Medical Laboratory Technician Exam Laboratory Operations and Safety 2 — Questions and Answers
Question 1: In a Levey-Jennings chart, which Westgard rule flags a run when one control value exceeds the mean by more than 3 standard deviations?
- 1-2s
- 1-3s (Correct answer)
- 2-2s
- R-4s
Correct answer: 1-3s
The 1-3s Westgard rule is a rejection rule triggered when a single control measurement exceeds ±3 SD from the mean.
Question 2: Which type of error causes all quality control results to shift in the same direction over time?
- Random error
- Systematic error (Correct answer)
- Gross error
- Blunder error
Correct answer: Systematic error
Systematic error produces a consistent directional shift or trend in QC values and is often caused by reagent deterioration or calibration drift.
Question 3: A laboratory's proficiency testing (PT) result for glucose is graded as unacceptable. What is the required next step under CLIA?
- Repeat the PT sample on a different instrument
- Perform an investigation and implement corrective action (Correct answer)
- Report the result to CMS within 24 hours
- Discontinue glucose testing until the next PT event
Correct answer: Perform an investigation and implement corrective action
CLIA requires laboratories to investigate the cause of an unacceptable PT result and document corrective actions taken.
Question 4: Which type of pipette delivers its nominal volume from tip drainage and is identified by a frosted or etched band near the top?
- TD (to deliver) pipette (Correct answer)
- TC (to contain) pipette
- Mohr pipette
- Pasteur pipette
Correct answer: TD (to deliver) pipette
TD (to deliver) pipettes are calibrated so that the volume drains out and the frosted band indicates no rinsing is needed to deliver the full volume.
Question 5: What is the purpose of a delta check in the laboratory?
- To verify instrument calibration
- To compare a patient's current result to a previous result (Correct answer)
- To evaluate interlab proficiency testing performance
- To check reagent lot-to-lot consistency
Correct answer: To compare a patient's current result to a previous result
A delta check compares a patient's current laboratory result to their prior result to detect specimen identification errors or unexpected clinical changes.
Question 6: Which tube color is used for serum chemistry testing because it contains a clot activator and gel separator?
- Lavender/purple
- Green
- Gold/SST (Correct answer)
- Light blue
Correct answer: Gold/SST
Gold or SST (serum separator tube) tubes contain a clot activator and gel separator that isolates serum after centrifugation for chemistry testing.
Medical Laboratory Technician Exam Laboratory Operations and Safety 2
In a Levey-Jennings chart, which Westgard rule flags a run when one control value exceeds the mean by more than 3 standard deviations?