CLT Laboratory Equipment Operation & Maintenance 2 — Questions and Answers
Question 1: When performing a Coulter principle cell counter QC check, which parameter most directly reflects RBC volume distribution?
- MCV
- RDW (Correct answer)
- MPV
- PDW
Correct answer: RDW
RDW (Red Cell Distribution Width) directly measures the variability in RBC volume, making it the key parameter for assessing RBC volume distribution on Coulter principle analyzers.
Question 2: A centrifuge rotor shows visible pitting after routine cleaning. The technologist should:
- Continue using it with reduced RPM
- Apply epoxy coating to smooth the surface
- Remove it from service and notify the supervisor immediately (Correct answer)
- Soak it in lubricating oil before next use
Correct answer: Remove it from service and notify the supervisor immediately
Pitting in a centrifuge rotor indicates metal fatigue and potential for catastrophic failure; the rotor must be removed from service immediately as a safety measure.
Question 3: Which component of a spectrophotometer is responsible for isolating a specific wavelength of light?
- Photodetector
- Cuvette holder
- Monochromator (Correct answer)
- Beam splitter
Correct answer: Monochromator
The monochromator (using a prism, diffraction grating, or filter) isolates the desired wavelength of light from a broad-spectrum source for accurate absorbance measurement.
Question 4: A biosafety cabinet (BSC) Class II Type A2 is PRIMARILY designed to protect:
- The product only
- The environment only
- Personnel only
- Personnel, product, and environment (Correct answer)
Correct answer: Personnel, product, and environment
Class II Type A2 BSCs provide triple protection — personnel (via inward airflow), product (via HEPA-filtered downflow), and environment (via HEPA-filtered exhaust).
Question 5: During autoclave validation, biological indicators (BIs) containing Geobacillus stearothermophilus spores are used because these spores:
- Are inexpensive and widely available
- Represent the most heat-resistant organisms (Correct answer)
- Change color rapidly when killed
- Are non-pathogenic and easy to handle
Correct answer: Represent the most heat-resistant organisms
G. stearothermophilus spores are the gold standard BI for steam sterilization because they are among the most heat-resistant organisms, ensuring sterilization efficacy when they are killed.
Question 6: A laboratory thermometer used to monitor a -80°C freezer reads -75°C during a routine check. The FIRST corrective action is to:
- Transfer all samples to liquid nitrogen storage
- Verify the reading with a calibrated NIST-traceable thermometer (Correct answer)
- Immediately service the freezer compressor
- Document the discrepancy and continue monitoring
Correct answer: Verify the reading with a calibrated NIST-traceable thermometer
Before taking action on a temperature discrepancy, the reading must be verified with a calibrated reference thermometer to determine if the issue is with the monitoring thermometer or the freezer itself.
Question 7: When using an automated coagulation analyzer, a prolonged clot detection time on all channels simultaneously most likely indicates:
- Pre-analytical error in sample collection
- Reagent degradation specific to one test
- Instrument optical or mechanical system failure (Correct answer)
- Patient-related hypercoagulable state
Correct answer: Instrument optical or mechanical system failure
When all channels are affected simultaneously, a systemic instrument problem — such as optical sensor failure or mechanical timing error — is the most probable cause rather than individual reagent or sample issues.
CLT Laboratory Equipment Operation & Maintenance 2
When performing a Coulter principle cell counter QC check, which parameter most directly reflects RBC volume distribution?