HCV serology: an unfinished agenda

Over 50 years have elapsed since the clinical definition of non-A, non-B hepatitis and 36 years since the unveiling of hepatitis C virus (HCV) and the availability of specific serological assays, but few advances in the serological diagnosis of HCV infection have occurred. Testing for anti-HCV is still based on the detection of reactivity towards the structural Core region of HCV, which appears to be dominant throughout the different phases of infection, plus antibodies towards antigens expressed by several non-structural regions. Unlike testing for other viral diseases, antibodies towards the envelope region are not detectable by the first line assays employed for screening or diagnosis and are scarcely represented in the supplementary assays employed to confirm the reactivity by screening assays. Clinical laboratories are often confronting issues on samples that give discrepant results among assays and are not confirmed by supplemental testing. Results obtained on those samples are usually labelled as 'indeterminate' and are often considered as false positive - though a true reference to define anti-HCV positivity is still lacking. The diagnostic answer is then deprived of clinical significance and affects patient management and counselling. The only advance, though not recent, has been the availability of assays detecting the HCV core antigen, which is considered as a surrogate of HCV RNA, with lesser sensitivity but bearing some operational and economic advantages in diagnosis and population screening, and lately of assays combining HCV antigen and anti-HCV detection. This paper summarizes the history of HCV serology and provides some insights on its limitations and potential developments.