Quality Control & Assurance in Testing Flashcards
7 cards from real CLT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Quality Control & Assurance in Testing flashcards as text
A laboratory's Levey-Jennings chart shows 6 consecutive QC values all falling on the same side of the mean. Which Westgard rule is violated?
Answer: 10x rule
The 10x rule is triggered when 10 consecutive QC values fall on the same side of the mean, indicating a systematic shift; 6 consecutive points triggers the 6x warning rule.
Which of the following BEST describes 'accuracy' in laboratory quality control?
Answer: How close a measured value is to the true value
Accuracy refers to how closely a measured result agrees with the true or accepted reference value.
A new reagent lot is being validated. QC results show acceptable precision but a consistent positive bias. What is the MOST appropriate corrective action?
Answer: Recalibrate the instrument using the new lot
A consistent positive bias indicates a systematic error that can often be corrected by recalibrating the instrument with the new reagent lot.
The total allowable error (TEa) for a glucose assay is ±10 mg/dL. If bias is 3 mg/dL and imprecision (2 SD) is 5 mg/dL, the method's total error is:
Answer: 8 mg/dL — method is acceptable
Total error = bias + 2SD = 3 + 5 = 8 mg/dL, which is within the TEa of 10 mg/dL, so the method is acceptable.
Which statistical measure is MOST useful for comparing the variability of two analytes with different units or concentration ranges?
Answer: Coefficient of variation (CV%)
The coefficient of variation expresses SD as a percentage of the mean, allowing comparison of variability across different analytes and concentration ranges.
A laboratory uses a peer-group comparison program where mean QC values are compared to other laboratories using the same method. This is an example of:
Answer: Interlaboratory comparison
Comparing QC data among laboratories using the same method and reagents is interlaboratory comparison, a form of external quality assessment.
When a QC result violates a warning rule but not a rejection rule, the BEST course of action is to:
Answer: Document the warning and proceed with caution, running additional QC
Warning rules signal increased probability of error; the run should not be automatically rejected but additional QC should be run and the situation documented.