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A customer in (b)(6) notified biomérieux of false positive results associated with bact/alert® 3d instrument.The customer reported that when the bottles flagged positive by the instrument the laboratory performed a subculture using bold macconkey, chocolate agar incubating the plates +/- co2 at 37°c for 48 h.The customer reported that the concerned bottles were unloaded and incubated further in the external incubator together with the subcultures.If there was no growth on the subculture after 48 hours, the laboratory inoculated another sample from the bottle and incubated it again for 48 hours.This step has been repeated until the end of the incubation time defined for the bottles (seven days).Patient results: false positive result.Delay in reporting of results.The bact/alert results have been released to the physician, when the bottles were flagged positive.After having the subculture results, the customer informed the physician about the false positive results.There is no evidence regarding inappropriate patient treatment.An internal biomérieux investigation will be initiated.
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An internal biomérieux investigation was performed with results as follows: backup review for bottle id - arrhsbvm - the bottle was loaded in cell1a13 when the instrument determined the initial positive result.The bottle was reloaded in cell 2a12 after the positive event.The dip in the graph is caused when the bottle is reloaded after the first positive event, this is normal.There is no final result listed for the bottle as it was still under test when the backup was created.Table 1: bottle history (b)(6) algorithm results graphs arrhsbvm - the instrument determined the bottle result was positive by (res pos how 1 "rate") as shown in the table above.The bottle readings were processed through the bact algorithm tool which determined the same result "rate" as the instrument.Fault codes - there were no fault codes recorded on the system during the time the bottle was under test from (b)(6) 2018 when the instrument flagged the bottle positive in cell location 1a13 for incubation module 1.There were no temperature or power events recorded on the system.There were no fault codes that were recorded on the system and no impact on the bottle testing or result.Operator error - there is one operator error code recorded during the testing time.The operator error code that was recorded on the system are detailed below had no impact on the bottle testing or result.Operator error code 800 - printer fault bottle loading and unloading events the backup shows the customer does not load or unload a large numbers of bottles at once from the instrument.Large loading and unloading events can cause a heat loss within the racks.Sample issue - the customer stated that the white blood cell count [wbc] is 3760, which is considered normal.The fill volume was not verified by the customer as the bottles were no longer available.Conclusion the backup was reviewed from the site, there were no bottle movements, fault / operator codes, or algorithm issues found with the instrument that caused the false positives to occur.The backup did show that the customer loaded multiple bottles (10 bottles) in the rack which could cause a drop in temperature; however temperature fault codes did not occur, therefore, loading multiple bottles can be ruled out as a root cause.To prevent possible temperature fluctuations, the customer should activate the cold bottle compensation filter (see 514483-8en1 setup and configuration version b.50) to alleviate potential false positives when loading and unloading in bulk.Currently, the backup shows this feature is disabled.The probable root cause is sample related as all known issues with the instrument have been reviewed and not determined to be the root cause of the false positives.Biomérieux recommends to review the best practices in the user manual 514818 appendix c to help prevent false positives with the instrument and sample.Also recommend to follow the ifu (instructions for use) when handling false positives.
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