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ABPath Chemical Pathology Subspecialty Certification Examination Practice Test

Chemical pathology interprets biochemical measurements in the context of physiology, disease, and laboratory method. The available practice questions sample electrolyte and acid-base disorders, kidney and adrenal testing, cardiac biomarkers, calcium and enzyme interpretation, and analytical or preanalytical effects that can alter reported results.

Exam overview

Exam providerAmerican Board of Pathology
Exam codeNot listed
CategoryPhysician Board Certification

About the ABPath Chemical Pathology Subspecialty Certification Examination Exam

Useful chemical pathology reasoning links a laboratory pattern to its mechanism and checks whether the measurement is analytically trustworthy. This includes interpreting anion and osmolal gaps in toxic alcohol exposure, recognizing pseudohyponatremia from indirect ion-selective electrode methods, and investigating discordant chemistry and blood-gas results. Questions also exercise selection of alternative filtration markers when creatinine may be affected by assay interference, interpretation of total calcium when albumin is low, and differentiation of alkaline phosphatase sources using related enzyme results. Other scenarios require applying test sensitivity and specificity to low-prevalence screening, choosing cardiac troponin for suspected myocardial injury, assessing adrenal reserve, and using urine chloride to classify metabolic alkalosis. These tasks reflect the laboratory physician’s role in evaluating method limitations, result consistency, and clinical relevance.

Sample Practice Questions

Review a selection from this exam's published US Practice Tests practice bank.

Question 1

A patient with suspected ethylene glycol ingestion has an increased anion gap and calcium oxalate crystals in urine. Which metabolite is most directly responsible for the increased anion gap in this poisoning?

  1. AFormate
  2. BGlycolate
  3. CAcetoacetate
  4. DLactate
Show answerCorrect answer: B

Ethylene glycol is metabolized through several intermediates, including glycolate, which is a major contributor to the high-anion-gap metabolic acidosis. Oxalate formation is associated with calcium oxalate deposition but is not the principal explanation for the gap.

Question 2

A patient with severe hypertriglyceridemia has a sodium concentration of 121 mmol/L by indirect ion-selective electrode, while measured serum osmolality is normal. Which explanation best accounts for this discrepancy?

  1. APseudohyponatremia caused by reduced plasma water fraction affecting the indirect measurement
  2. BTrue hypotonic hyponatremia caused by excess antidiuretic hormone
  3. CHypertonic hyponatremia caused by an unmeasured osmole
  4. DSodium loss from renal tubular dysfunction
Show answerCorrect answer: A

Indirect ion-selective electrodes dilute the specimen and assume a typical plasma water fraction. Marked lipemia reduces that fraction and can yield a falsely low sodium result, whereas direct ion-selective electrodes are not affected in the same way. Normal measured osmolality supports pseudohyponatremia rather than true hypotonic hyponatremia.

Question 3

A laboratory reports a serum total carbon dioxide concentration that is substantially lower than the bicarbonate calculated from a blood gas obtained at nearly the same time. Which preanalytical issue can cause a falsely low total carbon dioxide result in the chemistry specimen?

  1. AProlonged exposure of the specimen to air
  2. BBrief refrigeration before analysis
  3. CCollection in a serum separator tube
  4. DMild lipemia
Show answerCorrect answer: A

Carbon dioxide can escape from an inadequately sealed or exposed specimen, lowering measured total carbon dioxide. Comparison with calculated bicarbonate from a blood gas can reveal a discrepancy, but specimen timing and handling should also be considered.

Question 4

A patient with a markedly elevated alkaline phosphatase concentration has normal gamma-glutamyl transferase activity. Which source is more likely to account for the alkaline phosphatase elevation?

  1. AHepatobiliary epithelium
  2. BBone
  3. CPancreatic acinar cells
  4. DSkeletal muscle
Show answerCorrect answer: B

Alkaline phosphatase can originate from liver or bone, among other tissues. Gamma-glutamyl transferase is commonly increased with hepatobiliary alkaline phosphatase elevation but is not generally increased by bone disease, so this pattern favors a bone source.

Question 5

A patient has a serum creatinine result that is unexpectedly high after receiving a medication known to interfere with some creatinine assays. Which alternative measurement can help assess filtration without relying on creatinine?

  1. ACystatin C
  2. BSerum amylase
  3. CAlkaline phosphatase
  4. DTotal bilirubin
Show answerCorrect answer: A

Cystatin C is a low-molecular-weight protein produced by nucleated cells and filtered by the glomeruli. It can provide an alternative estimate of glomerular filtration when creatinine is affected by nonrenal factors or assay interference, although cystatin C also has non-GFR determinants.

Question 6

A patient with chronic kidney disease has a low serum albumin concentration. When interpreting total calcium, which principle is most appropriate?

  1. ALow albumin can lower total calcium without a corresponding decrease in ionized calcium
  2. BLow albumin necessarily indicates an equivalent decrease in ionized calcium
  3. CTotal calcium is independent of protein binding
  4. DIonized calcium is reliably calculated from total calcium without considering pH
Show answerCorrect answer: A

A substantial portion of circulating calcium is albumin-bound. Hypoalbuminemia may lower measured total calcium while ionized calcium remains within its physiologic range. Direct ionized calcium measurement is useful when protein concentration, pH, or clinical context makes total calcium difficult to interpret.

Question 7

A screening test for a low-prevalence condition has high sensitivity but only moderate specificity. In an asymptomatic population, what is the most likely effect on positive results?

  1. AA substantial proportion may be false positives
  2. BEvery positive result will have a high positive predictive value
  3. CThe negative predictive value must be low
  4. DSpecificity will increase as prevalence decreases
Show answerCorrect answer: A

Positive predictive value depends on prevalence as well as sensitivity and specificity. When prevalence is low, false-positive results among the many unaffected individuals can comprise a substantial fraction of all positive results, even when sensitivity is high.

How to use this practice test

The free US Practice Tests practice bank contains 50 published questions; each session presents up to 20 random questions. Submit a session to see results, then use missed or uncertain items to identify which biochemical mechanisms, assay limitations, or result interpretations need further review.

Preparation tips

  • For acid-base cases, calculate the anion gap and relate it to the responsible metabolite; compare serum total carbon dioxide with blood-gas bicarbonate when specimen handling may have affected the chemistry result.
  • Distinguish true sodium abnormalities from pseudohyponatremia by considering indirect ion-selective electrode measurement and measured serum osmolality.
  • Practice evaluating assay interference and alternative biomarkers, including cystatin C when creatinine may be unreliable and cardiac troponin when assessing myocardial injury.
  • Interpret calcium and alkaline phosphatase alongside relevant context: albumin for total calcium and gamma-glutamyl transferase when assessing a possible hepatobiliary source.
  • Use pretest probability and urine chloride to reason through screening-test results and chloride-responsive metabolic alkalosis.
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