[Low positive anti-HCV microparticle enzyme immunoassay results: do they predict hepatitis C virus infection?].

Antibody screening tests for hepatitis C virus (anti-HCV) can yield false positive results among populations such as Turkey, with a low prevalence of HCV infection. This may lead to the unnecessary use of expensive tests like HCV RNA for confirmation. However, HCV RNA is not always positive in samples with low S/Co (signal to cutoff) ratios. This retrospective study was conducted to determine the frequency of HCV RNA positivity in the samples with low anti-HCV levels. A total of 655 patients who were positive for anti-HCV by microparticle enzyme immunoassay (MEIA; v 3.0, AxSYM System, Abbott Laboratories, USA) and positive for HCV RNA by real-time polymerase chain reaction (PCR; iCycler IQ, v 3.0a, Bio Rad Laboratory, USA) between June, 2002 and November, 2005 were evaluated. Anti-HCV positivity was found in 368 (56%) patients and HCV RNA was not detected in samples with S/Co ratios lower than 3.8. As a result, for the confirmation of the samples yielding low and/or indeterminate grey zone anti-HCV levels, immunoblot methods, retesting of the same sample with another enzyme immunassay or testing of a new sample, would be appropriate and economical prior to use of HCV RNA tests.