The invention relates to a method of detecting HCV infection in a biological sample, the method comprising providing an immunoassay solid support, comprising an HCV anti-core antibody, an antigen comprising an HCV NS3/4a epitope, and an HCV multiple epitope fusion antigen, that can detect both HCV antigens and antibodies present in a sample. The invention also includes polynucleotides encoding multiple epitope fusion antigens for use in the assay, recombinant vectors and host cells comprising such polynucleotides, and methods of producing the multiple epitope fusion antigens.