What is the first step when you observe drift in a control value over several days?

• A. Document and ignore
• B. Recalibrate immediately without investigation
• C. Re-run patient results
• D. Investigate root cause

Answer: (D)

When you see drift in a control value over several days, the first step is to investigate the root cause. A drift indicates a potential systematic problem that could affect patient results if left unaddressed, so you don’t jump to recalibration or re-testing patients until you understand what changed. Begin by reviewing recent changes and data: instrument calibration status and maintenance logs, reagent lots and expiry, calibration materials, software updates, and environmental conditions (temperature, humidity). Examine the control chart to see the pattern and confirm the drift is real and not a random fluctuation. If possible, retest the control materials to verify the issue and trace it to a likely source. Only after identifying and addressing the underlying cause should you take corrective actions such as recalibration or replacing reagents. Document the investigation and actions taken to prevent recurrence.