CLT Clinical Chemistry & Biochemical Analysis 2 — Questions and Answers
Question 1: Which of the following best describes the Beer-Lambert Law as applied to spectrophotometry in clinical chemistry?
- Absorbance is inversely proportional to concentration
- Absorbance is directly proportional to concentration and path length (Correct answer)
- Transmittance is directly proportional to concentration
- Absorbance is independent of wavelength
Correct answer: Absorbance is directly proportional to concentration and path length
Beer-Lambert Law states that absorbance equals the product of molar absorptivity, path length, and concentration, meaning absorbance increases linearly with concentration.
Question 2: Hemoglobin A1c (HbA1c) reflects average blood glucose control over approximately what time period?
- 2–4 weeks
- 4–6 weeks
- 8–12 weeks (Correct answer)
- 6–12 months
Correct answer: 8–12 weeks
HbA1c reflects the average plasma glucose over the preceding 8–12 weeks (approximately 3 months), corresponding to the lifespan of red blood cells.
Question 3: Troponin I or T elevation in a patient with chest pain is most indicative of which condition?
- Pulmonary embolism
- Acute pancreatitis
- Acute myocardial infarction (Correct answer)
- Renal failure
Correct answer: Acute myocardial infarction
Cardiac troponins I and T are released from injured myocardial cells and are the gold-standard biomarkers for acute myocardial infarction.
Question 4: Which method is considered the reference (gold standard) for measuring serum cholesterol?
- Enzymatic colorimetric method
- Abell-Kendall method (Correct answer)
- Liebermann-Burchard reaction
- Ion-selective electrode method
Correct answer: Abell-Kendall method
The Abell-Kendall method (saponification followed by Liebermann-Burchard colorimetry under controlled conditions) is the CDC reference method for total cholesterol.
Question 5: An arterial blood gas result shows pH 7.28, pCO2 55 mmHg, and HCO3 26 mEq/L. What is the primary acid-base disturbance?
- Metabolic acidosis
- Metabolic alkalosis
- Respiratory acidosis (Correct answer)
- Respiratory alkalosis
Correct answer: Respiratory acidosis
Elevated pCO2 (>45 mmHg) with a low pH indicates respiratory acidosis caused by CO2 retention.
Question 6: What is the primary purpose of running a calibration curve in clinical chemistry assays?
- To detect instrument malfunctions
- To ensure reagent stability
- To establish the relationship between signal and analyte concentration (Correct answer)
- To verify specimen integrity
Correct answer: To establish the relationship between signal and analyte concentration
A calibration curve plots known standard concentrations against instrument response (absorbance/signal) so that unknown sample concentrations can be calculated by interpolation.
Question 7: Elevated serum amylase and lipase are most characteristic of which condition?
- Hepatitis
- Acute pancreatitis (Correct answer)
- Myocardial infarction
- Renal insufficiency
Correct answer: Acute pancreatitis
Both amylase and lipase are pancreatic enzymes that are released into the bloodstream during acute pancreatitis, making their elevation diagnostic of this condition.
CLT Clinical Chemistry & Biochemical Analysis 2
Which of the following best describes the Beer-Lambert Law as applied to spectrophotometry in clinical chemistry?