The investigation determined that lower than expected vitros psa results were attained from two different patient samples using vitros immunodiagnostics products psa (psa) reagent in combination with a vitros 5600 integrated system.The results were lower then expected when compared to the results obtained from the same samples freshly drawn.A definitive assignable cause for the low results could not be determined.Based on historical quality control results, a vitros psa lot 3620 and 3640 performance issue is not a likely contributor to the event.Continual tracking and trending of complaints has not shown any existing signals that would point to a potential systemic issue with vitros immunodiagnostics products psa (psa) reagent lot 3620 or 3640.In addition, there is no indication of an instrument malfunction.However, a within run precision test was not run at the time of the event and therefore, an instrument issue cannot be definitively ruled out.Furthermore, pre-analytical sample processing cannot be ruled out as a contributing factor, as it was not possible to establish if the customer was following the sample collection device manufacturer¿s recommendation for sample centrifugation.It is possible that cellular debris, due to poor sample preparation, was present in the affected samples, although this could not be confirmed.Additionally, when samples are tested concurrently, reproducible results are obtained for both fresh and stored samples using both reagent lots.Only when fresh samples are compared to stored samples are biased results observed.Consequently, sample preparation and the handling and storage of the samples cannot be ruled out as a contributing factor to the event.
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