CMLA Quality Control & Assurance in Laboratory Practices 5 — Questions and Answers
Question 1: Which concept describes the maximum allowable difference between a test result and the true value, combining both systematic and random error?
- Analytical sensitivity
- Total allowable error (TEa) (Correct answer)
- Analytical specificity
- Predictive value positive
Correct answer: Total allowable error (TEa)
Total allowable error (TEa) defines the maximum acceptable combination of bias and imprecision, used as the quality goal for a laboratory method.
Question 2: A laboratory receives a proficiency testing challenge with five specimens. Under CLIA, how many must be reported to avoid a potential PT failure?
- At least three of five (60%) (Correct answer)
- At least four of five (80%)
- All five (100%)
- At least two of five (40%)
Correct answer: At least three of five (60%)
CLIA requires at least 80% satisfactory results on a PT challenge, but since graded on a score basis, typically 4/5 or 3/5 passing meets requirements depending on analyte-specific criteria.
Question 3: What is the correct interpretation when a Levey-Jennings chart shows control values scattered randomly above and below the mean with large variability?
- The method has acceptable systematic error only
- The method has a random error problem (Correct answer)
- The method is performing optimally
- The method has calibration drift
Correct answer: The method has a random error problem
Wide, random scatter of control values above and below the mean indicates random error, often caused by pipetting inconsistencies, temperature fluctuations, or unstable reagents.
Question 4: Which corrective action is most appropriate when a single control value fails the 1-3s rejection rule?
- Continue patient testing while noting the failure in the logbook
- Stop patient testing, investigate the cause, and repeat QC before reporting results (Correct answer)
- Repeat only the failed control and average the two results
- Adjust the mean on the Levey-Jennings chart to accommodate the outlier
Correct answer: Stop patient testing, investigate the cause, and repeat QC before reporting results
A 1-3s violation is a rejection rule requiring the laboratory to stop reporting, identify the root cause, resolve the issue, and confirm QC is acceptable before continuing.
Question 5: Which of the following is NOT a component of a laboratory quality assurance (QA) program?
- Proficiency testing
- Personnel competency assessment
- Patient result billing accuracy (Correct answer)
- Turnaround time monitoring
Correct answer: Patient result billing accuracy
Billing accuracy is a compliance and revenue cycle function, not a component of the laboratory quality assurance program focused on analytical and clinical quality.
Question 6: When establishing a new QC mean and standard deviation for a control material, the minimum number of data points typically recommended is:
- 5 data points over 2 days
- 10 data points over 5 days
- 20 data points over 20 days (Correct answer)
- 3 data points from a single run
Correct answer: 20 data points over 20 days
At least 20 data points collected over 20 days is the standard recommendation to establish a reliable mean and standard deviation for QC materials.
Question 7: A delta check compares a patient's current laboratory result to their previous result. Its primary purpose is to:
- Monitor reagent lot-to-lot variability
- Detect specimen identification or pre-analytical errors (Correct answer)
- Set new QC acceptance limits
- Verify calibrator traceability to a reference method
Correct answer: Detect specimen identification or pre-analytical errors
Delta checks flag unexpectedly large changes between sequential patient results, most commonly caused by wrong-patient specimens or sample misidentification.
CMLA Quality Control & Assurance in Laboratory Practices 5
Which concept describes the maximum allowable difference between a test result and the true value, combining both systematic and random error?