CMLA Quality Control & Assurance in Laboratory Practices 2 — Questions and Answers
Question 1: When a control value falls outside the 2s warning limit but within the 3s rejection limit, which Westgard rule has been violated?
- 1-2s warning rule (Correct answer)
- 1-3s rejection rule
- R-4s rejection rule
- 2-2s rejection rule
Correct answer: 1-2s warning rule
The 1-2s rule is a warning rule triggered when one control value exceeds ±2 standard deviations, signaling the need for increased scrutiny.
Question 2: Which type of error causes all control values to shift consistently in the same direction from the mean?
- Random error
- Systematic error (Correct answer)
- Gross error
- Proportional error
Correct answer: Systematic error
Systematic error (bias) shifts results consistently in one direction, often due to reagent lot changes, calibration drift, or temperature issues.
Question 3: A laboratory's Levey-Jennings chart shows the last six consecutive control values trending steadily upward. Which Westgard rule does this violate?
- 1-3s rule
- 2-2s rule
- 10x rule (Correct answer)
- R-4s rule
Correct answer: 10x rule
The 10x rule is violated when 10 consecutive control values fall on the same side of the mean, indicating systematic bias.
Question 4: What is the primary purpose of running both normal and abnormal control levels in the laboratory?
- To reduce reagent waste
- To detect errors across the reportable range (Correct answer)
- To satisfy billing requirements
- To train new laboratory staff
Correct answer: To detect errors across the reportable range
Running controls at multiple levels ensures the method performs accurately across the entire clinically relevant range, not just at one concentration.
Question 5: Which document defines acceptable performance specifications for a laboratory test, including allowable total error?
- Delta check report
- Quality control chart
- Method validation protocol (Correct answer)
- Proficiency testing summary
Correct answer: Method validation protocol
A method validation protocol defines performance specifications such as precision, accuracy, and allowable total error before a test is implemented.
Question 6: If a laboratory's coefficient of variation (CV) for a glucose control is 3%, what does this indicate about the method's precision?
- High imprecision; the method needs recalibration
- Acceptable precision for most routine chemistry tests (Correct answer)
- Perfect precision with no variability
- Systematic bias requiring reagent replacement
Correct answer: Acceptable precision for most routine chemistry tests
A CV of 3% for glucose is generally within acceptable limits for routine chemistry, indicating adequate but not perfect precision.
Question 7: Which regulatory body sets proficiency testing (PT) requirements for laboratories under CLIA '88?
- The Joint Commission (TJC)
- Centers for Medicare & Medicaid Services (CMS) (Correct answer)
- College of American Pathologists (CAP)
- American Society for Clinical Pathology (ASCP)
Correct answer: Centers for Medicare & Medicaid Services (CMS)
CMS administers the CLIA program and sets mandatory proficiency testing requirements for laboratories performing moderate- and high-complexity testing.
CMLA Quality Control & Assurance in Laboratory Practices 2
When a control value falls outside the 2s warning limit but within the 3s rejection limit, which Westgard rule has been violated?