CMLA Equipment Maintenance 4 — Questions and Answers
Question 1: During a routine check, a laboratory thermometer reads 2°C higher than the NIST-traceable reference thermometer. What is the correct response?
- Apply a correction factor and document it, or replace the thermometer (Correct answer)
- Continue using the thermometer since 2°C is within typical room variation
- Recalibrate the reference thermometer instead
- Use the thermometer only for non-critical applications
Correct answer: Apply a correction factor and document it, or replace the thermometer
A documented correction factor or thermometer replacement ensures temperature-sensitive specimens and reagents are stored at the true required temperature.
Question 2: What is the function of a rotor imbalance detector in a centrifuge?
- To shut down the centrifuge automatically if unequal loading causes dangerous vibration (Correct answer)
- To measure the RPM of the rotor during operation
- To alert the user when the rotor needs lubrication
- To count the total number of spins logged on the rotor
Correct answer: To shut down the centrifuge automatically if unequal loading causes dangerous vibration
Rotor imbalance detectors prevent mechanical damage and rotor failure by stopping the centrifuge when dangerous vibration is detected.
Question 3: Which laboratory instrument requires a daily linearity check using a neutral density filter set?
- Spectrophotometer (Correct answer)
- Centrifuge
- Autoclave
- Analytical balance
Correct answer: Spectrophotometer
Neutral density filters with certified percent transmittance values are used to verify spectrophotometer photometric linearity.
Question 4: A pipette calibration check shows it consistently delivers 2% less volume than the set value. This type of error is called:
- Systematic (bias) error (Correct answer)
- Random error
- Gross error
- Proportional error only at low volumes
Correct answer: Systematic (bias) error
A consistent directional offset across all measurements is a systematic or bias error, often correctable through recalibration.
Question 5: What should a medical laboratory assistant do before performing any internal maintenance on an automated analyzer?
- Power off the instrument and follow lockout/tagout (LOTO) procedures (Correct answer)
- Wear only gloves and proceed while the instrument is running
- Notify administration and wait 24 hours before servicing
- Run a final QC cycle to document the pre-maintenance state only
Correct answer: Power off the instrument and follow lockout/tagout (LOTO) procedures
LOTO procedures isolate the instrument from its energy source, preventing accidental activation and protecting the technician during internal maintenance.
Question 6: Which component of a biosafety cabinet (BSC) should be tested annually by a certified professional?
- HEPA filter integrity and airflow velocity (Correct answer)
- Fluorescent bulb brightness
- UV lamp wavelength output only
- Electrical outlet functionality inside the cabinet
Correct answer: HEPA filter integrity and airflow velocity
Annual NSF-certified testing of HEPA filter integrity and airflow velocity ensures the BSC provides adequate containment and personnel protection.
Question 7: An automated cell counter gives inconsistent WBC counts on replicate runs of the same sample. After ruling out sample mixing issues, what is the most likely instrument cause?
- A partially blocked aperture or flow cell (Correct answer)
- An expired reagent pack
- An incorrect sample dilution ratio entered by the operator
- A failed internal temperature sensor
Correct answer: A partially blocked aperture or flow cell
A partial clog in the aperture or flow cell causes variable cell counts by disrupting the consistent flow of cells past the detector.
CMLA Equipment Maintenance 4
During a routine check, a laboratory thermometer reads 2°C higher than the NIST-traceable reference thermometer.
What is the correct response?