The investigation determined that a lower than expected sodium result was obtained from a college of american pathologists proficiency sample processed using vitros chemistry products na+ slides lot 4241-1072-7737 on a vitros 5600 integrated system.The assignable cause of the lower than expected vitros na+ result is a suboptimal calibration.The parameters from the calibration used to obtain the lower than expected proficiency sample results were atypical when compared to the database values.Additionally, results from vitros performance verifiers were acceptable using the previous calibration prior to the event but were lower than expected using the suboptimal calibration parameters.Following a recalibration event, quality control results returned to expectations.In addition, the customer reprocessed the proficiency fluids after the recalibration event and the results were acceptable.The cause of the suboptimal calibration is unknown.It is unknown if the customer prepared the calibrators as directed or how the calibrators were handled prior to the calibration event on (b)(6) 2022.Calibrator fluid preparation or handling is a possible contributor of the suboptimal calibration, however it could not be confirmed nor ruled out.Although precision testing was not performed on the vitros 5600 integrated system an instrument related issue is not a likely contributor of the event as historical quality control results were precise.Additionally, results were returned to expectations after a recalibration event without any known troubleshooting actions being performed on the instrument.Continual tracking and trending of complaint data has not identified any signals to suggest there is a systemic quality issue with vitros na+ reagent lot 4241-1072-7737.
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