How is bias assessed in proficiency testing, and what does it inform?

How is bias assessed in proficiency testing, and what does it inform?

• A. Compare lab results to reference true values; assess mean difference
• B. Compare to peer laboratories' averages
• C. Use internal precision only
• D. Ignore results and continue

Answer: (A)

Bias is about a systematic deviation from the true value. In proficiency testing, a reference (true) value is assigned to each sample, and the lab’s result is compared to that value. The difference between the lab result and the reference (often expressed as a mean or percent difference) shows whether there is a consistent over- or under-estimation—i.e., bias. This information reveals the accuracy of the measurement approach and indicates whether calibration, method verification, or other corrective actions are needed to remove that systematic error. While comparing to peer laboratories might show relative performance, it doesn’t quantify how far results are from the true value. Focusing only on internal precision measures variability, not accuracy. Ignoring results would miss opportunities to improve reliability.

Bias is about a systematic deviation from the true value. In proficiency testing, a reference (true) value is assigned to each sample, and the lab’s result is compared to that value. The difference between the lab result and the reference (often expressed as a mean or percent difference) shows whether there is a consistent over- or under-estimation—i.e., bias. This information reveals the accuracy of the measurement approach and indicates whether calibration, method verification, or other corrective actions are needed to remove that systematic error. While comparing to peer laboratories might show relative performance, it doesn’t quantify how far results are from the true value. Focusing only on internal precision measures variability, not accuracy. Ignoring results would miss opportunities to improve reliability.