(Chemistry) MLS Review Chapters 5.4-5.6 (Harr Ed.)
5.4 Which of the following assays has the poorest precision? Analyte:::::Mean (mmol/L):::::Standard Deviation A. Ca:::::2.5:::::0.3 B. K:::::4.0:::::0.4 C. Na:::::140:::::4.0 D. Cl:::::100:::::2.5 Formula: CV = s × 100/Mean.
A. Ca
5.4 Which of the following quality control (QC) rules would be broken 1 out of 20 times by chance alone? A. 1- 2s B. 2- 2s C. 1- 3s D. 1- 4s
A. 1- 2s
5.4 Given the following data, calculate the coefficient of variation for glucose. Analyte: Glucose Mean: 76 Standard Deviation: 2.3 Formula: % CV = s/mean x 100 A. 3.0% B. 4.6% C. 7.6% D. 33.0%
A. 3.0%
5.5 Which of the following formulas is the correct expression for creatinine clearance? A. Creatinine clearance = U/P X V X 1.73/A B. Creatinine clearance = P/V X U X A/1.73 C. Creatinine clearance = P/V X U X 1.73/A D. Creatinine clearance = U/V X P X 1.73/A
A. Creatinine clearance = U/P X V X 1.73/A
5.5 Which of the following statements is true? A. Cystatin C is measured immunochemically B. The calibrator used for cystatin C is traceable to the National Bureau of Standards calibrator C. Cystatin C assays have a lower coefficient of variation than plasma creatinine D. Enzymatic and rate Jaffe reactions for creatinine give comparable results
A. Cystatin C is measured immunochemically
5.6 Hyperalbuminemia is caused by: A. Dehydration syndromes B. Liver disease C. Burns D. Gastroenteropathy
A. Dehydration syndromes
5.4 A trend in QC results is most likely caused by: A. Deterioration of the reagent B. Miscalibration of the instrument C. Improper dilution of standards D. Electronic noise
A. Deterioration of the reagent
5.4 What measurement in addition to true negatives and prevalence is required to calculate the predictive value of a negative test result (PV-)? A. False negatives B. Variance C. True positives D. False positives
A. False negatives
5.5 Which of the following conditions is classified as a renal-type aminoaciduria? A. Fanconi syndrome B. Wilson's disease C. Hepatitis D. Homocystinuria
A. Fanconi syndrome
5.5 Orders for uric acid are legitimate stat requests because: A. Levels above 10 mg/dL cause urinary tract calculi B. Uric acid is hepatotoxic C. High levels induce aplastic anemia D. High levels cause joint pain
A. Levels above 10 mg/dL cause urinary tract calculi
5.4 Which of the following plots is best for detecting all types of QC errors? A. Levy-Jennings B. Tonks-Youden C. Cusum D. Linear regression
A. Levy-Jennings
5.6 High serum total protein but low albumin is usually seen in: A. Multiple myeloma B. Hepatic cirrhosis C. Glomerulonephritis D. Nephrotic syndrome
A. Multiple myeloma
5.5 Creatinine is formed from the: A. Oxidation of creatine B. Oxidation of protein C. Deamination of dibasic amino acids D. Metabolism of purines
A. Oxidation of creatine
5.5 Which enzyme deficiency is responsible for phenylketonuria (PKU)? A. Phenylalanine hydroxylase B. Tyrosine transaminase C. p-Hydroxyphenylpyruvic acid oxidase D. Homogentisic acid oxidase
A. Phenylalanine hydroxylase
5.4 One of two controls within a run is above +2s and the other control is below -2s from the mean. What do these results indicate? A. Poor precision has led to random error (RE) B. A systematic error (SE) is present C. Proportional error is present D. QC material is contaminated
A. Poor precision has led to random error (RE)
5.4 In most circumstances, when two controls within a run are both greater than ±2s from the mean, what action should be taken first? A. Recalibrate, then repeat controls followed by selected patient samples if quality control is acceptable B. Repeat the controls before taking any corrective action C. Change the reagent lot, then recalibrate D. Prepare fresh standards and recalibrate
A. Recalibrate, then repeat controls followed by selected patient samples if quality control is acceptable
5.5 Which of the following conditions is associated with hyperuricemia? A. Renal failure B. Chronic liver disease C. Xanthine oxidase deficiency D. Paget's disease of the bone
A. Renal failure
5.4 Referring to the Levy-Jennings chart, what analytical error is present during the second half of the month? A. Shift B. Trend C. Random error D. Kurtosis
A. Shift
5.4 Which of the following statistical tests is used to compare the means of two methods? A. Student's t test B. F distribution C. Correlation coefficient (r) D. Linear regression analysis
A. Student's t test
5.5 Of the methods used to measure amino acids, which is capable of measuring fatty acids simultaneously? A. Tandem-mass spectroscopy B. High-performance liquid chromatography C. Capillary electrophoresis D. Two-dimensional thin-layer chromatography
A. Tandem-mass spectroscopy
5.4 When referring to quality control (QC) results, what parameter usually determines the acceptable range? A. The 95% confidence interval for the mean B. The range that includes 50% of the results C. The central 68% of results D. The range encompassed by ±2.5 standard deviations
A. The 95% confidence interval for the mean
5.5 Urea is produced from: A. The catabolism of proteins and amino acids B. Oxidation of purines C. Oxidation of pyrimidines D. The breakdown of complex carbohydrates
A. The catabolism of proteins and amino acids
5.6 Which of the following factors is most likely to cause a falsely low result when using the BCG dye-binding assay for albumin? A. The presence of penicillin B. An incubation time of 120 seconds C. The presence of bilirubin D. Lipemia
A. The presence of penicillin
5.4 Serum samples collected from hospitalized patients over a 2-week period are split into two aliquots and analyzed for prostate specific antigen (PSA) by two methods. Each sample was assayed by both methods within 30 minutes of collection by a technologist familiar with both methods. The reference method is method × (upper reference limit = 4.0 μg/L). Linear regression analysis was performed by the least-squares method, and results are as follows: Linear Correlation Standard Error of Regression Coefficient (r) Estimate (S- y/x) Which statement best characterizes the relationship between the methods? A. There is a significant bias caused by constant error B. There is a significant proportional error C. There is no disagreement between the methods because the correlation coefficient approaches 1.0 D. There is no systematic error, but the random error of the new method is unacceptable
A. There is a significant bias caused by constant error
5.4 Two freezing point osmometers are compared by running 40 paired patient samples one time on each instrument, and the following results are obtained: Instrument Mean Standard Deviation Osmometer A 280 mOsm/kg 3.1 Osmometer B 294 mOsm/kg 2.8 If the critical value for F = 2.8, then what conclusion can be drawn regarding the precision of the two instruments? A. There is no statistically significant difference in precision B. Osmometer A demonstrates better precision that is statistically significant C. Osmometer B demonstrates better precision that is statistically significant D. Precision cannot be evaluated statistically when single measurements are made on samples
A. There is no statistically significant difference in precision
5.6 Which of the following statements regarding proteins is true? A. Total protein and albumin are about 10% higher in ambulatory patients B. Plasma total protein is about 20% higher than serum levels C. Albumin normally accounts for about one-third of the cerebrospinal fluid total protein D. Transudative serous fluid protein is about two-thirds of the serum total protein
A. Total protein and albumin are about 10% higher in ambulatory patient
5.4 Which of the following conditions is cause for rejecting an analytical run? A. Two consecutive controls greater than 2 s above or below the mean B. Three consecutive controls greater than 1 s above the mean C. Four controls steadily increasing in value but less than ±1 s from the mean D. One control above +1 s and the other below -1 s from the mean
A. Two consecutive controls greater than 2 s above or below the mean
5.5 Which uric acid method is associated with negative bias caused by reducing agents? A. Uricase coupled to the Trinder reaction B. Ultraviolet uricase reaction coupled to catalase and alcohol dehydrogenase reactions C. Measurement of the rate of absorbance decrease at 290 nm after addition of uricase D. Phosphotungstic acid using a protein-free filtrate
A. Uricase coupled to the Trinder reaction
5.5 Which analyte should be reported as a ratio using creatinine concentration as a reference? A. Urinary microalbumin B. Urinary estriol C. Urinary sodium D. Urinary urea
A. Urinary microalbumin
5.5 Enzymatic measurement of ammonia requires which of the following substrates and coenzymes? Substrate:::::Coenzyme A. a-ketogluturate:::::NADH B. Glutamate:::::NADH C. Glutamine:::::ATP D. Glutamine:::::NAD+
A. a-ketogluturate:::::NADH
5.4 What is the pH of a solution of HNO3, if the hydrogen ion concentration is 2.5 × 10-2 M? Formula: pH = -Log H+ A. 1.0 B. 1.6 C. 2.5 D. 2.8
B. 1.6
5.4 A glycerol kinase method for triglyceride calls for a serum blank in which normal saline is substituted for lipase in order to measure endogenous glycerol. Given the following results, and assuming the same volume of sample and reagent are used for each test, calculate the triglyceride concentration in the patient's sample. Standard of Concentration: 125 mg/dL Absorbance of Reagent Blank: 0.00 Absorbance of Standard: 0.62 Absorbance of Patient Serum: 0.750 Absorbance of Serum Blank: 0.100 Formula: Cu = [(Au - ASB)/As] × Cs Calculation: (0.750-0.100)/0.620 × 125 mg/dL= A. 119 mg/dL B. 131 mg/dL C. 156 mg/dL D. 180 mg/dL
B. 131 mg/dL
5.4 A procedure for cholesterol is calibrated with a serum-based cholesterol standard that was determined by the Abell-Kendall method to be 200.0 mg/dL. Assuming the same volume of sample and reagent are used, calculate the cholesterol concentration in the patient's sample from the following results: Standard Concentration: 200 mg/dL Absorbance of Reagent Blank: 0.00 Absorbance of Standard: 0.860 Absorbance of Patient Serum: 0.740 Formula: Cu = Au/As × Cs Calculation: Cu = 0.740/0.860 × 200 mg/dL = _____ A. 123 mg/dL B. 172 mg/dL C. 232 mg/dL D. 314 mg/dL
B. 172 mg/dL
5.4 How many significant figures should be reported when the pH of a 0.060 M solution of nitric acid is calculated? A. 1 B. 2 C. 3 D. 4
B. 2
5.5 Urea concentration is calculated from the BUN by multiplying by a factor of: A. 0.5 B. 2.14 C. 6.45 D. 14
B. 2.14
5.4 What is the pH of a buffer containing 40.0 mmol/L NaHC2O4 and 4.0 mmol/L H2C2O4? (pKa = 1.25) Formula: pH = pKa + log salt _____ Acid Calculation: = 1.25 + log 40.0 mmol/L -------------- 4.0 mmol/L = 1.25 + log 10=___________ A. 1.35 B. 2.25 C. 5.75 D. 6.12
B. 2.25
5.4 A solvent needed for HPLC requires a 20.0 mmol/L phosphoric acid buffer, pH 3.50, made by mixing KH2PO4 and H3PO4. How many grams of KH2PO4 are required to make 1.0 L of this buffer? Formula weights: KH2PO4 = 136.1; H3PO4 = 98.0;pKa H3PO4 = 2.12 Formula: pH = pKa + log(salt/acid) First Calculation: 3.50 = 2.12 + log(KH2PO4/H3PO4) 1.38 = log(KH2PO4/H3PO4) antilog 1.38 = KH2PO4/H3PO4 KH2PO4/H3PO4 = _________ Then: H3PO4 + (answer from above × H3PO4) = 20.0 mmol/L 24.99 × H3PO4 = 20.0 mmol/L H3PO4 = 20.0/24.99 = 0.800 mmol/L KH2PO4 = 20.0-0.800 = _____________ Then: Answer from above × 136.1 g/mol = _________ A. 1.96 g B. 2.61 g C. 2.72 g D. 19.2 g
B. 2.61
5.4 What is the pH of a 0.05 M solution of acetic acid? Ka = 1.75 × 10-5, pKa = 4.76 Formula: pH = 1/2 (pKa - Log HA) Calculation: pH = 1/2 (4.76 - Log 5.0 × 10-2) 1/2 (4.76 + 1.30) = _________ A. 1.7 B. 3.0 C. 4.3 D. 4.6
B. 3.0
5.4 The following plot represents a study of a screening test for malignant prostate cancer using plasma PSA (ng/mL). The outcome measured was positive cytology results obtained by biopsy. What concentration gives the highest sensitivity with the least number of unnecessary biopsies? A. 2.6 B. 3.6 C. 3.8 D. 5.2
B. 3.6
5.4 How many milliliters of a 2,000.0 mg/dL glucose stock solution are needed to prepare 100.0 mL of a 150.0 mg/dL glucose working standard? Formula: C1 × V1 = C2 × V2 Calcualtion: 2000.0 mg/dL × V1 = 150.0 mg/dL × 100.0 mL V1 = (150.0 ÷ 2000.0) × 100.0 mL V1 = ________ A. 1.5 mL B. 7.5 mL C. 15.0 mL D. 25.0 mL
B. 7.5 mL
5.6 Which of the following dyes is the most specific for measurement of albumin? A. Bromcresol green (BCG) B. Bromcresol purple (BCP) C. Tetrabromosulfophthalein D. Tetrabromphenol blue
B. Bromcresol purple (BCP)
5.5 Uric acid is derived from the: A. Oxidation of proteins B. Catabolism of purines C. Oxidation of pyrimidines D. Reduction of catecholamines
B. Catabolism of purines
5.6 Upon which principle is the biuret method based? A. The reaction of phenolic groups with CuIISO4 B. Coordinate bonds between Cu+2 and carbonyl and imine groups of peptide bonds. C. The protein error of indicator effect producing color when dyes bind protein D. The reaction of phosphomolybdic acid with protein
B. Coordinate bonds between Cu+2 and carbonyl and imine groups of peptide bonds.
5.5 What substance may be measured as an alternative to creatinine for evaluating GFR? A. Plasma urea B. Cystatin C C. Uric acid D. Potassium
B. Cystatin C
5.4 What is the first day in the second half of the month that patient results would be rejected? A. Day 16 B. Day 17 C. Day 18 D. Day 19
B. Day 17
5.4 When establishing QC limits, which of the following practices is inappropriate? A. Using last month's QC data to determine current target limits B. Exclusion of any QC results greater than ±2s from the mean C. Using control results from all shifts on which the assay is performed D. Using limits determined by reference laboratories using the same method
B. Exclusion of any QC results greater than ±2s from the mean
5.6 Which of the following protein methods has the highest analytical sensitivity? A. Refractometry B. Folin-Lowry C. Turbidimetry D. Direct ultraviolet absorption
B. Folin-Lowry
5.5 In the ultraviolet enzymatic method for BUN, the urease reaction is coupled to a second enzymatic reaction using: A. AST B. Glutamate dehydrogenase C. Glutamine synthetase D. Alanine aminotransferase (ALT)
B. Glutamate dehydrogenase
5.5 Which statement regarding creatinine is true? A. Serum levels are elevated in early renal disease B. High serum levels result from reduced glomerular filtration C. Serum creatine has the same diagnostic utility as serum creatinine D. Serum creatinine is a more sensitive measure of renal function than creatinine clearance
B. High serum levels result from reduced glomerular filtration
5.5 Creatinine is considered the substance of choice to measure endogenous renal clearance because: A. The rate of formation per day is independent of body size B. It is completely filtered by the glomeruli C. Plasma levels are highly dependent upon diet D. Clearance is the same for both men and women
B. It is completely filtered by the glomeruli
5.4 A laboratory is establishing a reference range for a new analyte and wants the range to be determined by the regional population of adults age 18 and older. The analyte concentration is known to be independent of race and gender. Which is the most appropriate process to follow? A. Determine the mean and standard deviation of the analyte from 40 healthy adults and calculate the ±2s limit B. Measure the analyte in 120 healthy adults and calculate the central 95th percentile C. Measure the analyte in 120 healthy adults and use the lowest and highest as the reference range limits D. Measure the analyte in 60 healthy adults and 60 adults with conditions that affect the analyte concentration; calculate the concentration of least overlap
B. Measure the analyte in 120 healthy adults and calculate the central 95th percentile
5.4 When the magnitude of error increases with increasing sample concentration, it is called: A. Constant error B. Proportional error C. Random error D. Bias
B. Proportional error
5.5 Select the primary reagent used in the Jaffe method for creatinine. A. Alkaline copper II sulfate B. Saturated picric acid and NaOH C. Sodium nitroprusside and phenol D. Phosphotungstic acid
B. Saturated picric acid and NaOH
5.5 The modification of diet in renal disease (MDRD) formula for calculating eGFR requires which four parameters? A. Urine creatinine, serum creatinine, height, weight B. Serum creatinine, age, gender, race C. Serum creatinine, height, weight, age D. Urine creatinine, gender, weight, age
B. Serum creatinine, age, gender, race
5.4 Which of the following total quality management tools can be used to calculate the analytical error rate for an analyte in the clinical laboratory? A. LEAN B. Six sigma C. ISO 9000 D. Laboratory information system
B. Six sigma
5.5 BUN is determined electrochemically by coupling the urease reaction to measurement of: A. Potential with a urea-selective electrode B. The timed rate of increase in conductivity C. The oxidation of ammonia D. Carbon dioxide
B. The timed rate of increase in conductivity
5.4 Which statement best summarizes the relationship between the new BUN method and reference method based upon the following linear regression scatterplot? A. The methods agree very well but show a high standard error of estimate B. There is little or no constant error, but some proportional error C. There will be a significant degree of uncertainty in the regression equation D. There is significant constant and proportional error but little random error
B. There is little or no constant error, but some proportional error
5.4 Which of the following plots is best for comparison of precision and accuracy among laboratories? A. Levy-Jennings B. Tonks-Youden C. Cusum D. Linear regression
B. Tonks-Youden
5.4 Examine the Levy-Jennings chart at the bottom of the answer and identify the QC problem that occurred during the first half of the month: A. Shift B. Trend C. Random error D. Kurtosis
B. Trend
5.4 The term R-4S means that: A. Four consecutive controls are greater than ±1 standard deviation from the mean B. Two controls in the same run are greater than 4s units apart C. Two consecutive controls in the same run are each greater than ±4s from the mean D. There is a shift above the mean for four consecutive controls
B. Two controls in the same run are greater than 4s units apart
5.4 A new method for BUN is evaluated by comparing the results of 40 paired patient samples to the urease-UV method. Normal and high controls were run on each shift for 5 days, five times per day. The results are as follows: Linear Regression: y =0.3 + 0.90x Low Control: x= 14.2 mg/dL s= 1.24 High Control= x= 48.6 mg/dL s= 1.12 What is the total analytical error estimate for a sample having a concentration of 50 mg/dL? Linear regression analysis gives an estimate of SE, which is equal to (ŷ - xc) where xc is the expected concentration, and ŷ is the value predicted by the linear regression equation. SE = [-0.3 + (0.9 × 50 mg/dL)] - 50.0 mg/dL = 44.7-50.0 = -5.3 mg/dL The standard deviation of the new method for the high control is used to estimate the RE because the mean of this control is nearest to the expected concentration of 50 mg/dL. RE is estimated by ±1.96 × s. RE = 1.96 × 1.12 = ± 2.2 mg/dL Total analytical error (TE) is equal to the sum of SE and RE. TE = SE + RE = -5.3 mg/dL + (-2.2 mg/dL) = -7.5 mg/dL A. -2.2 mg/dL B. -2.8 mg/dL C. -7.5 mg/dL D. -10.0 mg/dL
C. -7.5 mg/dL
5.4 How many milliliters of HNO3 (purity 68.0%, specific gravity 1.42) are needed to prepare 1.0 L of a 2.0 N solution? Atomic weights: H = 1.0; N = 14.0; O = 16.0 Calculation: mL HNO3 = 126.0 g ÷ 0.9656 g/mL =126.0 g × 1.0 mL/0.9656 g = _________ A. 89.5 mL B. 126.0 mL C. 130.5 mL D. 180.0 mL
C. 130.5 mL
5.4 A biuret reagent requires preparation of a stock solution containing 9.6 g of copper II sulfate (CuSO4) per liter. How many grams of CuSO4 • 5H2O are needed to prepare 1.0 L of the stock solution? Atomic weights: H = 1.0; Cu = 63.6; O = 16.0; S = 32.1 First Calculation: 5H2O × 100 = (159.7 ÷ 249.7) × 100 = ______ Then: Grams CuSO4 • 5H2O = 9.6 g ÷ decimal form of % you got above = _______ A. 5.4 g B. 6.1 g C. 15.0 g D. 17.0 g
C. 15.0 g
5.4 Convert 2.0 mEq/L magnesium (atomic weight = 24.3) to milligrams per deciliter. First Calculation: Milliequivalent weight Mg Milliequivalent weight Mg = 24.3 ÷ 2 = ____________ Then: 2.0 mEq/L × 12.15 mg/mEq = ________ Then: 24.3 mg/L × 1.0 L/10.0 dL = _________ A. 0.8 mg/dL B. 1.2 mg/dL C. 2.4 mg/dL D. 4.9 mg/dL
C. 2.4 mg/dL
5.4 Convert 10.0 mg/dL calcium (atomic weight = 40.1) to International System of Units (SI). First Calculation: 10.0 mg/dL × 10.0 dL/1.0 L = ______ Then: 100.0 mg/L × 1.0 mmol/40.1 mg = _______ A. 0.25 B. 0.40 C. 2.5 D. 0.4
C. 2.5
5.4 How many grams of sodium hydroxide (NaOH) are required to prepare 150.0 mL of a 5.0% w/v solution? Calculation: (5.0 g × 150.0 mL) ÷ 100.0 mL = _______ A. 1.5 g B. 4.0 g C. 7.5 g D. 15.0 g
C. 7.5 g
5.4 A new tumor marker for ovarian cancer is evaluated for sensitivity by testing serum samples from patients who have been diagnosed by staging biopsy as having malignant or benign lesions. The following results were obtained: Number of malignant patients who are positive for: CA 125 = 21 out of 24 Number of benign patients who are negative for: CA 125 = 61 out of 62 What is the sensitivity of the new CA 125 test? Formula: % Sensitivity = TP × 100 ----------- TP + FN Calculation: Sensitivity = (21 × 100) ÷ (21 + 3) = ___________ A. 98.4% B. 95.3% C. 87.5% D. 85.0%
C. 87.5%
5.4 Calculate the pH of a solution of 1.5 × 10-5 M NH4OH. Formula: pOH = -Log [OH-] Calculation: pOH = - Log 1.5 x 10-5 = ______ pH = 14 - pOH pH = 14 - answer from above = ________ A. 4.2 B. 7.2 C. 9.2 D. 11.2
C. 9.2
5.4 In which circumstances is a validation study (versus performing routine quality control) required? A. Instrument recalibration B. Source lamp or ion selective electrode change C. Change in reagent lot D. Change in calibrator lot
C. Change in reagent lot
5.5 In addition to phenylketonuria, maple syrup urine disease, and homocystinuria, what other aminoaciduria can be detected by tandem MS? A. Alkaptonuria B. Hartnup disease C. Citrullinemia D. Cystinuria
C. Citrullinemia
5.4 Which of the following plots will give the earliest indication of a shift or trend? A. Levy-Jennings B. Tonks-Youden C. Cusum D. Histogram
C. Cusum
5.4 Referring to the Levy-Jennings chart, what is the first day in the month when the run should be rejected and patient results should be repeated? A. Day 6 B. Day 7 C. Day 8 D. Day 9
C. Day 8
5.4 Which of the following methods is most useful in order to detect sample misidentification? A. Cumulative summation B. Critical limit C. Delta limit D. Significant change limit
C. Delta limit
5.5 Blood ammonia levels are usually measured in order to evaluate: A. Renal failure B. Acid-base status C. Hepatic coma D. Gastrointestinal malabsorption
C. Hepatic coma
5.5 Which statement about ammonia is true? A. Normally, most of the plasma ammonia is derived from peripheral blood deamination of amino acids B. Ammonia-induced coma can result from salicylate poisoning C. Hepatic coma can result from Reye's syndrome D. High plasma ammonia is usually caused by respiratory alkalosis
C. Hepatic coma can result from Reye's syndrome
5.5 Interference from other reducing substances can be partially eliminated in the Jaffe reaction by: A. Measuring the product at 340 nm B. Measuring the product with an electrode C. Measuring the timed rate of product formation D. Performing a sample blank
C. Measuring the timed rate of product formation
5.5 Urinary urea measurements may be used for calculation of: A. Glomerular filtration B. Renal blood flow C. Nitrogen balance D. All of these options
C. Nitrogen balance
5.6 Which statement about the biuret reaction for total protein is true? A. It is sensitive to protein levels below 0.1 mg/dL B. It is suitable for urine, exudates, and transudates C. Polypeptides and compounds with repeating imine groups react D. Hemolysis will not interfere
C. Polypeptides and compounds with repeating imine groups react
5.5 In which case would eGFR derived from the plasma creatinine likely give a more accurate measure of GFR than measurement of plasma cystatin C? A. Diabetic patient B. Chronic renal failure C. Post-renal transplant D. Chronic hepatitis
C. Post-renal transplant
5.5 A patient's BUN is 60 mg/dL and serum creatinine is 3.0 mg/dL. These results suggest: A. Laboratory error measuring BUN B. Renal failure C. Prerenal failure D. Patient was not fasting
C. Prerenal failure
5.5 Which of the following enzymes allows creatinine to be measured by coupling the creatinine amidohydrolase (creatininase) reaction to the peroxidase reaction? A. Glucose-6-phosphate dehydrogenase B. Creatinine iminohydrolase C. Sarcosine oxidase D. Creatine kinase
C. Sarcosine oxidase
5.6 Kjeldahl's procedure for total protein is based upon the premise that: A. Proteins are negatively charged B. The pKa of proteins is the same C. The nitrogen content of proteins is constant D. Proteins have similar tyrosine and tryptophan content
C. The nitrogen content of proteins is constant
5.4 What is the minimum requirement for performing QC for a total protein assay? A. One level assayed every 8 hours B. Two levels assayed within 8 hours C. Two levels assayed within 24 hours D. Three levels assayed within 24 hours
C. Two levels assayed within 24 hours
5.4 Two methods for total cholesterol are compared by running 40 paired patient samples in duplicate on each instrument. The following results are obtained: Instrument Mean Standard Deviation Method x (reference 235 mg/dL 3.8 method) Method y (candidate 246 mg/dL 3.4 method) Assuming the samples are collected and stored in the same way and the analysis done by a technologist who is familiar with both methods, what is the bias of method y? (The bias is defined as the difference between the means of the two methods and is calculated using the formula: bias = y - x. ) A. 0.4 B. 7.2 C. 10.6 D. 11.0
D. 11.0
5.4 A procedure for aspartate aminotransferase (AST) is performed manually because of a repeating error code for nonlinearity obtained on the laboratory's automated chemistry analyzer; 0.05 mL of serum and 1.0 mL of substrate are used. The reaction rate is measured at 30°C at 340 nm using a 1.0 cM light path, and the delta absorbance (-ΔA) per minute is determined to be 0.382. Based upon a molar absorptivity coefficient for NADH at 340 nm of 6.22 X 103 M-1 cM-1 L-1, calculate the enzyme activity in international units (IUs) per liter. Formula: IU/L = ΔA/min x TV(mL) × 1,000 mL/L ---------------------------------- 6.22(A/μmol/mL/cM) x 1 cm x SV(mL) Calculation: = ΔA/min × 1.05 x 1,000 ------------------------ 6.22 X 0.05 = ΔA/min × 1,050 ---------------- 0.311 = ΔA/min × 3,376 0.382 × 3376 = ________ A. 26 IU/L B. 326 IU/L C. 1228 IU/L D. 1290 IU/L
D. 1290 IU/L
5.4 A new test for prostate cancer is found to have a sensitivity of 80.0% and a specificity of 84.0%. If the prevalence of prostate cancer is 4.0% in men over 42 years old, what is the predictive value of a positive test result (PV+) in this group? A. 96.0% B. 86.0% C. 32.4% D. 17.2%
D. 17.2%
5.4 Two consecutive controls are both beyond -2s from the mean. How frequently would this occur on the basis of chance alone? A. 1:100 B. 5:100 C. 1:400 D. 1:1,600
D. 1:1,600
5.4 How many milliliters of glacial acetic acid are needed to prepare 2.0 L of 10.0% v/v acetic acid? Calculation: (10.0 mL × 2000.0 mL) ÷ 100.0 mL = __________ A. 10.0 mL B. 20.0 mL C. 100.0 mL D. 200.0 mL
D. 200.0 mL
5.4 All of the following are requirements for a QC material except: A. Long-term stability B. The matrix is similar to the specimens being tested C. The concentration of analytes reflects the clinical range D. Analyte concentration must be independent of the method of assay
D. Analyte concentration must be independent of the method of assay
5.5 Which of the statements below about serum urea is true? A. Levels are independent of diet B. Urea is not reabsorbed by the renal tubules C. High BUN levels can result from necrotic liver disease D. BUN is elevated in prerenal as well as renal failure
D. BUN is elevated in prerenal as well as renal failure
5.4 Given the following QC chart, identify the day in which a violation of the R-4s QC rule occurs. A. Day 3 B. Day 8 C. Day 10 D. Day 15
D. Day 15
5.4 In addition to the number of true negatives (TN), which of the following measurements is needed to calculate specificity? A. True positives B. Prevalence C. False negatives D. False positives
D. False positives
5.6 Which of the following conditions is most commonly associated with an elevated level of total protein? A. Glomerular disease B. Starvation C. Liver failure D. Malignancy
D. Malignancy
5.5 Which aminoaciduria results in the overflow of branched chain amino acids? A. Hartnup's disease B. Alkaptonuria C. Homocystinuria D. Maple syrup urine disease
D. Maple syrup urine disease
5.5 Which product is measured in the coupling step of the urease-UV method for BUN? A. CO2 B. Dinitrophenylhydrazine C. Diphenylcarbazone D. NAD+
D. NAD+
5.4 When comparing the laboratory's monthly mean to its peer group to determine if bias is present, what statistic is most appropriate? A. F test B. Linear regression analysis C. Correlation coefficient D. Standard deviation index
D. Standard deviation index
5.5 SITUATION: A sample for ammonia assay is taken from an IV line that had been capped and injected with lithium heparin (called a heparin lock). The sample is drawn in a syringe containing lithium heparin, and immediately capped and iced. The plasma is separated and analyzed within 20 minutes of collection, and the result is 50 μg/dL higher than one measured 4 hours before. What is the most likely explanation of these results? A. Significantly greater physiological variation is seen with patients having systemic, hepatic, and gastrointestinal diseases B. The syringe was contaminated with ammonia C. One of the two samples was collected from the wrong patient D. Stasis of blood in the line caused increased ammonia
D. Stasis of blood in the line caused increased ammonia
5.5 A sample of amniotic fluid collected for fetal lung maturity studies from a woman with a pregnancy compromised by hemolytic disease of the newborn (HDN) has a creatinine of 88 mg/dL. What is the most likely cause of this result? A. The specimen is contaminated with blood B. Bilirubin has interfered with the measurement of creatinine C. A random error occurred when the absorbance signal was being processed by the analyzer D. The fluid is urine from accidental puncture of the urinary bladder
D. The fluid is urine from accidental puncture of the urinary bladder
5.4 Which explanation is the best interpretation of the following BUN bias plot? A. The new method consistently overestimates the BUN by a constant concentration B. The new method is greater than the reference method but not by a statistically significant margin C. The new method is lower than the reference method by 5 mg/dL D. The new method is lower than the reference and the magnitude is concentration dependent
D. The new method is lower than the reference and the magnitude is concentration dependent
5.5 Which of the following conditions is most likely to cause a falsely high creatinine clearance result? A. The patient uses the midstream void procedure when collecting his or her urine B. The patient adds tap water to the urine container because he or she forgets to save one of the urine samples C. The patient does not empty his or her bladder at the conclusion of the test D. The patient empties his or her bladder at the start of the test and adds the urine to the collection
D. The patient empties his or her bladder at the start of the test and adds the urine to the collection
