Quantitative assays for hepatitis C virus in serum as predictors of the long-term response to interferon

Background/Aims: Interferon therapy has a beneficial effect in patients with chronic hepatitis C who have a low viral load. The aim of this study was to compare the core protein level with HCV RNA levels and to analyze whether virus quantitation predicts the efficacy of interferon therapy. Methods: HCV core protein level assessed by the recently developed assay was compared with HCV RNA levels measured by three different methods (Amplicor-HCV monitor, competitive RT (CRT)-PCR, and bDNA probe assay) in 352 patients with chronic hepatitis C in relation to viral serotype. Results: From 91% (320/352) to 93% (299/322) of patients with viremia were detected by Amplicor- monitor and CRT-PCR, in contrast to 60% (187/312) and 74% (191/258) by bDNA and HCV core protein assay, respectively. The HCV core protein level was positively correlated with HCV RNA levels measured by the three assay (r=0.680 to 0.731). Serum HCV RNA and core protein levels were significantly lower in patients with serotype 2 than in those with serotype 1. Viral eradication after interferon therapy was observed in 60–70% of the patients with <1 × 104 copies/ml of HCV RNA by Amplicor-monitor assay, <2 × 105 copies/ml by CRT-PCR, <0.5 Meq/ml by bDNA assay, and <20 pg/ml of core protein by HCV core protein assay. Viral eradication was uncommon (<11%) among the patients with higher viral loads. Bivariate analysis revealed that the outcome of interferon therapy was more closely associated with both HCV core protein and RNA levels than the HCV serotype. Conclusions: Quantitation of HCV core protein and HCV RNA is useful for prediction of the interferon response.