest

Answer 127

E. B-VLDL Rationale: β-VLDL (‘floating β’ lipoprotein) is an abnormal lipoprotein that accumulates in type 3 hyperlipoproteinemia. It is richer in cholesterol than VLDL and apparently results from the defective catabolism of VLDL. The particle is found in the VLDL density range but migrates electrophoretically with or near LDL.

Answer 128

B. B-VLDL Rationale: Lp(a) has a density similar to LDL, but migrates similarly to VLDL on electrophoresis. Thus it can be detected when the d > 1.006 g/mL protein is examined electrophoretically. When Lp(a) is present in concentrations exceeding 20-30 mg/dL (i.e., when it contributes more than about 10 mg/dL to the LDL-C measurement) an additional band with pre-β mobility is also observed in the d > 1.006 kg/L fraction (hence the name sinking pre-β-lipoprotein).

Answer 129

A. Lp(a) Rationale: Lipoprotein (a) is an apolipoprotein that is more commonly referred to as Lp(a). Although it is related structurally to LDL, Lp(a) is considered to be a distinct lipoprotein class with an electrophoretic mobility in the prebeta region. Lp(a) is believed to interfere with the lysis of clots by competing with plasminogen in the coagulation cascade, thus increasing the likelihood of atherosclerotic cardiovascular disease.

Answer 130

D. Elevated VLDL and presence of chylomicrons Rationale: BLOOD LIPOPROTEIN PATTERNS IN PATIENTS WITH HYPERLIPOPROTEINEMIA ● Type I: Extremely elevated TG due to the presence of chylomicrons ● Type IIa: Elevated LDL ● Type IIb: Elevated LDL and VLDL ● Type III: Elevated cholesterol, TG; presence of B-VLDL ● Type IV: Elevated VLDL ● Type V: Elevated VLDL and presence of chylomicrons

Answer 131

A. Pre-renal azotemia

Answer 132

B. Renal azotemia

Answer 133

C. Post-renal azotemia

Answer 134

A. The catabolism of proteins and amino acids Rationale: Urea is generated by deamination of amino acids. Most is derived from the hepatic catabolism of proteins. Uric acid is produced by the catabolism of purines. Oxidation of pyrimidines produces orotic acid.

Answer 135

A. Oxidation of creatine

Answer 136

A. Alkaline picrate

Answer 137

B. Creatinine

Answer 138

B. Catabolism of purines Rationale: Uric acid is the principal product of purine (adenosine and guanosine) metabolism.

Answer 139

B. Cystatin C

Answer 140

B. Ammonia Rationale: Severe liver disease is the most common cause of altered ammonia metabolism. Therefore the monitoring of ammonia levels may be used to determine prognosis.

Answer 141

C. Hepatic coma Rationale: Hepatic coma is caused by accumulation of ammonia in the brain as a result of liver failure. The ammonia increases central nervous system pH and is coupled to glutamate, a central nervous system neurotransmitter, forming glutamine. Blood and cerebrospinal fluid ammonia levels are used to distinguish encephalopathy caused by cirrhosis or other liver disease from nonhepatic causes and to monitor patients with hepatic coma.

Answer 142

D. Urea Rationale: UREA > AMINO ACIDS > URIC ACID > CREATININE > CREATINE > AMMONIA Constituents in the plasma that contain the element nitrogen are categorized as being protein- or nonprotein-nitrogen compounds. The principal substances included among the nonprotein-nitrogen compounds are urea, amino acids, uric acid, creatinine, creatine, and ammonia. Of these compounds, urea is present in the plasma in the greatest concentration, comprising approximately 45% of the nonprotein-nitrogen fraction.

Answer 143

D. 64 mg/dL Rationale: 30 x 2.14 = 64.2 mg/dL When it is necessary to convert urea nitrogen values to urea, the concentration may be calculated easily by multiplying the urea nitrogen value by 2.14. This factor is derived from the molecular mass of urea (60 daltons) and the molecular weight of its two nitrogen atoms (28)

Answer 144

B. Sodium fluoride Rationale: With the urease reagent systems for the quantification of urea, the use of sodium fluoride must be avoided because of its inhibitory effect on this system.

Answer 145

D. Diabetes mellitus

Answer 146

A. The patient had two cigarettes 15 minutes prior to blood draw. Rationale: Cigarette smoking by the patient is a significant source of ammonia contamination. It is recommended that patients do not smoke for several hours before a specimen is collected.

Answer 147

A. Glomerular filtration rate is decreased by at least 50% Rationale: The assay for urea is only a rough estimate of renal function and will not show any significant level of increased concentration until the glomerular filtration rate is decreased by at least 50%. A more reliable single index of renal function is the test for serum creatinine. Contrary to urea concentration, creatinine concentration is relatively independent of protein intake (from the diet), degree of hydration, and protein metabolism.

Answer 148

D. Creatinine Rationale: The quantity of creatinine formed daily is a relatively constant amount because it is related to muscle mass. Therefore, it has been customary to quantify the creatinine present in a 24-hour urine specimen as an index of the completeness of the collection.

Answer 149

D. Uric acid Rationale: Uric acid may be quantified by reacting it with phosphotungstic acid reagent in alkaline solution.

Answer 150

A. Chronic renal failure Rationale: As renal function continues to be lost over time, chronic renal failure develops. Chronic renal failure is manifested by loss of excretory function, inability to regulate water and electrolyte balance, and increased production of parathyroid hormone, all of which contribute to the abnormal laboratory findings. The decreased production of erythropoietin causes anemia to develop.

Answer 151

D. Uric acid Rationale: Gout is a pathological condition that may be caused by a malfunction of purine metabolism or a depression in the renal excretion of uric acid. Two of the major characteristics of gout are hyperuricemia and a deposition of uric acid as monosodium urate crystals in joints, periarticular cartilage, bone, bursae, and subcutaneous tissue.

Answer 152

A. Lesch-Nyhan syndrome Rationale: Lesch-Nyhan syndrome is an X-linked genetic disorder (seen only in males) caused by the complete deficiency of hypoxanthine-guanine phosphoribosyltransferase, an important enzyme in the biosynthesis of purines.

Answer 153

A. Uric acid Rationale: An increase in serum uric acid levels may be seen during chemotherapy for leukemia. The cause of this is the accelerated breakdown of cell nuclei in response to the chemotherapy. Other proliferative disorders that may respond similarly are lymphoma, multiple myeloma, and polycythemia. It is important that serum uric acid be monitored during chemotherapy to avoid nephrotoxicity.

Answer 154

D. Biliverdin Rationale: It is biliverdin that is the immediate precursor of bilirubin formation. Mesobilirubinogen and urobilinogen represent intestinal breakdown products of bilirubin catabolism.

Answer 155

B. Azobilirubin Rationale: Diazo reagent is a mixture of sulfanilic acid, sodium nitrite, and hydrochloric acid. The mixing of sodium nitrite with hydrochloric acid forms nitrous acid, which in turn reacts with sulfanilic acid to form a diazonium salt. This diazotized sulfanilic acid mixture, when mixed with solubilized bilirubin, forms a red azobilirubin complex.

Answer 156

C. Uridine diphosphate glucuronyltransferase Rationale: In order for the bilirubin-albumin complex to reach the parenchymal cells of the liver, the complex must be transported from the sinusoids to the sinusoidal microvilli and into the parenchymal cell. The microsomal fraction of the parenchymal cell is responsible for the conjugation of bilirubin. It is here that bilirubin reacts with uridine diphosphate glucuronate in the presence of the enzyme uridine diphosphate glucuronyltransferase to form bilirubin diglucuronide.

Answer 157

B. Urobilin Rationale: In the colon, a portion of the urobilinogen is oxidized by the action of microorganisms to urobilin, which is excreted in the feces as an orange-brown pigment.

Answer 158

A. Albumin Rationale: In the colon, a portion of the urobilinogen is oxidized by the action of microorganisms to urobilin, which is excreted in the feces as an orange-brown pigment.

Answer 159

A. Jaundice Rationale: Jaundice may be caused by an increase in either the unconjugated or conjugated form of bilirubin. Such increases in bilirubin levels may be caused by prehepatic, hepatic, or posthepatic disorders.

Answer 160

A. Brain Rationale: Kernicterus refers to the accumulation of bilirubin in brain tissue that occurs with elevated levels of unconjugated bilirubin. This condition is most commonly seen in newborns with hemolytic disease resulting from maternal-fetal Rh incompatibility. Newborns afflicted with kernicterus will exhibit severe neural symptoms.

Answer 161

B. Urobilinogen Rationale: In the small intestine, urobilinogen is formed through the enzymatic reduction process of anaerobic bacteria on bilirubin.

Answer 162

D. Specimen refrigeration Rationale: ilirubin will deteriorate when exposed to either white or UV light. This deterioration is also temperature sensitive. Thus, specimens for bilirubin analysis should be stored in the dark at refrigerator temperature until the assay can be performed. Lipemia should be avoided, due to its interference with spectrophotometric analyses. Because hemoglobin reacts with diazo reagent, use of hemolyzed specimens should be avoided. Hemolysis will cause bilirubin results to be falsely low.

Answer 163

C. Delta Rationale: Four bilirubin fractions represented by Greek letters have been identified: unconjugated (alpha), monoconjugated (beta), diconjugated (gamma), and unconjugated bilirubin covalently bound to albumin (delta). Delta-bilirubin is normally present in low concentration in the blood, and it is known to react directly with diazotized sulfanilic acid. Increased serum levels of delta-bilirubin are associated with liver-biliary disease. According to Bishop: DELTA bilirubin is CONJUGATED bilirubin that is covalently bound to albumin.

Answer 164

A. Spleen Rationale: The cells of the reticuloendothelial system are responsible for the removal of old red blood cells from the peripheral circulation. As the red blood cells reach the end of their 120-day life span, the specialized cells mainly of the spleen phagocytize the aged cells and convert the released hemoglobin into the excretory pigment bilirubin.

Answer 165

A. Insoluble in water Rationale: Direct bilirubin was so named because of its ability in the van den Bergh method to react directly with diazotized sulfanilic acid without the addition of alcohol. Such a direct reaction is possible because direct bilirubin is conjugated in the liver with glucuronic acid, thereby making it a polar, water-soluble compound. Because conjugated bilirubin is both water soluble and not protein bound, it may be filtered through the glomerulus and excreted in the urine of jaundiced patients.

Answer 166

A. Conjugated bilirubin Rationale: Because conjugated bilirubin is both water soluble and not protein bound, it may be filtered through the glomerulus and excreted in the urine of jaundiced patients.

Answer 167

C. Caffeine-sodium benzoate Rationale: Unlike direct bilirubin, indirect-reacting bilirubin is insoluble in deionized water and dilute hydrochloric acid. Indirect-reacting bilirubin must first be mixed with methanol or caffeine-sodium benzoate to solubilize it before proceeding with the diazo reaction. Note: EVELYN-MALLOY: methanol JENDRASSIK-GROF: caffeine-sodium benzoate

Answer 168

D. Obstructive jaundice Rationale: "Obstructive jaundice" is a term applied to conditions in which the common bile duct is obstructed because of gallstone formation, spasm, or neoplasm. Such an obstruction blocks the flow of bile from the gallbladder into the small intestine. This impedance of bile flow will result in a backflow of bile from the gallbladder into the sinusoids of the liver and ultimately into the peripheral circulation. Because the liver is not initially involved and the disorder is of posthepatic origin, the increased levels of bilirubin in the blood are caused by the backflow of conjugated bilirubin.

Answer 169

A. Unconjugated serum bilirubin level increased Rationale: Hemolytic jaundice is also referred to as prehepatic jaundice. It is caused by excessive destruction of erythrocytes at a rate that exceeds the conjugating ability of the liver. As a result, increased levels of unconjugated bilirubin appear in the blood.

Answer 170

D. Deficiency in the bilirubin conjugation enzyme system Rationale: The enzyme uridine diphosphate glucuronyltransferase catalyzes the conjugation of bilirubin with glucuronic acid. In newborns, especially premature infants, this liver enzyme system is not fully developed or functional. Because of this deficiency in the enzyme system, the concentration of unconjugated bilirubin rises in the blood, because only the conjugated form may be excreted through the bile and urine. The increased levels of unconjugated bilirubin will cause the infant to appear jaundiced. Generally, this condition persists for only a short period because the enzyme system usually becomes functional within several days after birth.

Answer 171

D. Gilbert syndrome Rationale: Gilbert syndrome is a preconjugation transport disturbance. In this disorder the hepatic uptake of bilirubin is defective because the transportation of bilirubin from the sinusoidal membrane to the microsomal region is impaired.

Answer 172

B. Deficiency of the enzyme system required for conjugation of bilirubin Rationale: Both Crigler-Najjar syndrome and neonatal jaundice, a physiological disorder, are due to a deficiency in the enzyme-conjugating system. With a deficiency in uridine diphosphate glucuronyltransferase, the liver is unable to conjugate bilirubin, and both of these conditions are characterized by increased levels of unconjugated bilirubin. Unlike Crigler-Najjar syndrome, which is a hereditary disorder, neonatal physiological jaundice is a temporary situation that usually corrects itself within a few days after birth.

Answer 173

C. Inability to conjugate bilirubin Rationale: In Dubin-Johnson syndrome, the transport of conjugated (direct) bilirubin from the microsomal region to the bile canaliculi is impaired. In this rare familial disorder, plasma conjugated bilirubin levels are increased because of defective excretion of bilirubin in the bile. Because conjugated bilirubin is water soluble, increased amounts of bilirubin are found in the urine.

Answer 174

B. Hepatic cirrhosis Rationale: ● Gamma spike: multiple myeloma ● Beta-gamma bridging: hepatic cirrhosis ● α1 globulin flat curve: juvenile cirrhosis (AATdeficiency) ● Α2 globulin band spike: nephrotic syndrome ● Spikes in α1, α2 and β: inflammation

Answer 175

A. Hepatitis Rationale: ● HEPATITIS: less than 80% liver damage ● High: AST, ALT, LD, ALP, bilirubin ● Normal: Total protein, albumin, ammonia

Answer 176

B. Cirrhosis Rationale: ● CIRRHOSIS: 80% liver tissue damage ● Death of liver cells with regeneration leads to fibrosis, scarring and destruction of the normal liver architecture ● Low: Total protein, albumin ● High: Bilirubin, ammonia ● Normal to slightly high: ALP ● Normal: AST, ALT and LD

Answer 177

A. Cirrhosis Rationale: Cirrhosis is defined as destruction of the liver’s architecture. The leading cause of this condition is alcohol abuse.

Answer 178

C. B1 and B2 Rationale: Hemolytic jaundice: unconjugated bilirubin (B1) Hepatic jaundice: unconjugated and conjugated bilirubin (B1 and B2) Obstructive jaundice: conjugated bilirubin (B2)

Answer 179

C. Tissue damage and necrosis Rationale: The majority of serum enzymes that are of interest clinically are of intracellular origin. These enzymes function intracellularly, with only small amounts found in serum as a result of normal cellular turnover. Increased serum levels are due to tissue damage and necrosis, where the cells disintegrate and leak their contents into the blood. Thus, elevated serum levels of intracellular enzymes are used diagnostically to assess tissue damage.

Answer 180

A. Lower than expected Rationale: Factors that affect enzyme assays include temperature, pH, substrate concentration, and time of incubation. For each clinically important enzyme, the optimum temperature and pH for its specific reaction are known. When lower than optimum temperature or pH is employed, the measured enzyme activity will be lower than the expected activity value. As temperature increases, the rate of the reaction increases.

Answer 181

B. Enzymes are protein catalysts of biological origin. Rationale: Enzymes are protein in nature. Like all proteins, they may be denatured with a loss of activity as a result of several factors (e.g., heat, extreme pH, mechanical agitation, strong acids, and organic solvents). Enzymes act as catalysts for the many chemical reactions of the body. Enzymes increase the rate of a specific chemical reaction by lowering the activation energy needed for the reaction to proceed.

Answer 182

C. Lock-and-key theory by Emil Fischer Rationale: LOCK-AND-KEY (EMIL FISCHER) ● The shape of the key (substrate) must fit into the lock (enzyme) INDUCED-FIT (DANIEL KOSHLAND) ● Substrate binding to the active site of the enzyme

Answer 183

A. First-order kinetics Rationale: In 1913, Michaelis and Menten hypothesized the role of substrate concentration in formation of the enzyme–substrate (ES) complex. According to their hypothesis, the substrate readily binds to free enzyme at a low-substrate concentration. With the amount of enzyme exceeding the amount of substrate, the reaction rate steadily increases as more substrate is added. The reaction is following first-order kinetics because the reaction rate is directly proportional to substrate concentration. Eventually, however, the substrate concentration is high enough to saturate all available enzyme, and the reaction velocity reaches its maximum. When product is formed, the resultant free enzyme immediately combines with excess free substrate. The reaction is in zero-order kinetics, and the reaction rate depends only on enzyme concentration.

Answer 184

B. Zero-order kinetics

Answer 185

B. Kinetic assay Rationale: One of two general methods may be used to measure the extent of an enzymatic reaction: (1) fixed-time and (2) continuous-monitoring or kinetic assay. 1. In the fixed time method, the reactants are combined, the reaction proceeds for a designated time, the reaction is stopped (usually by inactivating the enzyme with a weak acid), and a measurement is made of the amount of reaction that has occurred. The reaction is assumed to be linear over the reaction time; the larger the reaction, the more enzyme is present. 2. In continuous-monitoring or kinetic assays, multiple measurements, usually of absorbance change, are made during the reaction, either at specific time intervals (usually every 30 or 60 seconds) or continuously by a continuous- recording spectrophotometer.

Answer 186

B. Coenzyme Rationale: A nonprotein molecule, called a cofactor, may be necessary for enzyme activity. Inorganic cofactors, such as chloride or magnesium ions, are called activators. A coenzyme is an organic cofactor, such as nicotinamide adenine dinucleotide (NAD). When bound tightly to the enzyme, the coenzyme is called a prosthetic group. The enzyme portion (apoenzyme), with its respective coenzyme, forms a complete and active system, a holoenzyme.

Answer 187

A. Activator

Answer 188

D. Transferases Rationale: There are six major classes of enzymes. The International Commission of Enzymes of the International Union of Biochemistry has categorized all enzymes into one of these classes: oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases. Transferases are enzymes that catalyze the transfer of groups, such as amino and phosphate groups, between compounds. Transferases frequently need coenzymes, such as pyridoxal-5'-phosphate (P-5-P), for the amino transfer reactions. Aspartate and alanine aminotransferases, creatine kinase, and gamma-glutamyltransferase are typical examples.

Answer 189

B. Aldolase Rationale: Hydrolases are enzymes that split molecules with the addition of water—for example, amylase, lipase, alkaline phosphatase, acid phosphatase, 5'-nucleotidase, and trypsin. They do not usually require coenzymes but often need activators. Aldolase and carbonic anhydrase are examples of the class of enzymes known as the lyases. Lyases are enzymes that split molecules between carbon-to-carbon bonds without the addition of water. The resulting products usually contain carbon double bonds.

Answer 190

C. Oxidoreductases

Answer 191

D. Ligases Rationale: In addition to naming enzymes, the IUB system identifies each enzyme by an EC numerical code containing four digits separated by decimal points. The first digit places the enzyme in one of the following six classes: 1. Oxidoreductases. Catalyze an oxidation–reduction reaction between two substrates 2. Transferases. Catalyze the transfer of a group other than hydrogen from one substrate to another 3. Hydrolases. Catalyze hydrolysis of various bonds 4. Lyases. Catalyze removal of groups from substrates without hydrolysis; the product contains double bonds 5. Isomerases. Catalyze the interconversion of geometric, optical, or positional isomers 6. Ligases. Catalyze the joining of two substrate molecules, coupled with breaking of the pyrophosphate bond in adenosine triphosphate (ATP) or a similar compound

Answer 192

A. Decreasing the activation energy

Answer 193

B. Pernicious anemia and hemolytic disorders

Answer 194

E. LD-5 Rationale: LD-5 is the most labile isoenzyme. Loss of activity occurs more quickly at 4°C than at 25°C. Serum samples for LD isoenzyme analysis should be stored at 25°C and analyzed within 24 hours of collection.

Answer 195

D. Paget's disease Rationale: Elevated ALP levels may be observed in various bone disorders. Perhaps the highest elevations of ALP activity occur in Paget’s disease (osteitis deformans). Other bone disorders include osteomalacia, rickets, hyperparathyroidism, and osteogenic sarcoma.

Answer 196

D. Bone disease Rationale: Increased serum creatine kinase (CK), formerly called creatine phosphokinase (CPK), values are caused primarily by lesions of cardiac muscle, skeletal muscle, or brain tissue. CK increases in the early stages of Duchenne-type progressive muscular dystrophy. Assays of total CK and CK isoenzymes are commonly used in the diagnosis of myocardial infarction. Hypothyroidism causes a moderate increase in CK values. Elevation of this enzyme also occurs after vigorous muscular activity, in cases of cerebrovascular accidents (stroke), and after repeated intramuscular injections.

Answer 197

A. Creatine kinase Rationale: To aid in the diagnosis of skeletal muscle disease, measurement of creatine kinase would be most useful. CK yields the most reliable information when skeletal muscle disease is suspected. Other enzymes that are also useful to measure are aspartate aminotransferase and lactate dehydrogenase. Both of these enzymes will be moderately elevated, whereas CK is significantly increased.

Answer 198

C. CK, AST, LD Rationale: When an AMI occurs, CK is the first enzyme to become elevated in the blood, rising within 4 to 6 hours following chest pain. AST exhibits a rise in the serum level within 6 to 8 hours. LD shows an increase in 8 to 12 hours following infarction. Measurement of these three enzymes to assess acute myocardial infarction has been replaced by cardiac troponin, myoglobin, and CK-MB.

Answer 199

C. Cholinesterase Rationale: Normal serum levels of cholinesterase are quite high, reflecting its continual synthesis and release by the liver. Decreased values are considered abnormal.

Answer 200

A. Amylase Rationale: AMYLASE is the smallest enzyme, with a molecular weight of 50,000 to 55,000 Da. Because of its small size, it is readily filtered by the renal glomerulus and also appears in the urine.

Answer 201

E. G6PD Rationale: Macroenzymes are high-molecular-mass forms of the serum enzymes (ACP, ALP, ALT, AMY, AST, CK, GGT, LD, and LPS) that can be bound to either an immunoglobulin (macroenzyme type 1) or a nonimmunoglobulin substance (macroenzyme type 2). Macroenzymes are usually found in patients who have an unexplained persistent increase of enzyme concentrations in serum. The presence of macroenzymes can also increase with increasing age.

Answer 202

B. CA-15-3

Answer 203

C. HER-2/neu

Answer 204

C. Nuclear matrix protein

Answer 205

A. Hepatoma

Answer 206

C. Potassium

Answer 207

C. Potassium Rationale: As the primary intracellular cation, potassium is an integral part of the transmission of nerve impulses. Movement of potassium across the nerve tissue membrane permits the neural signal to move down the nerve fiber. Potassium also seems to be involved in synaptic processes, where the impulse "jumps" from one nerve fiber to another.

Answer 208

C. Chloride

Answer 209

B. Chloride

Answer 210

A. Bicarbonate

Answer 211

B. Magnesium

Answer 212

B. Calcium and magnesium Rationale: Electrolytes are an essential component in numerous processes, including: 1. Volume and osmotic regulation (sodium [Na+], chloride [Cl−], potassium [K+]) 2. Myocardial rhythm and contractility (K+, magnesium [Mg2+], calcium [Ca2+]) 3. Cofactors in enzyme activation (e.g., Mg2+, Ca2+, zinc [Zn2+]) 4. Regulation of adenosine triphosphatase (ATPase) ion pumps (Mg2+) 5. Acid–base balance (bicarbonate HCO3−, K+, Cl−) 6. Blood coagulation (Ca2+, Mg2+) 7. Neuromuscular excitability (K+, Ca2+, Mg2+) 8. Production and use of ATP from glucose (e.g., Mg2+, phosphate PO4−)

Answer 213

C. Bicarbonate, potassium and chloride

Answer 214

B. Potassium Rationale: Hemolysis of blood specimens because of physiological factors is often difficult to differentiate from hemolysis produced by the blood collection itself. In either case, the concentration of potassium will be increased in the serum because of the release of the very high level of intracellular potassium from the erythrocytes into the plasma. When hemolysis is present, the serum concentrations of sodium, bicarbonate, chloride, and calcium will be decreased because their concentrations are lower in erythrocytes than in plasma.

Answer 215

D. Less than 135 mmol/L Rationale: Hyponatremia is defined as a serum/plasma level less than 135 mmol/L. Hyponatremia is one of the most common electrolyte disorders in hospitalized and nonhospitalized patients. Levels below 130 mmol/L are clinically significant. Hyponatremia can be assessed by the cause for the decrease or with the osmolality level.

Answer 216

C. Diuretic use

Answer 217

C. Plasma/serum osmolality Rationale: Hyponatremia can also be classified according to plasma/serum osmolality. Because Na+ is a major contributor to osmolality, both levels can assist in identifying the cause of hyponatremia. There are three categories of hyponatremia—low osmolality, normal osmolality, or high osmolality. Most instances of hyponatremia occur with decreased osmolality.

Answer 218

C. Pseudohyponatremia Rationale: Pseudohyponatremia can occur when Na+ is measured using indirect ion-selective electrodes (ISEs) in a patient who is hyperproteinemic or hyperlipidemic. An indirect ISE dilutes the sample prior to analysis and as a result of plasma/serum water displacement; the ion levels are falsely decreased.

Answer 219

D. Urine osmolality Rationale: The measurement of urine osmolality is necessary to evaluate the cause of hypernatremia. With renal loss of water, the urine osmolality is low or normal. With extrarenal fluid losses, the urine osmolality is increased.

Answer 220

A. Hypernatremia Rationale: Any condition that increases water loss, such as fever, burns, diarrhea, or exposure to heat, will increase the likelihood of developing hypernatremia.

Answer 221

C. Potassium Rationale: Potassium (K+) is the major intracellular cation in the body, with a concentration 20 times greater inside the cells than outside. Many cellular functions require that the body maintain a low ECF concentration of K+ ions. As a result, only 2% of the body’s total K+ circulates in the plasma. Functions of K+ in the body include regulation of neuromuscular excitability, contraction of the heart, ICF volume, and H+ concentration.

Answer 222

D. Vomiting

Answer 223

B. Alkalosis

Answer 224

B. Chloride Rationale: Chloride (Cl−) is the major extracellular anion. It is involved in maintaining osmolality, blood volume, and electric neutrality. In most processes, Cl− shifts secondarily to a movement of Na+ or HCO3 −.

Answer 225

C. Cystic fibrosis Rationale: Measuring the concentration of chloride in sweat is a commonly used diagnostic procedure for determining the disorder of cystic fibrosis (CF). The majority of patients with CF will present with increased concentrations of sodium and chloride in their sweat.

Answer 226

A. Bicarbonate Rationale: Bicarbonate is the second most abundant anion in the ECF. Total CO2 comprises the bicarbonate ion (HCO3−), H2CO3, and dissolved CO2, with HCO3− accounting for more than 90% of the total CO2 at physiologic pH. Because HCO3− composes the largest fraction of total CO2, total CO2 measurement is indicative of HCO3− measurement.

Answer 227

D. Magnesium Rationale: Magnesium (Mg2+) is the fourth most abundant cation in the body and second most abundant intracellular ion. The average human body (70 kg) contains 1 mol (24 g) of Mg2+. Approximately 53% of Mg2+ in the body is found in bone, 46% in muscle and other organs and soft tissue, and less than 1% is present in serum and RBCs.

Answer 228

A. Hypomagnesemia Rationale: Hypomagnesemia is most frequently observed in hospitalized individuals in intensive care units (ICUs) or those receiving diuretic therapy or digitalis therapy. These patients most likely have an overall tissue depletion of Mg2+ as a result of severe illness or loss, which leads to low serum levels. Hypomagnesemia is rare in nonhospitalized individuals.

Answer 229

D. Parathyroid hormone, vitamin D and calcitonin

Answer 230

A. Cresolphthalein complexone

Answer 231

B. Ammonium molybdate Rationale: Serum inorganic phosphate concentrations are determined most commonly by reacting with ammonium molybdate reagent. The molybdenum-phosphate complexes can be quantified at 340 nm. Alternately, treatment of the phosphomolybdate compound formed with a reducing agent leads to the formation of molybdenum blue, which can be measured spectrophotometrically.

Answer 232

o Hypernatremia o Ketoacidosis o Lactic acidosis o Methanol, ethanol, ethylene glycol poisoning o Uremia/renal failure

Answer 233

o Hypercalcemia o Hypoalbuminemia

Answer 234

A. Serum Rationale: Osmolality may be measured in serum or urine. Major electrolyte concentrations, mainly sodium, chloride, and bicarbonate, provide the largest contribution to the osmolality value of serum. Plasma use is not recommended because osmotically active substances may be introduced into the specimen from the anticoagulant.

Answer 235

D. 92 Rationale: For monovalent cations or anions the contribution to osmolality is approximately 92%. Other serum electrolytes, serum proteins, glucose, and urea contribute to the remaining 8%.

Answer 236

C. 2(Na) + (glucose ÷ 18) + (BUN ÷ 2.8)

Answer 237

C. Ferritin Rationale: In adults the total body iron content averages 3-4 g. The majority of this iron is found in the active pool as an essential constituent of hemoglobin, with a much lesser amount being an integral component of myoglobin and a number of enzymes. Approximately 25% of the body iron is found in inactive storage forms. The major storage form of iron is ferritin, with a lesser amount being stored as hemosiderin.

Answer 238

A. Lithium heparin; dry Rationale: Evacuated collection tubes are not appropriate for blood gases. While both dry (lyophilized) and liquid heparin are acceptable anticoagulants, the liquid form is not recommended because excessive amounts can dilute the sample and possibly alter the sample due to equilibration with room air.

Answer 239

A. pO2 and pH increase; pCO2 decreases Rationale: Note: OPEN TUBE (ENTRY OF OXYGEN) ⬆️ Increased pO2 ⬇️ Deceased pCO2 (H2CO3) ⬆️ Increased pH (ALKALINE) CLOSED TUBE (OXYGEN UTILIZED BY CELLS) ⬇️ Decreased pO2 ⬆️ Increased pCO2 (H2CO3) ⬇️ Decreased pH (ACIDIC)

Answer 240

C. pO2 decreases, pCO2 increases, pH decreases

Answer 241

A. Bicarbonate/carbonic acid Rationale: Because of its high concentration in blood, the bicarbonate/carbonic acid pair is the most important buffer system in the blood. This buffer system is also effective in the lungs and in the kidneys in helping to regulate body pH. The other buffers that also function to help maintain body pH are the phosphate, protein, and hemoglobin buffer systems.

Answer 242

B. 20:1 ratio of bicarbonate to carbonic acid

Answer 243

B. Carbon dioxide

Answer 244

C. Will decrease pO2 by 7%

Answer 245

B. Will increase pCO2 by 3%

Answer 246

A. Kidney function

Answer 247

B. Lung function

Answer 248

D. Metabolic alkalosis Rationale: An excess of bicarbonate without a change in pCO2 will increase the ratio of bicarbonate to carbonic acid. Therefore, the pH will increase; that is, the plasma becomes more alkaline.

Answer 249

B. pH 7.66 HCO3- 22 mmol/L pCO2 20 mm Hg Rationale: TIPS FOR EVALUATING ACID-BASE DISORDERS 1. Look at the pH: determine if acidosis or alkalosis 2. Compare pCO2 and HCO3- A. pCO2 going opposite to pH – RESPIRATORY Abnormal pCO2 respiratory [↓pH ↑pCO2 respiratory acidosis] [↑pH ↓pCO2 respiratory alkalosis] B. HCO3- going same direction as pH - METABOLIC Abnormal HCO3- metabolic [↓pH ↓HCO3- metabolic acidosis] [↑ pH ↑ HCO3- metabolic alkalosis] 3. If pH is normal, full compensation occurred 4. If main compensatory mechanism kicked in, but pH still out of normal range, partial compensation has occurred

Answer 250

A. pH 7.25 HCO3- 15 mmol/L pCO2 37 mm Hg

Answer 251

D. Metabolic alkalosis Rationale: A pH above 7.45 corresponds with alkalosis. Both bicarbonate and pCO2 are elevated. Bicarbonate is the conjugate base and is under metabolic (renal) control, while pCO2 is an acid and is under respiratory control. Increased bicarbonate (but not increased CO2) results in alkalosis; therefore, the classification is metabolic alkalosis, partially compensated by increased pCO2.

Answer 252

A. Anxiety

Answer 253

B. pCO2, HCO3- and pO2 Rationale: pH, pCO2, and pO2 are measured directly from the specimen by utilizing electrodes. The pH and PCO2 electrodes are potentiometric where the voltage produced across a semipermeable membrane to hydrogen ions or CO2 gas is proportional to the "activity" of those ions in the patient's sample. Activity is measured in voltage whose value can be presented in terms of concentration. pO2 is measured similarly, but using an amperometric electrode. Note: pH and pCO2 = POTENTIOMETRY pO2 = AMPEROMETRY

Answer 254

B. Occasionally Rationale: Mixed respiratory and nonrespiratory disorders occasionally arise from more than one pathologic process and represent the most serious of medical conditions as compensation for the primary disorder is failing.

Answer 255

A. Respiratory acidosis

Answer 256

C. Pituitary gland

Answer 257

A. Anterior pituitary gland

Answer 258

B. Posterior pituitary gland

Answer 259

o ACTH o FSH o LH o TSH

Answer 260

C. GH E. Prolactin

Answer 261

B. GH Rationale: Growth hormone (GH), also called somatotropin, is structurally related to prolactin and human placental lactogen.

Answer 262

A. Oral glucose loading

Answer 263

D. Amino acids

Answer 264

A. Anterior pituitary gland

Answer 265

A. Vasopressin deficiency

Answer 266

D. TSH assay Rationale: TSH is produced by the anterior pituitary in response to low levels of free T4 or T3. A normal TSH rules out thyroid disease. TSH is low in primary hyperthyroidism and high in primary hypothyroidism.

Answer 267

A. Primary hyperthyroidism Rationale: In primary hyperthyroidism, the TSH will be within a range of 0–0.02 mU/mL, while in nonthyroid illnesses it will be 0.03 mU/mL or higher.

Answer 268

A. Primary hyperthyroidism

Answer 269

D. All of these

Answer 270

A. Aldosterone Rationale: Zona glomerulosa (G-zone) cells (outer 10%) synthesize mineralocorticoids (aldosterone) critical for sodium retention (volume), potassium, and acid–base homeostasis. They have low cytoplasmic-to-nuclear ratios and small nuclei with dense chromatin with intermediate lipid inclusions.

Answer 271

B. Cortisol Zona fasciculata (F-zone) cells (middle 75%) synthesize glucocorticoids, such as cortisol and cortisone critical to blood glucose homeostasis and blood pressure.

Answer 272

B. Catecholamine Rationale: Medullary catecholamine products serve as firstresponders to stress by acting within seconds (cortisol takes 20 min) to promote the fight-or-flight response, which increases cardiac output and blood pressure, diverts blood toward muscle and brain, and mobilizes fuel from storage.

Answer 273

A. Excess secretion of pituitary ACTH Rationale: Cushing’s disease refers to adrenal hyperplasia resulting from misregulation of the hypothalamic–pituitary axis. It is usually caused by small pituitary adenomas. Cushing’s syndrome may be caused by Cushing’s disease, adrenal adenoma or carcinoma, ectopic ACTH-producing tumors, or excessive corticosteroid administration. The cause of Cushing’s syndrome can be differentiated using the ACTH and dexamethasone suppression tests.

Answer 274

C. Serum ACTH Rationale: Serum ACTH assays are very helpful in distinguishing the cause of Cushing’s syndrome. Patients with adrenal tumors have values approaching zero. Patients with ectopic ACTH tumors have values greater than 200 pg/dL. Fifty percent of patients with Cushing’s disease have high 8 a.m. ACTH levels (between 100–200 pg/dL). The high-dose dexamethasone suppression test is also used.

Answer 275

A. Overnight low-dose dexamethasone suppression test

Answer 276

A. Cholesterol

Answer 277

B. Estradiol (E2)

Answer 278

D. Testosterone

Answer 279

A. Gastrin

Answer 280

C. Hirsutism

Answer 281

A. Acute toxicity

Answer 282

B. Chronic toxicity

Answer 283

D. Cigarette smokers Rationale: Heroin (diacetylmorphine), an abused drug, is a derivative of morphine. The morphine used in its synthesis is generally obtained from opium.

Answer 284

B. Morphine Rationale: Heroin (diacetylmorphine), an abused drug, is a derivative of morphine. The morphine used in its synthesis is generally obtained from opium.

Answer 285

B. Marijuana

Answer 286

D. Marijuana Rationale: Marijuana is stored in fatty tissue and is metabolized slowly. In persons who use marijuana several times per week, cannabinoids can be detected several weeks after last use. For chronic daily users, this extends to months after discontinuation.

Answer 287

B. Ecstacy

Answer 288

A. 0.5 to 1 hour

Answer 289

B. Cocaine Rationale: Cocaine is an abused drug and not available for therapeutic use. After absorption, cocaine in the blood is rapidly converted into ecgonine and benzoylecgonine.

Answer 290

C. Cocaine Rationale: COCAINE IS A CNS STIMULANT. CNS STIMULANTS ● Cocaine and its metabolite, benzoylecgonine, and amphetamines and methamphetamines CNS DEPRESSANTS ● Barbiturates; methaqualone; benzodiazepines including Valium; and oxycodone and other opiates, including morphine, heroin (which metabolizes to morphine), codeine (methylmorphine), and methadone HALLUCINOGENS OR PSYCHOACTIVES ● Cannabinoids and phencyclidine (PCP) ANTIDEPRESSANTS ● Lithium, tricyclic antidepressants

Answer 291

C. Whole blood Rationale: After absorption, lead is distributed into an active pool in the blood and soft tissue and a storage pool in bone, teeth, and hair. In blood, the majority is found in erythrocytes, with only minor quantities in plasma or serum. Lead is mainly excreted by the kidney; hence urine or whole blood would be appropriate specimens for determining lead exposure.

Answer 292

A. Arsenic Rationale: Toxins may BIND SULFHYDRYL GROUPS IN KERATIN FOUND IN HAIR AND FINGERNAILS

Answer 293

C. Cyanide overdose Rationale: The principal symptoms of cyanide overdose are tachypnea (initially), followed by respiratory depression and cyanosis, hypotension, convulsions, and coma. Death may occur in a matter of minutes because cyanide is a fast-acting toxin. Diagnosis may be difficult, and a high index of suspicion is needed to make the correct diagnosis. Clues include the odor of bitter almonds, the occurrence of an altered mental status and tachypnea in the absence of cyanosis, and an unexplained metabolic acidosis (with an increased anion gap).

Answer 294

A. Arsenic toxicity

Answer 295

B. Ethanol Rationale: Ethanol is probably the most common drug of abuse and is frequently responsible for the presentation of patients with altered mental status to hospitals and emergency rooms.

Answer 296

C. Liberation, absorption, distribution, metabolism, excretion Rationale: LADME: Liberation, absorption, distribution, metabolism and excretion 1. Liberation is the release of the drug 2. Absorption is the transport of drug from the site of administration to the blood 3. Distribution refers to the delivery of the drug to the tissues 4. Metabolism is the process of chemical modification of the drug by cells 5. Excretion is the process by which the drug and its metabolites are removed from the body

Answer 297

A. Varies with the drug, depending on its rate of absorption Rationale: The peak concentration of a drug is the highest concentration obtained in the dosing interval. For oral drugs, the time of peak concentration is dependent upon their rates of absorption and elimination and is determined by serial blood measurements. Peak levels for oral drugs are usually drawn 1–2 hours after administration of the dose. For drugs given intravenously, peak levels are measured immediately after the infusion is completed.

Answer 298

C. Shortly before drug administration Rationale: When peak levels of the drug are required, the blood sample must be drawn at a specified time after drug administration. Trough levels are most reliably determined by collecting the blood sample before the next drug administration.

Answer 299

D. Intravenous Rationale: When a drug is administered intravenously, all the drug enters the bloodstream.

Answer 300

C. Salicylate

Answer 301

D. Liver Rationale: Paracetamol, also known as acetaminophen. Hepatotoxicity is common in acetaminophen overdose. It is particularly important to be able to determine the acetaminophen serum level rapidly so that the elimination half-life of the drug can be estimated. Hepatic necrosis is more common when the half-life exceeds 4 hours and is very likely when it exceeds 12 hours.

Answer 302

C. Tacrolimus Rationale: Tacrolimus (Prograf) is an antibiotic that functions as an immunosuppressant in organ transplantation, especially in liver transplants.

Answer 303

A. Theophylline Rationale: Theophylline is a bronchodilator that is used to treat asthma. The therapeutic range is 10-20 ug/mL, and use must be monitored to avoid toxicity. Use of theophylline has been replaced where possible with beta-adrenergic agonists, which are available in the inhaled form.

Answer 304

D. 3 and 4

Answer 305

B. Caffeine Rationale: Theophylline, a xanthine with bronchodilator activity, is widely used in the treatment of asthma. Because of its availability and potential toxicity, it can also be subject to accidental overdose. Chromatographic methods are effective in separating theophylline from caffeine and theobromine, which are two commonly occurring and potentially interfering xanthines. However, most clinical thin-layer chromatographic methods are relatively insensitive to the xanthines, and suspected theophylline overdose should be confirmed by HPLC or immunoassay methods.

Answer 306

B. Lithium Rationale: Lithium is used in the treatment of manic depression. Because of the small difference between therapeutic and toxic levels in the serum, accurate measurements of lithium concentrations are essential.

Answer 307

D. Vancomycin Rationale: The major toxicities of vancomycin are red man syndrome, nephrotoxicity, and ototoxicity. Red man syndrome is characterized by an erythemic flushing of the extremities. The renal and hearing effects are similar to those of the aminoglycosides.

Answer 308

B. Ethosuximide (Zarontin) Rationale: Ethosuximide is the drug of choice for absence (petit mal) seizures unaccompanied by other types of seizures. It is preferred over valproic acid, at least initially, because hepatotoxicity is a rare but serious side effect of valproic acid.

Answer 309

D. 1, 2 and 3 Rationale: Most analgesics, such as salicylates, acetaminophen, and ibuprofen, do not require TDM because physicians and pharmacists are able to achieve and maintain therapeutic levels with standardized dosing intervals. Because of the presumed safety of these medications, they are available without a prescription and sold as OVER-THE-COUNTER medications.

Answer 310

A. Glycosylated hemoglobin (HbA1c) Rationale: Long-term estimation of glucose concentration can be followed by measuring glycosylated hemoglobin (Hb A1c). A level of 8% or less is considered “good” glycemic control. Because the average red blood cell lives approximately 120 days, the glycosylated hemoglobin level at any one time reflects the average blood glucose level over the previous 2 to 3 months. Therefore, measuring the glycosylated hemoglobin provides the clinician with a time-averaged picture of the patient’s blood glucose concentration over the past 3 months.