CLC Instrumentation & Technology Applications 2 — Questions and Answers
Question 1: Which detection principle do most modern hematology analyzers use to differentiate cell populations by size?
- Electrical impedance (Coulter principle) (Correct answer)
- Turbidimetry
- Nephelometry
- Bioluminescence
Correct answer: Electrical impedance (Coulter principle)
Modern hematology analyzers primarily use electrical impedance (Coulter principle), measuring the change in electrical resistance as cells pass through an aperture.
Question 2: In mass spectrometry-based clinical assays, what does the term 'internal standard' most directly address?
- Matrix effects and extraction variability (Correct answer)
- Instrument calibration drift over time
- Chromatographic column degradation
- Ionization source contamination
Correct answer: Matrix effects and extraction variability
An internal standard, typically a stable isotope-labeled analog of the analyte, compensates for matrix effects and variability introduced during sample preparation and extraction.
Question 3: A laboratory consultant evaluating a new automated coagulation analyzer notes it uses clot-based detection. Which physical principle underlies this method?
- Change in optical absorbance or turbidity as fibrin forms (Correct answer)
- Fluorescent tagging of clotting factors
- Electrochemical oxidation of thrombin substrates
- Impedance increase from platelet aggregation
Correct answer: Change in optical absorbance or turbidity as fibrin forms
Clot-based coagulation analyzers detect fibrin clot formation by monitoring the increase in optical turbidity or the change in absorbance as the clot develops.
Question 4: Which chromatographic technique is most commonly used in clinical laboratories for therapeutic drug monitoring via LC-MS/MS?
- Reversed-phase high-performance liquid chromatography (RP-HPLC) (Correct answer)
- Ion-exchange chromatography
- Size-exclusion chromatography
- Affinity chromatography
Correct answer: Reversed-phase high-performance liquid chromatography (RP-HPLC)
Reversed-phase HPLC is the predominant separation technique paired with tandem mass spectrometry for therapeutic drug monitoring due to its versatility with small hydrophobic molecules.
Question 5: A laboratory's point-of-care blood gas analyzer produces a result that differs significantly from the central laboratory result on the same sample. Which factor is MOST likely responsible?
- Pre-analytical differences including air bubble exposure and time delay (Correct answer)
- Calibrator lot number discrepancy
- Electrode membrane fouling on the central analyzer
- Different reference ranges between platforms
Correct answer: Pre-analytical differences including air bubble exposure and time delay
Blood gas values are highly sensitive to pre-analytical variables such as air bubble contamination, delay in analysis, and improper sample handling, which commonly explain POC vs. central lab discordance.
Question 6: In flow cytometry, the parameter 'side scatter' (SSC) primarily provides information about which cellular characteristic?
- Internal complexity and granularity (Correct answer)
- Cell size and volume
- Surface antigen density
- Membrane integrity
Correct answer: Internal complexity and granularity
Side scatter (SSC) reflects light scattered at 90° to the laser beam and correlates with internal cellular complexity, such as granularity and nuclear lobularity.
Question 7: When validating a new automated urinalysis system, which parameter is MOST critical to verify using urine reference materials of known composition?
- Linearity and carryover for quantitative analytes such as glucose and protein (Correct answer)
- Reagent strip color intensity under ambient lighting
- Centrifuge speed for microscopic preparation
- Urine collection container compatibility
Correct answer: Linearity and carryover for quantitative analytes such as glucose and protein
Validating linearity and carryover for quantitative analytes ensures the analyzer accurately measures across the reportable range and that high-concentration specimens do not contaminate subsequent samples.
CLC Instrumentation & Technology Applications 2
Which detection principle do most modern hematology analyzers use to differentiate cell populations by size?