CLT Quality Control & Assurance in Testing 2

Question 1

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?

Accepted Answer

10x rule

Answer

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.

Question 2

Which of the following BEST describes 'accuracy' in laboratory quality control?

Accepted Answer

How close a measured value is to the true value

Answer

Accuracy refers to how closely a measured result agrees with the true or accepted reference value.

Question 3

A new reagent lot is being validated. QC results show acceptable precision but a consistent positive bias. What is the MOST appropriate corrective action?

Accepted Answer

Recalibrate the instrument using the new lot

Answer

A consistent positive bias indicates a systematic error that can often be corrected by recalibrating the instrument with the new reagent lot.

Question 4

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:

Accepted Answer

8 mg/dL — method is acceptable

Answer

Total error = bias + 2SD = 3 + 5 = 8 mg/dL, which is within the TEa of 10 mg/dL, so the method is acceptable.

Question 5

Which statistical measure is MOST useful for comparing the variability of two analytes with different units or concentration ranges?

Accepted Answer

Coefficient of variation (CV%)

Answer

The coefficient of variation expresses SD as a percentage of the mean, allowing comparison of variability across different analytes and concentration ranges.

(CLT) Clinical Laboratory Technologist Certification Practice Test

(CLT) Clinical Laboratory Technologist Certification Practice Test

CLT Quality Control & Assurance in Testing 2