CLC Data Analysis & Reporting Techniques 3 — Questions and Answers
Question 1: A laboratory is implementing a new reporting format for critical values. Which element is most essential to include in the critical value notification documentation?
- The patient's insurance information
- The name of the person who received the notification and the time of notification (Correct answer)
- The cost of the test performed
- The analyst's personal opinion of the clinical significance
Correct answer: The name of the person who received the notification and the time of notification
Critical value notification documentation must include who received the report and the time, as this creates an auditable record of the communication loop.
Question 2: Which of the following best describes the purpose of a Bland-Altman plot in laboratory method validation?
- It ranks analytes by clinical importance
- It graphically displays the agreement between two measurement methods by plotting the difference against the mean (Correct answer)
- It identifies the optimal QC rule for a given assay
- It calculates the sensitivity and specificity of a diagnostic test
Correct answer: It graphically displays the agreement between two measurement methods by plotting the difference against the mean
A Bland-Altman plot visualizes the mean difference (bias) and limits of agreement between two methods, revealing whether they can be used interchangeably.
Question 3: A laboratory director requests a Six Sigma analysis of a glucose assay. The assay has a bias of 1.5% and a CV of 2.0%, with an allowable total error of 10%. What is the Sigma metric?
- 2.5
- 4.25 (Correct answer)
- 5.5
- 3.0
Correct answer: 4.25
Sigma = (TEa - |bias|) / CV = (10 - 1.5) / 2.0 = 8.5 / 2.0 = 4.25, indicating a good but improvable process.
Question 4: When calculating the predictive value of a positive test result in a low-prevalence population, which phenomenon must a CLC account for?
- The base rate fallacy (low PPV despite high sensitivity and specificity) (Correct answer)
- Regression to the mean
- The Hawthorne effect
- Simpson's paradox
Correct answer: The base rate fallacy (low PPV despite high sensitivity and specificity)
In low-prevalence populations, even highly sensitive and specific tests yield a low positive predictive value (PPV) because false positives outnumber true positives.
Question 5: A laboratory quality report shows a consistent inter-laboratory bias when comparing results with a reference method. This type of error is best classified as:
- Random error
- Systematic error (Correct answer)
- Blunder error
- Proportional random error
Correct answer: Systematic error
A consistent directional bias between a laboratory method and a reference method is a systematic error, affecting accuracy rather than precision.
Question 6: Which type of control chart is most appropriate for monitoring the proportion of laboratory specimens rejected due to hemolysis over time?
- Levey-Jennings chart
- p-chart (proportion chart) (Correct answer)
- Shewhart X-bar chart
- CUSUM chart
Correct answer: p-chart (proportion chart)
A p-chart is used to monitor the proportion or percentage of defective items (such as rejected specimens) over time in process control.
Question 7: A CLC is evaluating reference interval verification for a new patient population. According to CLSI EP28-A3c, what is the minimum recommended sample size for transference verification?
- 10 samples
- 20 samples (Correct answer)
- 40 samples
- 100 samples
Correct answer: 20 samples
CLSI EP28-A3c recommends a minimum of 20 reference individuals to verify that a manufacturer's reference interval is transferable to a new patient population.
CLC Data Analysis & Reporting Techniques 3
A laboratory is implementing a new reporting format for critical values.
Which element is most essential to include in the critical value notification documentation?