HCV core antigen testing in HIV- and HBV-coinfected patients, and in HCV-infected patients on hemodialysis.

BACKGROUND: A quantitative HCV core antigen (HCVcoreAg) immunoassay has been developed for the confirmation of viremia in patients with hepatitis C.

OBJECTIVES: We evaluated the correlation of HCV RNA and HCVcoreAg in different patient populations without HCV-specific treatment: HIV/HCV-coinfection, HBV/HCV-coinfection, and patients with end-stage renal disease.

STUDY DESIGN: HCVcoreAg was quantified by a fully-automated immunoassay. Correlation of HCVcoreAg with HCV RNA was studied cross-sectionally in HIV/HCV- and HBV/HCV-coinfected patients, as well as before and after hemodialysis in patients with end-stage renal disease.

RESULTS: A concordant positive or negative test result for both HCV RNA and HCVcoreAg was observed in 68 of 71 (96%), 55 of 57 (96%), and in 109 of 109 (100%) samples of patients with HIV- or HBV/HCV-coinfection, and patients undergoing hemodialysis, respectively. HCVcoreAg showed high correlation with HCV RNA in samples from HIV/HCV-coinfected patients and HCV-infected patients undergoing hemodialysis (r=0.97 and r=0.94, p<0.001). There was no overall correlation between HCVcoreAg and HCV RNA in HBV/HCV-coinfected individuals (r=0.04, p=0.822). Excluding patients with HCV RNA to HCVcoreAg ratios below 100 and above 10,000kIU/fmol led to improved correlation (r=0.53; p=0.02), but remained worse than for the other cohorts. Overall, HCV RNA to HCVcoreAg ratios did not differ significantly between the different patient populations, though variation tended to be higher in HBV/HCV-coinfected patients. Patients with lower HCV RNA levels tend to have lower HCV RNA/HCVcoreAg ratios.

CONCLUSIONS: HCVcoreAg represents a reliable marker of viral replication showing a good correlation with HCV RNA in various patient populations, with some limitations in HBV/HCV-coinfection.