A shift after a reagent change
A chemistry laboratory introduces a new reagent lot after the required incoming checks. During subsequent routine work, several control values shift to the same side of the established mean. One measurement now crosses the laboratory’s specified rejection boundary. The technician proposes averaging that value with earlier controls and continuing to report patient results. Maintenance and calibration records are available, but no cause has been established. The responsible staff must follow the actual rejection and investigation process, assess which results may be affected and avoid erasing evidence by repeated unrecorded reruns. This scenario does not prescribe one universal control rule or prove that the reagent lot is necessarily defective.
1. What action is justified?
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Hold affected reporting as required by the actual quality plan, investigate relevant reagent, calibration, instrument and process factors and document corrective action before restoring a valid system.
2. What does the shift prove?
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It suggests a changed analytical process and warrants investigation, but does not uniquely identify the reagent lot or another physical cause. Earlier controls cannot be averaged to cancel a rejection without a justified procedure.