(b)(4).The investigation determined that discordant, higher than expected vitros anti- sars-cov-2 igg results were obtained from a single patient sample processed using vitros cov2igg reagent lot 0185 on a vitros 3600 immunodiagnostic system and a vitros xt7600 integrated system.The vitros cov2igg results were higher than expected when compared to vitros cov2tot results and non-vitros anti-sars-cov-2 results for the patient.A definitive assignable cause for the discordant reactive vitros cov2igg results could not be determined.A vitros cov2igg lot 0185 reagent issue cannot be ruled out as a contributor to the event as there was no evidence that quality control fluids had been run around the time of the event.However, ongoing tracking and trending of complaints has not identified any signals that would point to a potential systemic issue with vitros cov2igg lot 0185.There was no evidence to suggest an instrument malfunction, however an instrument issue cannot be ruled out as a contributor to the event, as no precision testing was conducted to verify the performance of the vitros 3600 immunodiagnostic system or the vitros xt7600 integrated system around the time of the event.An interferent that affects the vitros cov2igg reagent assay cannot be ruled out as a contributor to the event, as no testing to rule out interference was conducted.In addition, pre-analytical sample processing could not be ruled out as a contributing factor as it was not determined whether the customer was following the sample collection device manufacturer¿s recommendation for sample centrifugation.Improper pre-analytical sample handling could have contributed to this event.It is possible that cellular debris, due to poor sample preparation, was present in the affected sample, although this could not be confirmed.
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