CABT Laboratory Equipment 5 — Questions and Answers
Question 1: Which error in a clinical laboratory water purification system would most directly affect enzyme assays performed that day?
- Elevated particulate matter
- Elevated conductivity indicating ion contamination (Correct answer)
- Low UV absorbance reading
- Microbial count above threshold
Correct answer: Elevated conductivity indicating ion contamination
Elevated conductivity signals the presence of ionic contaminants that can inhibit enzyme activity and alter assay results significantly.
Question 2: What is the recommended action when an automated analyzer's QC result exceeds the 3-SD (3 standard deviation) Westgard rule?
- Report patient results with a flag and continue
- Reject the run, investigate the cause, and do not report patient results until resolved (Correct answer)
- Repeat QC once and report if within 2 SD on the second run
- Adjust calibration to bring QC within range
Correct answer: Reject the run, investigate the cause, and do not report patient results until resolved
A 3-SD violation (1₃s rule) indicates random error and requires run rejection, root cause investigation, and re-running QC before releasing patient results.
Question 3: Which component of a flame atomic absorption spectrometer (AAS) produces the specific wavelength of light for the analyte being measured?
- Monochromator
- Hollow cathode lamp (Correct answer)
- Flame burner
- Photomultiplier tube
Correct answer: Hollow cathode lamp
The hollow cathode lamp contains the element of interest and emits its characteristic spectral lines used as the light source in AAS.
Question 4: A biomedical technician is performing a leak test on an automated blood gas analyzer. Which analyte measurement is most sensitive to a small air bubble entering the measuring chamber?
- Sodium (Na+)
- pO₂ (partial pressure of oxygen) (Correct answer)
- pH
- Glucose
Correct answer: pO₂ (partial pressure of oxygen)
pO₂ is most sensitive to air contamination because ambient air has a much higher oxygen tension (~160 mmHg) than blood, causing falsely elevated readings.
Question 5: What is the purpose of a 'dead weight tester' in the context of biomedical equipment maintenance?
- Testing defibrillator output energy
- Calibrating pressure gauges and transducers using known gravitational force on calibrated masses (Correct answer)
- Measuring mechanical force on ventilator valves
- Testing scale accuracy in the laboratory
Correct answer: Calibrating pressure gauges and transducers using known gravitational force on calibrated masses
A dead weight tester applies precise, known pressure using calibrated masses and gravity to calibrate and verify pressure gauges and transducers.
Question 6: When validating a new lot of control material for a chemistry analyzer, which statistical comparison is most important?
- Comparing the new lot expiration date to the old lot
- Performing parallel testing of old and new lots and comparing means and SDs (Correct answer)
- Checking that the new lot is the same color as the old lot
- Confirming the new lot was manufactured by the same company
Correct answer: Performing parallel testing of old and new lots and comparing means and SDs
Parallel testing of old and new control lots allows statistical comparison of means and standard deviations to confirm acceptable lot-to-lot performance before transitioning.
Question 7: A coagulation analyzer displays a 'clot detect error' on a patient sample. The MOST likely cause is:
- Insufficient sample volume or presence of a fibrin clot in the sample (Correct answer)
- Wrong reagent lot number loaded
- Expired control material
- Low ambient temperature in the lab
Correct answer: Insufficient sample volume or presence of a fibrin clot in the sample
Clot detect errors are most commonly caused by insufficient sample volume or fibrin strands/microclots in the specimen that interfere with the optical or mechanical clot detection system.
CABT Laboratory Equipment 5
Which error in a clinical laboratory water purification system would most directly affect enzyme assays performed that day?