ASCP Clinical Chemistry 2 — Questions and Answers
Question 1: Which method is the reference standard for measuring serum creatinine?
- Jaffe colorimetric method
- Enzymatic method with isotope dilution mass spectrometry (IDMS) (Correct answer)
- Bradford protein assay
- Biuret method
Correct answer: Enzymatic method with isotope dilution mass spectrometry (IDMS)
IDMS-traceable enzymatic creatinine methods are the current reference standards, eliminating pseudochromogen interference seen with Jaffe.
Question 2: A patient has pH 7.28, PCO2 55 mmHg, and HCO3 24 mEq/L. This is consistent with:
- Metabolic acidosis
- Respiratory acidosis (Correct answer)
- Metabolic alkalosis
- Respiratory alkalosis
Correct answer: Respiratory acidosis
Elevated PCO2 with low pH and normal bicarbonate indicates primary respiratory acidosis from CO2 retention.
Question 3: Which analyte is measured by the Berthelot reaction in clinical chemistry?
- Glucose
- Creatinine
- Ammonia/urea nitrogen (BUN) (Correct answer)
- Bilirubin
Correct answer: Ammonia/urea nitrogen (BUN)
The Berthelot reaction converts ammonia (from urease-hydrolyzed urea) to a colored indophenol compound for BUN measurement.
Question 4: Which fraction of bilirubin is elevated in hepatocellular disease and obstructive jaundice?
- Unconjugated (indirect) only
- Conjugated (direct) only
- Both conjugated and unconjugated (Correct answer)
- Delta bilirubin only
Correct answer: Both conjugated and unconjugated
Hepatocellular and obstructive jaundice both elevate conjugated bilirubin, and impaired uptake also elevates unconjugated bilirubin.
Question 5: The Friedewald equation calculates LDL cholesterol using which formula?
- LDL = Total cholesterol − HDL
- LDL = Total cholesterol − HDL − (TG/5) (Correct answer)
- LDL = HDL + VLDL
- LDL = Total cholesterol × 0.7
Correct answer: LDL = Total cholesterol − HDL − (TG/5)
The Friedewald equation estimates LDL as: Total cholesterol − HDL − (triglycerides/5), valid only when TG < 400 mg/dL.
Question 6: Which electrolyte imbalance is most associated with peaked T-waves on ECG?
- Hyponatremia
- Hypocalcemia
- Hyperkalemia (Correct answer)
- Hypomagnesemia
Correct answer: Hyperkalemia
Hyperkalemia causes tall, peaked T-waves and can progress to fatal arrhythmias if untreated.
ASCP Clinical Chemistry 2
Which method is the reference standard for measuring serum creatinine?