What happens inside a proficiency testing round

A proficiency testing round looks simple from the laboratory bench, but each step is designed so that every participant is judged fairly.

• Samples are distributed. Homogeneous samples go to all participating laboratories, packed for the destination and the expected transit time so everyone receives the same material.
• You test and submit. Results are returned to the provider, often through an online portal.
• The data is processed. The provider determines an assigned value, usually a median, mean or reference result, following the statistical protocol for the scheme.
• Performance is assessed. Each result is measured by how far it sits from the assigned value, and bias is tracked through rolling averages over time.
• You receive a confidential report. Only your laboratory sees your own performance.

Then the cycle repeats at an established frequency, so consistency as well as accuracy and precision can be judged over time. Many schemes also let several technicians, methods or instruments submit results, which turns a round into a training tool as well as a check.