A customer in the united states reported a performance problem with nuclisens® magnetic silica when extracting urine samples on the easymag® instrument for two patients (a & b).The customer stated that results for the same patient when tested at different volumes, gave really different results downstream.The downstream application was run as a quantitative assay for bk virus.The customer ran the test on patient a in duplicate.The extraction was performed two different ways, they first ran the urine in duplicate for a volume of 500 ¿l with an eluate of 60¿l and the second was 200 ¿l with an eluate of 50 ¿l.Downstream for bk virus they recovered a result of 4.3 million for the sample that had 500 ¿l volume and they obtained 26000 for the 200 ¿l volume sample.For patient b the customer also ran this in duplicate and they reported that they first ran the urine in duplicate for a volume of 500 ¿l with an eluate of 60 ¿l and the second was 200 ¿l with an eluate of 50 ¿l.Downstream for bk virus they recovered a result of 8,000 for the sample that had 500 ¿l volume and they obtained 763,000 for the 200 ¿l volume sample.The customer reported that samples for patient a and b were sent to a reference lab at 3-4 days for results to be reported out.There was no wrong result reported to a physician, and the patient treatment was not impacted.There is no indication or report from the hospital or treating physician to biomérieux that the discrepant result led to any adverse event related to the patient's state of health.A biomérieux internal investigation will be initiated.
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An internal investigation was performed for an issue with nuclisens® magnetic silica (batch z019fe1ms) when extracting urine samples on the easymag® instrument for two patients.The customer stated that results for the same patient when tested at different volumes, were different for the downstream application which was run as a quantitative assay for bk virus.As the issue was potentially related to the presence of aggregates in the urine samples, biomérieux requested the samples from the customer.The samples were no longer available.Batch records were reviewed.Silica z019fe1ms used by the customer, is composed of the raw materials 01/18 a1227793 and 04/18 a1287993 and is thus the same as silica batches: z019fb1ms, z019fc1ms, z019fd1ms, z019ff1ms, z019fg1ms, z019fh1ms, and z019fk1ms.Functional tests were performed by r&d to check the stability of the silica batch z019fe1ms that s composed of the same raw material as silica z019fb1ms.There was no degradation tendency for this silica in the stability tests performed up to 8 months.Complaint history was reviewed for the magnetic silica ref 280133, batches z019fb1ms, z019fc1ms, z019fd1ms, z019fe1ms, z019ff1ms, z019fg1ms, z019fh1ms and z019fk1ms.Only this complaint was for the performance of batch z019fe1ms.One other complaint was for the performance of z019fb1ms and z019fc1ms.No trend was identified for batch z019fe1ms.Conclusion: nuclisens® magnetic silica (batch z019fe1ms) conformed to internal specifications and the stability results analysis showed no issue.There was only one other complaint for a performance issue amongst eight batches of silica composed of the same raw material.The issue could thus be assessed as an isolated case.The issue is highly suspected to be due to the quality of the samples themselves, which could contain aggregates trapping the viral particles.Urine samples are known to be subject to the presence of aggregates, which could trap the viral particles.Depending on the way the samples are processed (centrifugation, homogenization etc.), their content in viral particles may vary from test to test.The root cause could not be determined without the samples.
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