CLC Data Analysis & Reporting Techniques 2 — Questions and Answers
Question 1: A laboratory receives results with a coefficient of variation (CV) of 18% for a quality control sample where the acceptable limit is 10%. What is the most appropriate corrective action?
- Report results with a disclaimer
- Investigate calibration, reagents, and instrument performance before releasing results (Correct answer)
- Average the QC results with the previous run
- Increase the number of patient samples to dilute the outlier
Correct answer: Investigate calibration, reagents, and instrument performance before releasing results
A CV exceeding the acceptable limit indicates imprecision, requiring root-cause investigation of calibration, reagents, and instrument performance before results can be released.
Question 2: Which statistical method is most appropriate for detecting a gradual upward drift in a laboratory's daily QC values over a two-week period?
- Westgard 1-3s rule
- Linear regression trend analysis (Correct answer)
- Youden plot comparison
- Chi-square test
Correct answer: Linear regression trend analysis
Linear regression trend analysis is used to detect systematic directional drift in QC data over time by modeling the slope of the data series.
Question 3: In laboratory reporting, a delta check flags a patient's sodium result as 168 mEq/L compared to 138 mEq/L three days prior. What is the primary purpose of this flag?
- To identify analytically erroneous results or specimen mix-ups by comparing sequential patient values (Correct answer)
- To alert clinicians of a life-threatening critical value
- To trigger automatic repeat testing at no charge
- To document a billing discrepancy
Correct answer: To identify analytically erroneous results or specimen mix-ups by comparing sequential patient values
Delta checks compare current results to previous results for the same patient to detect specimen mix-ups, transcription errors, or analytical errors.
Question 4: A lab consultant is reviewing a Levey-Jennings chart and notices 10 consecutive QC points all falling on the same side of the mean. Which Westgard rule is violated?
- 1-2s warning rule
- R-4s rule
- 10-x rule (Correct answer)
- 2-2s rule
Correct answer: 10-x rule
The 10-x rule is triggered when 10 consecutive QC measurements fall on the same side of the mean, indicating systematic bias.
Question 5: When preparing a laboratory performance report for hospital administration, which metric best demonstrates the laboratory's contribution to patient throughput?
- Total reagent consumption per month
- Turnaround time (TAT) from order to result (Correct answer)
- Number of QC failures per quarter
- Percentage of tests outsourced to reference labs
Correct answer: Turnaround time (TAT) from order to result
Turnaround time directly reflects how quickly the laboratory delivers actionable results, making it the key metric for demonstrating contribution to patient care throughput.
Question 6: A CLC is asked to validate a new automated hematology analyzer. Which statistical comparison is most appropriate for method correlation?
- Passing-Bablok regression (Correct answer)
- Kaplan-Meier survival analysis
- Receiver operating characteristic (ROC) curve
- Analysis of variance (ANOVA)
Correct answer: Passing-Bablok regression
Passing-Bablok regression is a non-parametric method used for method comparison that is not affected by outliers or non-normally distributed data.
Question 7: In an external proficiency testing (PT) program, a laboratory's result falls more than 3 standard deviations from the peer group mean. What is the required response?
- Document the result and continue without action
- Perform a root-cause investigation and submit a corrective action plan (Correct answer)
- Resubmit a corrected value to the PT provider
- Withdraw from the PT program for that analyte
Correct answer: Perform a root-cause investigation and submit a corrective action plan
An unacceptable PT result requires a formal root-cause investigation and corrective action plan to identify and resolve the source of the error.
CLC Data Analysis & Reporting Techniques 2
A laboratory receives results with a coefficient of variation (CV) of 18% for a quality control sample where the acceptable limit is 10%.
What is the most appropriate corrective action?