Evaluation of the Roche Cobas HCV immunoassay
Abstract number: P2018
Murk J.L.A.N., Simoons-Smit A.M., Savelkoul P.H.M., Bosschieter-Lust M., Ang C.W.
Objectives: The low prevalence of Hepatitis C virus (HCV) in developed countries places large demands on the specificity of immunoassays detecting antibodies to the HCV. Frequent false-positive test results have necessitated costly and time consuming confirmatory tests. We have evaluated the performance of the new HCV immunoassay for the Roche Cobas e411 automated analyzer and compared it with the HCV immunoassay version 3.0 from Abbott for the AxSYM automated analyzer.
Methods: 917 human sera, submitted to our laboratory as part of the routine diagnostic process for HCV testing, were analyzed with the immunoassays for the Cobas and AxSYM. 437 of these sera were tested in parallel between September and December 2008.
480 sera had been submitted previously (retrospective samples) and already been tested in the AxSYM. Anti-HCV reactivity was confirmed by immunublot or additional testing for HCV RNA.
Results: Of the 917 sera 68 tested positive in the AxSYM; 33 of these were immunoblot or HCV-PCR positive and 7 sera had equivocal immunoblots. The remaining 27/68 (40%) of initially reactive samples were regarded as false-positive. The specificity of the AxSYM HCV assay was therefore (848/876=) 96.8%. Out of 917 sera, the Cobas tested 46 sera positive. 33 were confirmed and 7 had equivocal immunoblots. Hence, 5/45 (11%) of the initially reactive samples could not be confirmed and were regarded as false-positive. The specificity of the Roche assay was (871/876=) 99.3%. Both AsXYM and Cobas HCV immunoassay detected all 33 confirmed cases of HCV infection.
Conclusion: The specificity of the new Roche HCV assay was higher than the Abbott HCV immunoassay and reduced the amount of confirmatory tests with about one third, although the difference may have been caused by selection of samples initially reactive on the AxSYM. Further parallel studies with larger numbers of samples from patients who are HCV positive are required to solve this issue.
|Session name:||19th European Congress of Clinical Microbiology and Infectious Diseases|
|Location:||Helsinki, Finland, 16 - 19 May 2009|
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