MLS Quality & Safety 2 — Questions and Answers
Question 1: A laboratory receives a proficiency testing (PT) sample and the result is flagged as 'unacceptable.' What is the most appropriate immediate action?
- Repeat the test on the same analyzer and report the average
- Investigate the root cause and document corrective action (Correct answer)
- Contact the PT provider to request a replacement sample
- Exclude the result and report the next PT cycle instead
Correct answer: Investigate the root cause and document corrective action
Unacceptable PT results require root cause investigation and documented corrective action per CLIA and accreditation standards.
Question 2: Which statistical term describes the degree to which repeated measurements of the same sample yield the same result?
- Accuracy
- Precision (Correct answer)
- Sensitivity
- Specificity
Correct answer: Precision
Precision (reproducibility) refers to the closeness of repeated measurements to each other, independent of the true value.
Question 3: A CBC analyzer's WBC results are consistently 15% higher than expected based on the reference method. This error is best described as:
- Random error
- Proportional systematic error (Correct answer)
- Constant systematic error
- Gross error
Correct answer: Proportional systematic error
Proportional systematic error increases with analyte concentration, producing a consistent percentage deviation from the true value.
Question 4: When performing a Levey-Jennings chart review, which Westgard rule is violated when one control value exceeds the mean by more than 3 standard deviations?
- 1-2s warning rule
- 1-3s rejection rule (Correct answer)
- 2-2s rejection rule
- R-4s rejection rule
Correct answer: 1-3s rejection rule
The 1-3s rule is a rejection rule triggered when a single control value falls outside ±3 SD, indicating probable random or systematic error.
Question 5: A chemical spill of sulfuric acid occurs in the chemistry lab. The FIRST action the MLS should take is:
- Neutralize the spill with sodium bicarbonate
- Evacuate the entire building
- Don appropriate PPE before approaching the spill (Correct answer)
- Call the facility safety officer before doing anything
Correct answer: Don appropriate PPE before approaching the spill
Personal protective equipment must be donned before approaching any chemical spill to protect the MLS from exposure.
Question 6: Which type of quality control material is most appropriate for monitoring day-to-day analytical performance on a chemistry analyzer?
- Patient samples from the previous day
- Commercially prepared assayed controls with known target values (Correct answer)
- Pooled patient sera without assigned values
- Calibrators provided by the manufacturer
Correct answer: Commercially prepared assayed controls with known target values
Commercially prepared assayed controls with established target ranges allow objective monitoring of analytical performance against known values.
Question 7: According to OSHA's Bloodborne Pathogens Standard, which item must be available to laboratory personnel who have occupational exposure to blood?
- N95 respirator fitted annually
- Hepatitis B vaccination at no cost (Correct answer)
- Annual TB skin testing
- Powered air-purifying respirator (PAPR)
Correct answer: Hepatitis B vaccination at no cost
OSHA's Bloodborne Pathogens Standard requires employers to offer hepatitis B vaccination free of charge to all employees with occupational blood exposure.
MLS Quality & Safety 2
A laboratory receives a proficiency testing (PT) sample and the result is flagged as 'unacceptable.' What is the most appropriate immediate action?