Irreproducible positive results on the Cobas AmpliPrep/Cobas TaqMan HIV-1 Qual test are qualitatively different from confirmed positive results

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dc.contributor.advisorVan Zyl, Gert Uvesen_ZA
dc.contributor.advisorPreiser, Wolfgangen_ZA
dc.contributor.authorMaritz, Jeanen_ZA
dc.date.accessioned2013-11-13T15:28:55Zen_ZA
dc.date.accessioned2014-02-07T07:28:56Z
dc.date.available2013-11-13T15:28:55Zen_ZA
dc.date.available2014-02-07T07:28:56Z
dc.date.issued2013-10en_ZA
dc.descriptionThe original publication is available at http://onlinelibrary.wiley.com/doi/10.1002/jmv.23811/fullen_ZA
dc.description.abstractCriteria that define low positive results on the COBAS® AmpliPrep/COBAS® TaqMan (CAP/CTM) HIV- 1 Qual test as inconclusive have been adopted by all academic centres in South Africa that conduct infant HIV PCR, following previous investigations that showed poor specificity of these results. Retesting all these specimens has considerable cost implications. It was therefore attempted to better characterise such inconclusive results, by comparing those that prove to be either negative or positive on follow-up testing. This retrospective, laboratory-based study found that 193 of 211 (91.5%) patients with with previous inconclusive results (defined as reported positive by CAP/CTM but with cycle threshold [Ct] values of >32 and/or fluorescence intensity [FI] values of <5) tested negative and only 18 (8.5%) positive using independently obtained follow-up samples after a median of 28 days). The only significant independent predictor of a later positive result was a higher FI value (3.326 vs. 0.495, p<0.0001), whereas Ct values were not independently predictive. Specimens from patients negative on follow-up testing were qualitatively different from specimens that proved to be true positive. As the lower FI values in false-positive compared to true-positive results are probably indicative of a non-specific signal, the incorporation of stringent amplification slope criteria in the assay’s test definition file may improve correct classification and thus reduce the need for repeat testing of a large number of inconclusive specimens.en_ZA
dc.format.extent19 p. : ill.
dc.identifier.citationMaritz, J., Van Zyl, G. U. and Preiser, W. 2013. Irreproducible positive results on the Cobas AmpliPrep/Cobas TaqMan HIV-1 Qual test are different qualitatively from confirmed positive results, Journal of Medical Virology, 86(1):82-87, doi: 10.1002/jmv.23811en_ZA
dc.identifier.issn1096-9071 (online)en_ZA
dc.identifier.otherdoi: 10.1002/jmv.23811en_ZA
dc.identifier.urihttp://hdl.handle.net/10019.1/86114
dc.language.isoen_ZAen_ZA
dc.subjectPCRen_ZA
dc.subjectInfant diagnosisen_ZA
dc.subjectFalse positiveen_ZA
dc.subjectLaboratory diagnosisen_ZA
dc.subject.otherDivision of Medical Virology, Department of Pathologyen_ZA
dc.titleIrreproducible positive results on the Cobas AmpliPrep/Cobas TaqMan HIV-1 Qual test are qualitatively different from confirmed positive resultsen_ZA
dc.typeArticle
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