How often must a laboratory analyze PT samples to maintain full certification for an analyte?

• A. At least once every 12 months for each analyte and by each method used to analyze compliance samples.
• B. Every 24 months.
• C. Once per analyte.
• D. Only when required by accrediting body.

Answer: (A)

Regular proficiency testing keeps a lab’s measurement practices honest over time. To maintain full certification for an analyte, the lab must demonstrate acceptable performance on PT samples for every analyte it reports and for every method it uses to analyze compliance samples. Doing PTs at least once each year ensures that any drift or bias in both the analyte and the method is detected early and corrected before it affects patient results or regulatory reporting. If PT is infrequent or limited to only some analytes, changes in method performance or the introduction of new methods may go unnoticed, risking noncompliance. The other approaches either extend the window too long, ignore variability between methods, or rely on external scheduling rather than ongoing, method- and analyte-specific verification.