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The CC exam has 170 questions and runs 6 hours 30 minutes.
These 10 free CC questions are organized by exam domain, so you can see how each part of the Board Certification in Clinical Chemistry blueprint is tested. Reveal the answer and explanation under each question.
A laboratory wishes to run an FDA-cleared serum assay on a body fluid matrix that is not listed in the manufacturer's instructions for use. Under CLIA, what is the regulatory consequence of this change?
Correct answer: C - The assay becomes high complexity and all performance specifications must be established
An assay has a total allowable error of 10%, an observed bias of 2%, and a within-laboratory coefficient of variation of 2%. What is the sigma metric, and what does it imply for quality control design?
Correct answer: A - 4.0 - multirule control with additional control measurements is needed
In a single analytical run, the level 1 control is +2.6 SD from its assigned mean and the level 2 control is -2.4 SD from its assigned mean. Which interpretation is correct?
Correct answer: D - The R-4s rule is violated, indicating random error; reject the run
A serum chemistry panel from an asymptomatic inpatient with a normal ECG shows potassium 9.8 mmol/L, calcium 1.2 mg/dL (0.30 mmol/L), magnesium 0.4 mg/dL, and alkaline phosphatase 8 U/L. All other analytes are unremarkable. What is the MOST likely cause of this pattern?
Correct answer: A - Carryover of EDTA anticoagulant from a lavender-top tube
A 34-year-old woman has TSH less than 0.01 mIU/L (RI 0.4-4.0) and free T4 42 pmol/L (RI 10-22) on a streptavidin-biotin based immunoassay platform. She is clinically euthyroid with a normal thyroid examination and takes a high-dose over-the-counter hair and nail supplement. Testing of the same specimen on a different manufacturer's platform gives normal results. What is the MOST likely explanation?
Correct answer: B - Biotin interference in the streptavidin-biotin capture system
A serum sodium is 124 mmol/L on the main chemistry analyzer, which uses an indirect ion-selective electrode. The identical specimen measured on the blood gas analyzer, which uses a direct ion-selective electrode, gives 139 mmol/L. Total protein is 11.4 g/dL. What is the correct interpretation?
Correct answer: D - The indirect result reflects pseudohyponatremia caused by the increased solid phase
A patient has the following results: pH 7.29, pCO2 29 mm Hg, HCO3- 14 mmol/L, Na+ 139 mmol/L, Cl- 99 mmol/L, K+ 4.2 mmol/L. (Anion gap reference interval 8-12 mmol/L.) Which classification of the acid-base disturbance is correct?
Correct answer: D - High anion gap metabolic acidosis with appropriate respiratory compensation
During a documented episode of hypoglycemia (plasma glucose 38 mg/dL, 2.1 mmol/L), a patient has insulin 45 microIU/mL, C-peptide 0.2 ng/mL, and an appropriately suppressed beta-hydroxybutyrate. A sulfonylurea and meglitinide screen is negative. (Endogenous hyperinsulinism during hypoglycemia is defined by insulin above 3 microIU/mL WITH C-peptide above 0.6 ng/mL.) What is the MOST likely cause?
Correct answer: D - Surreptitious administration of exogenous insulin
A patient presents 2 hours after a suspected ingestion with an osmolal gap of 38 mOsm/kg and an anion gap of 11 mmol/L. Ten hours later, the osmolal gap is 6 mOsm/kg and the anion gap is 29 mmol/L. Which explanation BEST accounts for these serial findings?
Correct answer: B - The parent alcohol has been metabolized to organic acid metabolites
A 29-year-old man has persistent mild hypercalcemia (11.1 mg/dL, 2.78 mmol/L) with an inappropriately normal PTH. The 24-hour urine calcium is low and the calcium-to-creatinine clearance ratio is 0.005. Two siblings have similar biochemistry. What is the MOST likely diagnosis?
Correct answer: A - Familial hypocalciuric hypercalcemia from a CASR variant
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