What is the purpose of external proficiency testing in QA/QC programs?

What is the purpose of external proficiency testing in QA/QC programs?

• A. To check instrument calibrations.
• B. To benchmark performance against peer laboratories and verify ongoing accuracy.
• C. To accelerate sample throughput.
• D. To reduce maintenance costs.

Answer: (B)

External proficiency testing provides an independent benchmark of a lab's performance by comparing its results with those of other laboratories on blinded samples with known values. This benchmarking helps verify ongoing accuracy and reveals any drifts or biases over time, across different analysts, instruments, and methods. It’s a common requirement for accreditation because it demonstrates inter-lab comparability and overall competence.

It isn’t primarily about instrument calibrations (that’s handled by internal QC and calibration checks), nor is it designed to speed up sample throughput or reduce maintenance costs.