Decision on conducting HCV Immunoblot and HCV Viral Load Tests Dependent upon the Result of the Screening Tests

Abstract

Testing for the presence of antibody to hepatitis C virus (anti-HCV) is recommended for initially identifying persons with HCV infection. According to the CDC guidelines it is appropriate to use a signal-to-cut-off value (S/CO) to limit the number of samples that needs supplemental testing. Moreover, the use of quantitative PCR assays for HCV RNA testing is fundamental for the assessment of chronic hepatitis C. The purpose of this study is to determine a specific value for a serological test for anti-HCV with a Positive Predictive Value (PPV) of 95% on positive HCV Immunoblot, and also determine a cut-off value for performing a clinically relevant HCV PCR. Were observed 415 individuals identified de novo as anti-HCV reactive, between 2009 and 2011. We estimate that a S/CO of 6.0 has a PPV of 99.83% being positive Immunoblot assay and that 99.49% of the samples with a S/CO ≤6.0 will have no detectable virus on PCR. Based on these results we propose a new algorithm for evaluation persons identified de novo as anti-HCV reactive: Immunoblot assay needs to be performed only for samples with a S/CO ≤6.0 and HCV PCR will be performed for persons with a S/CO >6.0. Using these criteria it would be possible to save € 9,000/year with acceptable clinical accuracy. This algorithm does not apply to rare cases of suspected acute HCV infection or suspicion of HCV infection in immunocompromised patients; for these cases we maintain the current approach of NAT testing for laboratory diagnosis of HCV infection.