A customer in the united kingdom notified biomérieux of obtaining false positive results in association with the bact/alert® mp (ref 419744, lot 1053174).The customer stated that after a recent preventive maintenance was performed, 17 bottles were flagged as positive.Six (6) of the bottles were either contaminated or actually positive while 11 were false positive.The customer stated that there was no patient impact due to the false positive results.Biomérieux will initiate an internal investigation.
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This report was initially submitted following notification from a customer in the united kingdom regarding false positive results in association with the bact/alert® mp (ref (b)(4), lot 1053174).The customer stated that after a recent preventive maintenance (pm) was performed, (b)(4).No organisms were present on the smear and subculture; however, the customer obtained false positive results.The investigation did not find the root cause for the bact/alert® mp bottle increased instrument false positive rate to be related to the bact/alert® mp bottle lot or the 3d instrument pm (preventive maintenance).Performing the instrument pm should not cause an increase in delta algorithm false positives.In fact, the proactive cell calibrations performed by the field service engineer (fse) should help reduce any such issue.The occurrence of instrument false positive bottles with no organisms present is a known risk for the test per the bact/alert® mp bottle¿s instructions for use (ifu).The impact to patient is low, as the confirmatory smear and subculture show no mycobacteria are present.The bact/alert 3d backup provided data generated right before the pm, so did not contain the events of interest to this complaint case.However, evaluation of data in the backup did provide some guidance for why increased instrument false positives occurred.Most of the false positive-looking graphs flagged positive by the delta algorithm; therefore, it is possible the sample pellet ph was out of range.If the customer is using a higher percentage of naoh or using the oxalic acid method, the ph is more likely to be an issue.The customer moved the mp bottles after first loading, and this could have contributed to a delta false positive.Some graphs were noisy, which could relate to temperature changes in the room where the instrument is located.The customer loads and unloads bottles in smaller batch sizes, which reduces excessive temperature changes from user activity.Loading pattern is not a likely contributor.No pattern by cell location was identified.Lastly, some of the reloaded positive mp bottles generated true positive graphs.This could indicate the customer is not finding the organism on the smear from the positive bottle.The organism may be washing off the slide during the staining procedure.The following are possible root causes that can cause an instrument false positive result for bact/alert® mp bottle, where no organisms are present.It is possible that multiple root causes are contributing to an increase in false positives.Room temperature variation where the instrument is located.Sample ph outside range of 6.8 to 7.2.Adding more than 0.5 ml of supplement, which can make the bottle more acidic.Add exactly 0.5 ml (measured) of supplement so that media has pink tinge.Adding more than 0.5 ml of the patient¿s sample to the mp bottle.Moving mp bottles after they are first loaded, which can change reflectance and cause the delta algorithm to trigger a positive.Loading and unloading bottles in large batches that creates a temperature change in the drawer, which in turn causes dips in the graph due to the temperature changes can trigger a positive by the acceleration algorithm.Improper storage of mp bottles part 419744 by refrigeration or in direct sunlight.Failure to mix bottle by inversion prior to loading on instrument.Review of the manufacturing records showed that the bact/alert® mp culture bottle lot 1053174 met all quality control and release criteria.No malfunctions with the bottle lot, or adverse complaint trends were found.The investigation did not find the bact/alert® bottle lot 1053174 or the bact/alert® 3d instrument was the root cause for the complaint issue.Biomérieux will continue to monitor similar complaints for this issue.
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