The diagnostic significance of an assay for 'total' hepatitis C core antigen

A measurable serological response to hepatitis C infection is delayed on av erage until 70 days after infection. In addition, it may not occur in some immunocompromised people. Detection of free hepatitis C (HCV) core antigen in blood has enabled diagnosis in the pre-seroconversion period. The abilit y to detect 'total' HCV core antigen, both free and antibody bound, would w iden its use for confirming anti-HCV antibody positive patients and monitor ing a therapeutic response. This study has evaluated a prototype 'total' HC V core antigen immunoassay. Sera from 145 HCV negative blood donors gave a mean value of 54.9 (+/- 46.2) pg/ml based on recombinant antigen standards. Using these figures, the HCV core antigen cut-off was set as 200 pg/ml. Tw o hundred blood donors sera with indeterminant (a single-band on recombinan t immunoblot assay) HCV antibody statuses gave fully concordant HCV core an tigen results compared to their polymerase chain reactions (PCRs) - three p ositive, and 197 negative. HCV core antigen and PCR results were compared f or 59 sera from 19 HCV positive liver disease patients. The HCV core antige n results were in complete agreement with their PCRs for the nine patients always PCR positive and the three continuously negative. For six patients o n antiviral therapy whose qualitative PCRs changed from positive to negativ e, the HCV core antigen results paralleled the PCR results. The only discre pant results were from one patient whose PCR results went from negative to positive. 'Total' HCV core antigen testing will greatly improve the scope o f diagnostic tests for hepatitis C. (C) 2001 Elsevier Science B.V. All righ ts reserved.