Clinical Chemistry- Clinical Chemistry Problem Solving

Question 1

1. Which of the following procedures can be used to
   detect proportional error in a new method for
   glucose?
   A. Compare the standard deviation of 40 patient
   samples to the hexokinase method
   B. Measure a mixture made from equal parts of
   normal and high-QC sera
   C. Add 5.0 mg of glucose to 1.0 mL of a serum of
   known concentration and measure
   D. Compare the mean of 40 normal samples to the
   hexokinase method

Answer 1

C. Add 5.0 mg of glucose to 1.0 mL of a serum of
known concentration and measure

Question 2

2. Which of two instruments can be assumed to have
   the narrower bandpass? Assume that wavelength is
   accurately calibrated.
   A. The instrument giving the highest absorbance for
   a solution of 0.1 mmol/L NADH at 340 nm
   B. The instrument giving the lowest %T for a
   solution of nickel sulfate at 700 nm
   C. The instrument giving the highest %T reading
   for 1.0% v/v HCl at 350 nm
   D. The instrument giving the most linear plot of
   absorbance versus concentration

Answer 2

A. The instrument giving the highest absorbance for
a solution of 0.1 mmol/L NADH at 340 nm

Question 3

3. A lipemic sample gives a sodium of 130 mmol/L
   on an analyzer that uses a 1:50 dilution of serum
   or plasma before introducing it to the ion selective
   electrodes. The same sample gives a sodium of
   142 mmol/L using a direct (undiluted) ion
   selective electrode. Assuming acceptable quality
   control, which of the following is the most
   appropriate course of action?
   A. Report a sodium result of 136 mmol/L
   B. Ultracentrifuge the sample and repeat by ISE
   C. Dilute the sample 1:4 and repeat by ISE
   D. Report the undiluted ion selective electrode
   result

Answer 3

D. Report the undiluted ion selective electrode
result

Question 4

4. SITUATION: A 22S QC error occurs for serum
   calcium by atomic absorption. Fresh standards
   prepared in 5.0% w/v albumin are found to be
   linear, but repeating the controls with fresh
   material does not improve the QC results. Select
   the most likely cause of this problem.
   A. Matrix effect caused by a viscosity difference
   between the standards and QC sera
   B. Chemical interference caused incomplete
   atomization
   C. Incomplete deconjugation of protein-bound
   calcium
   D. Ionization interference caused by excessive heat

Answer 4

B. Chemical interference caused incomplete
atomization

Question 5

5. SITUATION: A serum osmolality measured in
   the emergency department is 326 mOsm/kg.

Two hours later, chemistry results are:
Na = 135 mmol/L
BUN = 18 mg/dL
glucose = 72 mg/dL measured osmolality = 318
mOsm/kg

What do these results suggest?
A. Laboratory error in electrolyte or glucose
measurement
B. Drug or alcohol intoxication
C. Specimen misidentification
D. Successful rehydration of the patient

Answer 5

B. Drug or alcohol intoxication

Question 6

6. When calibrating a pH meter, unstable readings
   occur for both pH 7.00 and 4.00 calibrators,
   although both can be set to within 0.1 pH unit.
   Select the most appropriate course of action.
   A. Measure the pH of the sample and report to the
   nearest 0.1 pH
   B. Replace both calibrators with unopened buffers
   and recalibrate
   C. Examine the reference electrode junction for salt
   crystals
   D. Move the electrodes to another pH meter and
   calibrate

Answer 6

C. Examine the reference electrode junction for salt
crystals

Question 7

7. A method calls for extracting an acidic drug from
   urine with an anion exchange column. The pKa
   of the drug is 6.5. Extraction is enhanced by
   adjusting the sample pH to:
   A. 8.5
   B. 6.5
   C. 5.5
   D. 4.5

Answer 7

A. 8.5

Question 8

8. SITUATION: A patient who has a positive
   urinalysis for glucose and ketones has a glycated
   Hgb of 4.0%. A fasting glucose performed the
   previous day was 180 mg/dL. Assuming acceptable
   QC, you would:
   A. Report the glycosylated Hgb
   B. Request a new specimen and repeat the
   glycosylated Hgb
   C. Perform a Hgb electrophoresis on the sample
   D. Perform a glucose measurement on the sample

Answer 8

B. Request a new specimen and repeat the
glycosylated Hgb

Question 9

9. Quality control results for uric acid are as follows:

Results should be reported from:
A. Run 1 only
B. Runs 1 and 2
C. Runs 1, 2, and 3
D. Runs 1, 2, 3, and 4

Answer 9

C. Runs 1, 2, and 3

Question 10

10. SITUATION: A peak blood level for orally
    administered theophylline (therapeutic
    range 8–20 mg/L) measured at 8 a.m. is
    5.0 mg/L. The preceding trough level was
    4.6 mg/L. What is the most likely explanation
    of these results?
    A. Laboratory error made on peak measurement
    B. Specimen for peak level was collected from
    wrong patient
    C. Blood for peak level was drawn too soon
    D. Elimination rate has reached maximum

Answer 10

C. Blood for peak level was drawn too soon

Question 11

11. SITUATION: A patient breathing room air has the
    following arterial blood gas and electrolyte results:

pH = 7.54
PCO2 = 18.5 mm Hg
PO2 = 145 mm Hg
HCO3 = 18 mmol/L
Na = 135 mmol/L
K = 4.6 mmol/L

Cl = 98 mmol/L
TCO2 = 20 mmol/L

The best explanation for these results is:

A. Blood for electrolytes was drawn above an IV
B. Serum sample was hemolyzed
C. Venous blood was sampled for arterial blood
gases
D. Blood gas sample was exposed to air

Answer 11

D. Blood gas sample was exposed to air

Question 12

12. SITUATION: The following lab results are
    reported. Which result is most likely to be
    erroneous?

Arterial blood gases:
pH = 7.42
pO2 = 90 mm Hg
pCO2 = 38.0 mm Hg bicarbonate = 24 mmol/L.

Plasma electrolytes:
Na = 135 mmol/L
Cl = 98 mmol/L
K = 4.6 mmol/L
TCO2 = 33 mmol/L

A. pH
B. Na
C. K
D. TCO2

Answer 12

D. TCO2

Question 13

13. SITUATION: Laboratory results on a patient from
    the emergency department are:

glucose =1,100 mg/dL
Na = 155 mmol/L
K = 1.2 mmol/L

Cl = 115 mmol/L
TCO2 = 3.0 mmol/L

What is the most likely explanation of these
results?

A. Sample drawn above an IV
B. Metabolic acidosis with increased anion gap
C. Diabetic ketoacidosis
D. Laboratory error measuring electrolytes caused
by hyperglycemia

Answer 13

A. Sample drawn above an IV

Question 14

14. SITUATION: A plasma sample from a person in a
    coma as a result of an automobile accident gave the following results:

Total CK 480 IU/L CK-MB 8 μg/L
Myoglobin 800 μg/L Troponin I 0.02 μg/L

What is the best interpretation of these results?

A. The person had a heart attack that caused the
accident
B. The accident caused traumatic injury, but no
heart attack occurred
C. A heart attack occurred in addition to a stroke
D. It is not possible to tell whether a heart attack
occurred because of the extensive trauma

Answer 14

B. The accident caused traumatic injury, but no
heart attack occurred

Question 15

15. SITUATION: A patient has the following
    electrolyte results:

Na = 130 mmol/L
K = 4.8 mmol/L
Cl = 105 mmol/L
TCO2 = 26 mmol/L

Assuming acceptable QC, select the best course
of action.

A. Report these results
B. Check the albumin, total protein, Ca, P, and
Mg results; if normal, repeat the sodium test
C. Request a new sample
D. Recalibrate and repeat the potassium test

Answer 15

B. Check the albumin, total protein, Ca, P, and
Mg results; if normal, repeat the sodium test

Question 16

16. A stat plasma lithium determined using an
    ion-selective electrode is measured at
    14.0 mmol/L. Select the most appropriate
    course of action.
    A. Immediately report this result
    B. Check sample for hemolysis
    C. Call for a new specimen
    D. Rerun the lithium calibrators

Answer 16

C. Call for a new specimen

Question 17

17. A chromatogram for blood alcohol (GC) gives
    broad trailing peaks and increased retention times
    for ethanol and internal standard. This is most
    likely caused by:

A. A contaminated injection syringe
B. Water contamination of the column packing
C. Carrier gas flow rate that is too fast
D. Oven temperature that is too high

Answer 17

B. Water contamination of the column packing

Question 18

18. SITUATION: An amylase result is 550 U/L.
    A 1:4 dilution of the specimen in NaCl gives
    180 U/L (before mathematical correction for
    dilution). The dilution is repeated with the same
    results. The technologist should:

A. Report the amylase as 550 U/L
B. Report the amylase as 720 U/L
C. Report the amylase as 900 U/L
D. Dilute the sample 1:10 in distilled water
and repeat

Answer 18

B. Report the amylase as 720 U/L

Question 19

19. SITUATION: A patient’s biochemistry results are:

ALT = 55 IU/L
AST = 165 IU/L
glucose = 87 mg/dL
LD = 340 IU/L
Na = 142 mmol/L
K = 6.8 mmol/L
Ca = 8.4 mg/dL
Pi = 7.2 mg/dL
Select the best course of action.

A. Report results along with an estimate of the
degree of hemolysis
B. Repeat LD but report all other results
C. Request a new sample
D. Dilute the serum 1:2 and repeat AST and LD

Answer 19

A. Report results along with an estimate of the
degree of hemolysis

Question 20

20. A blood sample is left on a phlebotomy tray for
    4.5 hours before it is delivered to the laboratory.
    Which group of tests could be performed?
    A. Glucose, Na, K, Cl, TCO2
    B. Uric acid, BUN, creatinine
    C. Total and direct bilirubin
    D. CK, ALT, ALP, AST

Answer 20

B. Uric acid, BUN, creatinine

Question 21

21. An HPLC assay for procainamide gives an
    internal standard peak that is 15% greater in area
    and height for sample 1 than sample 2. The
    technologist should suspect that:
    A. The column pressure increased while sample 2
    was being analyzed
    B. Less recovery from sample 2 occurred in the
    extraction step
    C. The pH of the mobile phase increased during
    chromatography of sample 2
    D. There was more procainamide in sample 1 than
    sample 2

Answer 21

B. Less recovery from sample 2 occurred in the
extraction step

Question 22

22. After staining a silica gel plate to determine the
    L/S ratio, the technologist notes that the lipid
    standards both migrated 1 cm faster than usual.
    The technologist should:
    A. Repeat the separation on a new silica gel plate
    B. Check the pH of the developing solvent
    C. Prepare fresh developing solvent and repeat
    the assay
    D. Reduce solvent migration time for all
    subsequent runs

Answer 22

C. Prepare fresh developing solvent and repeat
the assay

Question 23

23. A quantitative urine glucose was determined to
    be 160 mg/dL by the Trinder glucose oxidase
    method. The sample was refrigerated overnight.
    The next day, the glucose is repeated and found to
    be 240 mg/dL using a polarographic method.
    What is the most likely cause of this discrepancy?
    A. Poor precision when performing one of the
    methods
    B. Contamination resulting from overnight storage
    C. High levels of reducing substances interfering
    with the Trinder reaction
    D. Positive interference in the polarographic
    method caused by hematuria

Answer 23

C. High levels of reducing substances interfering
with the Trinder reaction

Question 24

24. SITUATION: Results of an iron profile are:
    serum Fe = 40 μg/dL
    TIBC = 400 μg/dL
    ferritin = 40μg/L
    transferrin = 300 mg/dL
    (reference range 15–200)

These results indicate:
A. Error in calculation of TIBC
B. Serum iron falls before ferritin in iron deficiency
C. A defect in iron transport and not Fe deficiency
D. Excess release of ferritin caused by injury

Answer 24

D. Excess release of ferritin caused by injury

Question 25

25. SITUATION: Results of an iron profile are:
    Serum Fe =40 μg/dL
    TIBC =400 μg/dL
    ferritin = 50 μg/L

All of the following tests are useful in establishing
a diagnosis of Fe deficiency except:
A. Protein electrophoresis
B. Erythrocyte zinc protoporphyrin
C. Serum transferrin
D. Hgb electrophoresis

Answer 25

D. Hgb electrophoresis

Question 26

26. Serum protein and immunofixation electrophoresis
    are ordered on a patient. The former is performed,
    but there is no evidence of a monoclonal protein.
    Select the best course of action.
    A. Perform quantitative Ig G, A, M
    B. Perform the IFE on the serum
    C. Report the result; request a urine sample for
    protein electrophoresis
    D. Perform IFE on the serum and request a urine
    sample for IFE

Answer 26

C. Report the result; request a urine sample for
protein electrophoresis

Question 27

27. SITUATION: Hgb electrophoresis is performed
    and all of the Hgbs have greater anodal mobility
    than usual. A fast Hgb (Hgb H) is at the edge of
    the gel and bands are blurred. The voltage is set
    correctly, but the current reading on the ammeter
    is too low. Select the course of action that would
    correct this problem.
    A. Reduce the voltage
    B. Dilute the buffer and adjust the pH
    C. Prepare fresh buffer and repeat the test
    D. Reduce the running time

Answer 27

C. Prepare fresh buffer and repeat the test

Question 28

28. A technologist is asked to use the serum from a
    clot tube left over from a chemistry profile run at
    8 a.m. for a stat ionized calcium (Cai
    ) at 11 a.m.
    The technologist should:
    A. Perform the assay on the 8 a.m. sample
    B. Perform the test only if the serum container was
    tightly capped
    C. Perform the assay on the 8 a.m. sample only if it
    was refrigerated
    D. Request a new sample

Answer 28

D. Request a new sample

Question 29

29. SITUATION: A patient’s biochemistry results are:
    Na = 125 mmol/L
    Cl = 106 mmol/L
    K = 4.5 mmol/L
    TCO2 = 19 mmol/L
    chol = 240 mg/dL
    triglyceride = 640 mg/dL glucose = 107 mg/dL
    AST = 16 IU/L
    ALT = 11 IU/L
    amylase = 200 U/L

Select the most likely cause of these results.
A. The sample is hemolyzed
B. Serum was not separated from cells in
sufficient time
C. Lipemia is causing in vitro interference
D. The specimen is contaminated

Answer 29

C. Lipemia is causing in vitro interference

Question 30

30. A gastric fluid from a patient suspected of having
    taken an overdose of amphetamine is sent to the
    laboratory for analysis. The technologist should:
    A. Perform an EMIT assay for amphetamine
    B. Refuse the sample and request serum or urine
    C. Dilute 1:10 with H2O and filter; perform TLC
    for amphetamines
    D. Titrate to pH 7.0, then follow procedure for
    measuring amphetamine in urine

Answer 30

C. Dilute 1:10 with H2O and filter; perform TLC
for amphetamines

Question 31

31. SITUATION: Results of biochemistry tests are:
    Na = 138 mmol/L
    K = 4.2 mmol/L
    Cl = 94 mmol/L
    TCO2 = 20 mmol/L
    glucose = 100 mg/dL
    T bili = 1.2 mg/dL
    BUN = 6.8 mg/dL
    creat = 1.0 mg/dL
    albumin = 4.8 g/dL
    T protein = 5.1 g/dL

What should be done next?
A. Request a new specimen
B. Repeat the total protein
C. Repeat all tests
D. Perform a protein electrophoresis

Answer 31

B. Repeat the total protein

Question 32

32. The following chart compares the monthly total
    bilirubin mean of Laboratory A to the monthly
    mean of Laboratory B, which uses the same
    control materials, analyzer, and method.

Both laboratories performed controls at the
beginning of each shift using commercially
prepared liquid QC serum stored at –20°C. Which
of the following conditions would explain these
differences?
A. Improper handling of the control material by
Laboratory A resulted in loss of bilirubin due to
photodegradation
B. The laboratories used a different source of
bilirubin calibrator
C. Laboratory B obtained higher results because its
precision was poorer
D. Carryover from another reagent falsely elevated
the results of Laboratory B

Answer 32

B. The laboratories used a different source of
bilirubin calibrator

Question 33

33. After installing a new analyzer and reviewing
    the results of patients for 1 month, the lead
    technologist notices a greater frequency of patients
    with abnormally high triglyceride results. Analysis
    of all chemistry profiles run the next day indicated
    that triglyceride results are abnormal whenever the
    test is run immediately after any sample that is
    measured for lipase. These observations point to
    which type of error?
    A. Specificity of the triglyceride reagents
    B. Precision in pipetting of lipemic samples
    C. Bias caused by sequence of analysis
    D. Reagent carryover

Answer 33

D. Reagent carryover

Question 34

34. SITUATION: A digoxin result from a stable
    patient with a normal electrocardiogram (EKG)
    is reported as 7.4 ng/mL (URL 2.6 ng/mL) using
    an immunofluorescent method. Renal function
    tests were normal and the patient was not taking
    any other medications. The assay was repeated
    and results were the same. The sample was
    frozen and sent to a reference laboratory for
    confirmation. The result was 1.6 ng/mL measured
    by a competitive chemiluminescent procedure.
    Which best explains the discrepancy in results?
    A. The fluorescent immunoassay was performed
    improperly
    B. Digoxin was lower by the chemiluminescent
    method because it is less sensitive
    C. An interfering substance was present that
    cross-reacted with the antibody in the
    fluorescent immunoassay
    D. Freezing the specimen caused lower results by
    converting the digoxin to an inactive metabolite

Answer 34

C. An interfering substance was present that
cross-reacted with the antibody in the
fluorescent immunoassay

Question 35

35. The following results are reported on an adult
    male patient being evaluated for chest pain:

What is the most likely cause of these results?
A. The wrong sample was assayed for the
first myoglobin
B. The patient did not suffer an MI until after
admission
C. Hemolysis caused interference with the 3-hour
and 6-hour myoglobin result
D. The patient is experiencing unstable angina

Answer 35

A. The wrong sample was assayed for the
first myoglobin

Question 36

36. Analysis of normal and abnormal QCs performed
    at the beginning of the evening shift revealed a
    22s error across levels for triglyceride. Both
    controls were within the 3s limit. The controls
    were assayed again, and one control was within
    the acceptable range and the other was slightly
    above the 2s limit. No further action was taken
    and the patient results that were part of the run
    were reported. Which statement best describes
    this situation?
    A. Appropriate operating procedures were followed
    B. Remedial evaluation should have been taken,
    but otherwise, the actions were appropriate
    C. Corrective action should have been taken before
    the controls were repeated
    D. The controls should have been run twice before
    reporting results

Answer 36

C. Corrective action should have been taken before
the controls were repeated

Question 37

37. A biochemical profile routinely performed
    bimonthly on a renal dialysis patient showed a
    decreased serum calcium and decreased PTH level.
    Such a lab result may be explained by which of
    the following circumstances?
    A. Malignancy
    B. Aluminum toxicity
    C. Hypervitaminosis D
    D. Acidosis

Answer 37

B. Aluminum toxicity

Question 38

38. Which set of the following laboratory results is most likely from a patient who has suffered an
    AMI? Reference intervals are in parenthesis

Answer 38

B.

Question 39

39. Hemoglobin electrophoresis performed on agarose
    at pH 8.8 gives the following results:

All components of the Hgb C, S, F, A control
hemolysate were within the acceptable range.
What is the most likely cause of this patient’s
result?
A. HgbLepore
B. Hgb S-β-thalassemia (Hgb S/β+)
C. Hgb SC disease post-transfusion
D. Specimen contamination

Answer 39

C. Hgb SC disease post-transfusion

Question 40

40. Two consecutive serum samples give the results
    shown in the table above (at the top of this page)
    for a metabolic function profile.
    The instrument is a random access analyzer
    that uses two sample probes. The first probe
    aspirates a variable amount of serum for the
    spectrophotometric chemistry tests, and the
    second probe makes a 1:50 dilution of serum
    for electrolyte measurements. What is the most
    likely cause of these results?
    A. Both patients have renal failure
    B. There is an insufficient amount of sample in both
    serum tubes
    C. There is a fibrin strand in the probe used for the
    spectrophotometric chemistry tests
    D. The same patient’s sample was accidentally run
    twice

Answer 40

C. There is a fibrin strand in the probe used for the
spectrophotometric chemistry tests

Question 41

41. SITUATION: A blood sample in a red-stoppered
    tube is delivered to the laboratory for electrolytes,
    calcium, and phosphorus. The tube is
    approximately half full and is accompanied by a
    purple-stoppered tube for a complete blood count
    that is approximately three-quarters full. The
    chemistry results are as follows:

What is the most likely explanation of these serum
calcium results?
A. Severe hemolysis during sample collection
B. Laboratory error in the calcium measurement
C. The wrong order of draw was used for vacuum
tube collection
D. Some anticoagulated blood was added to the
red-stoppered tube

Answer 41

D. Some anticoagulated blood was added to the
red-stoppered tube

Question 42

42. SITUATION: A patient previously diagnosed with
    primary hypothyroidism and started on thyroxine
    replacement therapy is seen for follow-up testing
    after 2 weeks. The serum-free T4 is normal but the
    TSH is still elevated. What is the most likely
    explanation for these results?
    A. Laboratory error in measurement of free T4
    B. Laboratory error in measurement of TSH
    C. In vitro drug interference with the free T4 assay
    D. Results are consistent with a euthyroid patient in
    the early phase of therapy

Answer 42

D. Results are consistent with a euthyroid patient in
the early phase of therapy

Question 43

43. SITUATION: A 6-year-old child being treated
    with phenytoin was recently placed on valproic
    acid for better control of seizures. After displaying
    signs of phenytoin toxicity including ataxia,
    a stat phenytoin is determined to be 15.0 mg/L
    (reference range 10–20 mg/L). A peak blood level
    drawn 5 hours after the last dose is 18.0 mg/L.
    The valproic acid measured at the same time is
    within therapeutic limits. Quality control is within
    acceptable limits for all tests, but the physician
    questions the accuracy of the results. What is the
    most appropriate next course of action?
    A. Repeat the valproic acid level using the last
    specimen
    B. Repeat the phenytoin on both trough and peak
    samples using a different method
    C. Recommend measurement of free phenytoin
    using the last specimen
    D. Recommend a second trough level be measured

Answer 43

C. Recommend measurement of free phenytoin
using the last specimen

Question 44

44. The results shown in the table above are
    obtained from three consecutive serum samples
    using an automated random access analyzer
    that samples directly from a bar-coded tube.
    Calibration and QC performed at the start of
    the shift are within the acceptable range, and no
    error codes are reported by the analyzer for
    any tests on the three samples. Upon results
    verification, what is the most appropriate course
    of action?
    A. Report the results and proceed with other tests
    since no analytical problems are noted
    B. Repeat the controls before continuing with
    further testing, but report the results
    C. Check sample identification prior to reporting
    D. Do not report BUN results for these patients or
    continue BUN testing

Answer 44

D. Do not report BUN results for these patients or
continue BUN testing

Question 45

45. An AFP measured on a 30-year-old pregnant
    woman at approximately 12 weeks gestation is
    2.5 multiples of the median (MOM). What
    course of action is most appropriate?
    A. Repeat the serum AFP in 2 weeks
    B. Recommend AFP assay on amniotic fluid
    C. Repeat the AFP using the same sample by
    another method
    D. Repeat the AFP using the sample by the same
    method

Answer 45

A. Repeat the serum AFP in 2 weeks

Question 46

46. SITUATION: Biochemistry tests are performed
    24 hours apart on a patient and delta-check
    flag is reported for inorganic phosphorus by
    the laboratory information system. Given the
    results shown in the table above, identify the
    most likely cause.
    A. Results suggest altered metabolic status caused by
    poor insulin control
    B. The patient was not fasting when the sample was
    collected on day 2
    C. The samples were drawn from two different
    patients
    D. The delta-check limit is invalid when samples are
    collected 24 or more hours apart

Answer 46

B. The patient was not fasting when the sample was
collected on day 2

Question 47

47. A quantitative sandwich enzyme immunoassay for
    intact serum hCG was performed on week 4 and
    the result was 40,000 mIU/mL (reference range
    10,000–80,000 mIU/mL). The physician
    suspected a molar pregnancy and requested that
    the laboratory repeat the test checking for the
    hook effect. Which process would identify this
    problem?
    A. Obtain a new plasma specimen and heat
    inactivate before testing
    B. Obtain a urine specimen and perform the assay
    C. Perform a qualitative pregnancy test
    D. Perform a serial dilution of the sample and repeat
    the test

Answer 47

D. Perform a serial dilution of the sample and repeat
the test

Question 48

48. A patient presents to the emergency department
    with symptoms of intoxication including impaired
    speech and movement. The plasma osmolality was
    measured and found to be 330 mOs/kg. The
    osmolal gap was 40 mOsm/Kg. A blood alcohol
    was measured by the alcohol dehydrogenase
    method and found to be 0.15% w/v (150 mg/dL).
    Electrolyte results showed an increased anion gap.
    Ethylene glycol intoxication was suspected because
    the osmolal gap was greater than could be explained
    by ethanol alone, but gas chromatography was not
    available. Which of the following would be
    abnormal if this suspicion proved correct?
    A. Arterial blood gases
    B. Lactic acid
    C. Urinary ketones
    D. Glucose

Answer 48

A. Arterial blood gases

Question 49

49. Given the serum protein electrophoresis pattern
    shown, which transaminase results would you
    expect?

A. Within normal limits for both
B. Marked elevation of both (20–50-fold normal)
C. Mild elevations of both (2–5-fold normal)
D. Marked elevation of AST but normal ALT

Answer 49

C. Mild elevations of both (2–5-fold normal)

Question 50

50. Serial TnI assays are ordered on a patient at
    admission, 3 hours, and 6 hours afterwards.
    The samples were collected in heparinized
    plasma separator tubes.

Following are the results
(reference range 0–0.03 μg/L)
Admission =0.03 μg/L
3 hours =0.07 μg/L
6 hours = 0.02 μg/L

These results indicate:
A. A positive test for acute myocardial infarction
B. Unstable angina
C. Cardiac injury of severity less than myocardial
infarction
D. Random error with the 3-hour sample

Answer 50

D. Random error with the 3-hour sample