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30 Cards in this Set
- Front
- Back
A 52-year-old man with a history of alcohol abuse presents with sudden severe abdominal pain
associated with nausea and vomiting. Which of the following is true when considering serum testing for acute pancreatitis? A. Elevated amylase levels appear well before elevated lipase levels. B. Elevated amylase is more specific than elevated lipase for pancreatitis. C. Elevated lipase is more specific than elevated amylase for pancreatitis D. Elevated Amylase and elevated lipase are equally specific for pancreatitis E. Lipase has both salivary and pancreatic isoforms, which reduces specificity. |
C
While lipase and amylase are both elevated in cases of acute pancreatitis, amylase is less specific to pancreatitis. In acute pancreatitis elevated lipase and amylase levels occur at approximately the same time (amylase within 5 to 8 hours after symptom onset, lipase within 4 to 8 hours after symptom onset). A number of causes of elevated serum amylase have been observed. These include elevations of the salivary amylase isoform due to salivary gland lesions or increases in the pancreatic isoform in cases of biliary tract disease or appendicitis. |
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Macroamylase refers to:
A. The presence of complexes consisting of amylase and immunglobulins that result in elevated amylase levels. B. The elevation of serum salivary amylase isoform in cases of ectopic pregnancy or ovarian malignancy. C. The presence of elevated serum amylase levels in acute pancreatitis D. The false elevation of amylase levels in lipemic specimens. E. The elevation of amylase levels in cases of biliary tract obstruction. |
A
Macroamylases are complexes between IgG or IgG and amylase. These large complexes are not excreted by the kidneys. This asymptomatic phenomenon can result in a large increase in measured amylase concentrations |
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A 63-year-old woman with weight loss is found to have a slightly elevated alanine
aminotransferase level of 45 U/L (N=8-33 U/L) and an elevated aspartate aminotransferase level of 150 U/L (N=4-36 U/L) Which of the following is the most likely cause? A. Acute Viral Hepatitis B. Reye’s Syndrome C. Acute Alcoholic Hepatitis D. Acute Mononucleosis E. Chronic Viral Hepatitis |
C
Although AST may be briefly higher initially in some forms of acute injury, ALT is generally higher than AST in most forms of acute and chronic hepatic injury. However in alcoholic hepatitis AST is greater than ALT in alcoholic hepatitis. An AST/ALT ratio of 2:1 or greater is suggestive of that diagnosis. |
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A 33-year-old jaundiced man is found to have the following serum laboratory values: Total
Bilirubin of 3.0 mg/dL (normal <1.0), Direct bilirubin of 2.7 mg/dL (normal <0.2). Which of the following is the most likely cause? A. Gilberts Syndrome B. Fasting C. Crigler-Najjar syndrome D. Bile Duct Obstruction E. Hemolytic Anemia |
D
Of the choices presented Gilberts Syndrome and Crigler-Najjar syndrome lead to increases in unconjugated bilirubin (indirect). A larger increase in unconjugated bilirubin would also be expected in cases of hemolysis. Although Dubin-Johnson and Rotor syndrome also lead to isolated elevation in conjugated bilirubin bile duct obstruction is the only plausible choice in this question. |
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A 53-year-old woman presents with chronic intermittent acute abdominal pain that is determined to
stem from common bile duct obstruction. Which of the following liver function markers would one not expect to be highly elevated in the serum? A. Gamma-glutamyltransferase B. Total Bilirubin C. Alkaline Phosphatase D. Aspartate Aminotransferase E. Conjugated Bilirubin |
D
Unlike the other markers, AST is not generally dramatically elevated in bile duct obstruction. Although there may occasionally be an acute increase in ALT and AST serum concentrations in cases of gallstones and other obstructions, ALT and AST levels fall and return to normal in 8 to 10 days. |
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Which of the following is the most specific serum marker for alcohol dependency?
A. Carbohydrate Deficient Transferrin B. Lipase C. Gamma-Glutamyl Transferase D. AFP-L3% E. Lactate Dehydrogenase |
A
Both GGT and CDT are markers of sustained alcohol consumption. CDT is the most specific marker of chronic alcohol abuse to date and consists of asialo transferrin isoforms. A number of factors can elevate GGT. Carbohydrate-deficient transferrin (CDT) is often used for diagnosis of chronic alcohol abuse. |
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Warfarin metabolism is mainly performed by:
A. P450 CYP3A4 B. P450 CYP2C9 C. P450 CYP2D6 D. Thiopurine S-Methyltransferase (TPMT) E. N-Acetyl-Transferases (NATs) |
B
CYP3A4—Mediates most phase 1 biotransformation reactions. Example substrates include: erythromycin, benzodiazepines, immune suppressors (cyclosporine, FK506),HIV protease inhibitors, Calcium Channel blockers, and methadone. CYP2C9—Substrates include Warfarin, NSAIDs, Angiotensin II blockers CYP2D6—Mediates Many phase 1 biotransformation reactions. Substrates include: Beta blockers, antidepressants, antipsychotics, codeine. CYP2E1—Substrates include: Acetaminophen, Chlorzoxazone, Ethanol Thiopurine S-Methyltransferase (TPMT)—Substrates include azothioprine and 6-mercaptopurine |
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An active form of an antidepressant is subsequently oxidized by P450 CYP2C9. Which patients
would you generally expect to need the highest dose of antidepressants to maintain similar serum concentrations of active drug? A. Extensive metabolizers (EM) B. Intermediate Metabolizers (IM) C. Poor Metabolizers (PM) D. Ultrarapid metabolizers (UM) E. Females |
D
Ultra-rapid metabolizers would oxidize the active antidepressant most rapidly and increase the rate of removal of bioactive compound. The slowest to the most rapid metabolic phenotypes are: PM, IM, EM, and UM. |
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Which of the following is untrue in cases of toxic overdose of acetaminophen?
A. Depression of P450 enzyme activities by other therapeutic drugs result in the increased production of the toxic metabolite: N-acetyl-p-benzoquinone immine B. Glutathione depletion in alcoholics can lead to increased acetaminophen hepatotoxicity C. The Rumack-Matthew nomogram can be used to estimate the probability of hepatic toxicity if the time of ingestion and acetaminophen plasma concentration is known. D. Administration of N-acetylcystiene is a common antidotal therapy E. Children are generally not at risk of developing Reye’s syndrome. |
A
P450 enzyme activities may be increased by other therapeutic drugs and directly produce the toxic metabolite: N-acetyl-p-benzoquinoneimine. In the presence of glutathione this toxic intermediate is further metabolized through sulfate conjugation. Answers B-D are all true. For answer E, Reyes syndrome in children is associated with Salicylate ingestion, thus answer E is also true. |
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Which of the following is the most specific serum marker for alcohol dependency?
A. Carbohydrate Deficient Transferrin B. Lipase C. Gamma-Glutamyl Transferase D. AFP-L3% E. Lactate Dehydrogenase |
A
Both GGT and CDT are markers of sustained alcohol consumption. CDT is the most specific marker of chronic alcohol abuse to date and consists of asialo transferrin isoforms. A number of factors can elevate GGT. Carbohydrate-deficient transferrin (CDT) is often used for diagnosis of chronic alcohol abuse. |
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Which forms of the elements Arsenic (As) and Mercury (Hg) are considered to be the most toxic?
A. All Arsenic and Mercury compounds are highly toxic B. Inorganic Arsenic species such as As(III) and As(V), and inorganic Mercury species such as elemental mercury (Hg0) C. Organic Arsenic compounds such as arsenobetaine and arsenocholine, and organic Mercury compounds such as methyl Mercury (CH3Hg+) D. Organic Arsenic compounds and inorganic Mercury species E. Inorganic Arsenic species and organic Mercury compounds |
E. Inorganic arsenic species such as those found in groundwater are considered to be toxic while organic
arsenic compounds as found in some foods are generally nontoxic. Elemental mercury is relatively nontoxic, although it can be biotransformed into more toxic organic compounds within the body. Organic mercury compounds such as methyl mercury accumulate in the food chain and result in high mercury concentrations in some animals such as predatory fish. |
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Which of the following are often associated with Wilson’s disease?
I. Elevated ceruloplasm levels. II. The Presence of Kayser-Fleisher rings III. The Presence of Mees’ Lines IV. Increased Free Serum Copper V. Low Urine Serum copper A. all of the above B. I and V. C. II and IV. D. I, III and V. E. IV and V. |
Answer is C) Wilson’s disease is characterized by accumulation of excess copper. As copper is deposited in body
stores total serum copper is of limited utility. Free serum copper is typically elevated, but observed ceruloplasm concentrations are typically normal to slightly lowered. Excess urine copper is indicative of excess body copper burden and is a good screen for Wilson Disease. Other manifestations of Wilson disease are the appearance of Kayser- Fleischer rings in the eyes and elevated copper in liver biopsy. Mees lines are typically associated with excess lead levels. |
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Which of the following elements are found predominately in erythrocytes while in circulation?
A. Organic Mercury compounds. B. Cadmium C. Copper D. Lead E. B and D |
Answer is E): Circulating lead and cadmium are both found predominantly in erythrocytes. The majority of circulating
copper is found in the serum as it is predominantly bound to the serum protein ceruloplasmin. Aluminum also readily binds serum proteins. The majority (>70%) of both cadmium and lead segregates in the erythrocytes. |
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Which set of elements are all considered to be essential trace elements?
A. Selenium, Cobalt, Lead, Cadmium, Zinc, Iron, Nickel B. Mercury, Selenium, Zinc, Iron C. Molybdenum, Selenium, Zinc, Nickel D. Arsenic, Mercury, Iron, Nickle, Manganese E. Mercury, Cadmium, Lead, Cobalt |
Answer is C): The essential elements of which small amounts are needed to sustain normal function include: Iron,
Manganese, Molybdenum, Nickel, Selenium, and Zinc. Non-essential toxic elements include: Arsenic, Cadmium, Cobalt, Lead, and Mercury. Iron is not considered as a trace element by some as it is present in relatively much higher concentrations than the other elements listed here. |
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What is the most appropriate sample type for diagnosing suspected acute arsenic exposure in the previous 3 days.
A. Whole Blood B. Serum C. EDTA Plasma D. Urine E. Hair samples |
Answer D): The half life of arsenic in serum and whole blood is extremely brief with a half life of less than 6 hours as it
readily incorporates into the rest of the body. However, arsenic in urine can be observed for up to three weeks following exposure. As Arsenic avidly binds sulfhydryl groups which is abundant in keratin hair and nails can also be used to investigate exposure. In some cases early exposure can be substantiated by hair samples taken from the nape of the neck. However, hair samples can often be contaminated by external sources. |
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Suppose a hypothetical serum marker “factor X” was discovered to be elevated in cases hepatocellular carcinoma
(HCC). Two different plate-based ELISA tests for factor X were developed, test A and test B. Examine the ROC curve of the factor X concentration cutoffs (factor X concentration above which a sample is called positive), and determine the most effective test for the detection of HCC and the best “factor X” cutoff concentration. (See Image #1 on the website for this question set) A. 85 mg/L using Test A B. 100 mg/L using Test A C. 85 mg/L using Test B D. 100 mg/L using Test B |
Answer is C). 85 mg/L using test B. Test B has higher sensitivity and specificity for most Factor X cutoffs. 85 mg/L
gives a ~95% sensitivity with ~90% sensitivity, while 100 mg/dL yields ~98% sensitivity but only has 20% specificity. |
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Suppose a study was performed using a third assay for factor X on a group of 1500 individuals with elevated liver
enzymes. The prevalence of HCC was 10% in this population. Of the patients with confirmed HCC, 120 were identified as positive by this assay. Unfortunately 150 patients who did not have HCC were also classified as positive by factor X testing. What is the sensitivity (%) of this test? A. 10% B. 11% C. 80% D. 89% E. 90% |
Answer C). Of the 1500 individuals 150 have HCC. Of these 120 are True Positive and 30 are False Negative. Of the
1350 people without HCC 150 were False Positive and 1200 were True Negative. Since Sensitivity is TP/(TP+FN) the sensitivity = 0.8 or 80%. |
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Suppose a study was performed using a third assay for factor X on a group of 1500 individuals with elevated liver
enzymes. The prevalence of HCC was 10% in this population. Of the patients with confirmed HCC, 120 were identified as positive by this assay. Unfortunately 150 patients who did not have HCC were also classified as positive by factor X testing.What is the specificity (%) A. 10% B. 11% C. 80% D. 89% E. 90% |
Answer D): Of the 1500 individuals 150 have HCC. Of these 120 are True Positive and 30 are False Negative. Of the
1350 people without HCC 150 were False Positive and 1200 were True Negative. Since Specificity is TN/(TN+FP) the sensitivity = 0.888 or 89%. |
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Suppose a study was performed using a third assay for factor X on a group of 1500 individuals with elevated liver
enzymes. The prevalence of HCC was 10% in this population. Of the patients with confirmed HCC, 120 were identified as positive by this assay. Unfortunately 150 patients who did not have HCC were also classified as positive by factor X testing.What is the positive predictive value (%) A. 44% B. 40% C. 56% D. 15% E. 85% |
Answer A): Of the 1500 individuals 150 have HCC. Of these 120 are True Positive and 30 are False Negative. Of the
1350 people without HCC, 150 were False Positive and 1200 were True Negative. Since Positive Predictive Value is TP/(TP+FP) the sensitivity = 0.444 or 44%. |
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If the same test were performed on an apparently healthy population with a HCC prevalence of 1.0% which of the
following values would you expect to change. A. Specificity B. Sensitivity C. Positive predictive value D. There would be no change in expected specificity, sensitivity and positive predictive values. E. The specificity, sensitivity, and positive predicative value would all change. |
Answer C): Prevalence affects the positive and negative predictive value but not the sensitivity or specificity of an
assay. This can be proven by repeating the calculations in question 7-9 using the new prevalence. |
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Of the series of numbers on the website under question #1, calculate the mode, median, and mean,
respectively. A. 3,3,4.33 B. 4,5,4.33 C. 3,4,4.33 D. 5,4,4.33 E. 4,4,4.33 |
C. 3,4,4.33
C. Mode = most frequent number in a series (3), Median = the midpoint of a series (4), and Mean = average of a series (39/9 = 4.33. Test taking strategy. On questions where they may be asking you to calculate, look at the answers first. Notice in this case you don’t even have to average the numbers. Really this question is only asking to differentiate mode and median of a series. |
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A series of data for a new clinical lab test has a Gaussian distribution. What percent of the data will
be more than 3 standard deviations above the mean? A. 4.5% B. 2.25% C. 0.3% D. 0.15% E. None of the above |
D. 0.15%
D. 3 standard deviations of data in a Gaussian distribution encompasses 99.7% of the test data. The remaining 0.3% is distributed at the two ends of the distribution, and only half (0.15%) will be above the mean. Test taking strategy. Remember that 1 standard deviation contains 68% of the data; 2 standard deviations 95.5% of the data; and 3 standard deviations 99.7% of the data. |
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A new instrument is installed for CBCs, and a correlation test is performed. The reference method is
plotted on the X-axis and the new method on the Y-axis for multiple samples tested. Linear regression analysis is performed (y=mx + b). Which of the following represents the correlation coefficient, r. A. Y-intercept (b) B. Line slope (m) C. Calculation of how well the points fit the line D. None of the above |
C. Calculation of how well the points fit the line
C. The correlation coefficient represents how well data points fit a line. The Y-intercept represents constant bias, and the slope of the line represents proportional bias (e.g. the test always runs 5% higher than the previous test). |
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Which of the following correlation coefficients (r) represents the minimal number you would like to
see when validating a new test? A. 0.3 B. 0.9 C. 0.97 D. 0.99 E. None of the above |
C. 0.97
C. While an r-value of >0.99 is usually achieved when setting up a new test, 0.97 is the lower limit of an acceptable coefficient. An r-value of greater than 0.3 indicates the two methods are affected by the same variables, but this would be horrible for two tests that are supposed to be the same. |
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Of the following answers, which is the best tool to detect bias between two different methods?
A. Gaussian distributions B. T-test C. F-test D. Linear regression analysis E. Bland-Altman plot |
E. Bland-Altman plot
E. The Bland-Altman plot is the most reliable. The difference between the new and old method results are plotted on the y-axis (usually as a percentage), and the reference result on the x-axis. Test taking strategy. The linear regression analysis can also show bias between two methods. The key to answer is realizing the author is testing whether the test taker recognizes what a Bland-Altman plot is (a.k.a. difference or bias plot). The F-test assesses the reproducibility of a new method, which has a Gaussian distribution of data. |
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For a test with a Gaussian distribution, what is the minimum number of representative samples
needed to determine a reference range? A. 20 B. 120 C. 180 D. 200 E. As many as possible |
B. 120
B. 20 is the minimum number of “healthy person” samples needed to validate a previously established reference range (if no more than 2 values fall outside the reference limits). 120 is the minimum number of representative samples needed to create a reference range (if it represents a Gaussian distribution). 200 is the minimum number of representative samples needed to create a reference range, which does not have a Gaussian distribution. |
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For a test without a Gaussian distribution, what is the minimal number of representative samples
needed to establish a reference range? A. 20 B. 120 C. 180 D. 200 E. As many as possible |
D. 200
D. 20 is the minimum number of “healthy person” samples needed to validate a previously established reference range (if no more than 2 values fall outside the reference limits). 120 is the minimum number of representative samples needed to create a reference range (if it represents a Gaussian distribution). 200 is the minimum number of representative samples needed to create a reference range, which does not have a Gaussian distribution. |
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To validate a previously established reference range, what is the minimal number of healthy person
samples needed? A. 20 B. 120 C. 180 D. 200 E. As many as possible |
A. 20
Answer: A. 20 is the minimum number of “healthy person” samples needed to validate a previously established reference range (if no more than 2 values fall outside the reference limits). 120 is the minimum number of representative samples needed to create a reference range (if it represents a Gaussian distribution). 200 is the minimum number of representative samples needed to create a reference range, which does not have a Gaussian distribution. |
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If 20 tests were performed on a “healthy” individual, what is the likelihood all of the results will be
within the reference range? A. 95% B. 60% C. 46% D. 36% E. None of the above |
D. 36%
D. This question points to the fact that reference ranges by convention exclude 5% of the results (95% confidence interval), which is also approximately 2 standard deviations (95.5%). Considering this, the likelihood of n tests falling within the reference range is = 0.95n. Test taking strategy. This is an easy question if you know the equation and have a scientific calculator. Most will not have either. Let’s think of this question more simply. If you consider that reference ranges represent the 95% confidence interval of a distribution, then it will be likely that 1 in 20 tests (i.e. 5%) will be “abnormal” in a “healthy” person. Answers A through C are either close to or greater than 50%; leaving answer D (36%) as the most likely answer. It is recommended that “none of the above” not be used unless all of the other answers can be confidently excluded, or the correct answer is known and not given. |
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The coefficient of variation best represents which of the following:
A. Accuracy B. Precision C. Bias D. Efficiency E. None of the above |
B. Precision
Answer: B. The coefficient of variation = standard deviation divided by the mean (x 100) to be expressed as a percentage. The smaller the standard deviation means the more precise the test. Accuracy is usually expressed as bias, which can be an absolute of percentage (think correlation plots). Efficiency is term used in relative operating characteristic curves. |