Serum levels of hepatitis C virus core antigen as a marker of infection and response to therapy

OBJECTIVES: Hepatitis C virus (HCV) core antigen is a recently developed marker of hepatitis C infection. We compared the predictive power of HCV core antigen with reverse transcription polymerase chain reaction (RT-PCR) and branched DNA assay for HCV-RNA as markers of infection and response to interferon therapy. METHODS: Four hundred and forty-four sera from 111 patients (65 men, 52 yr) with chronic hepatitis C, receiving ribavirin together with standard interferon (n = 61) or pegylated interferon (n = 50) were retrospectively investigated. RESULTS: Pretreatment, RT-PCR, branched DNA (median 621,887 IU/ml), and HCV core antigen (median 57 pg/ml) gave positive results in 100%, 99%, and 94% of the sera; the correlation between HCV core antigen and branched DNA was 0.75. The median HCV RNA level among the 7 of 111 (6%) patients that had a negative core Ag result was 15,016 IU/ml. Pretreatment levels of HCV core antigen were significantly lower in the 41 patients with a sustained virological response than in the 39 relapsers and 31 nonresponders (17 pg/ml, 114 pg/ml, 58 pg/ml; p-value 0.005). Independently of treatment schedule, wk 12 more than 2 log(10) reduction of viremia or a negative result for HCV core antigen had 100% negative predictive value (NPV) for a response to therapy compared to 94% for negative RT-PCR. The positive predictive value (PPV) of HCV core antigen and branched DNA was only 47% and 48%. CONCLUSIONS: In conclusion, the HCV core antigen is a less sensitive test of HCV viremia than HCV-RNA assays and is competitive with the bDNA assay as an early predictor of a nonresponse.