The hepatitis B virus (HBV) consists of an external envelope (HBsAg) and an inner core (HBcAg). The hepatitis core antigen comprises 183 – 185 amino acids.1 During an infection with HBV, antibodies to HBcAg (anti-HBc) are generally formed soon after the appearance of HBsAg, the initial antibody being mostly IgM class, which then declines in titer as levels of anti-HBc IgG start increasing.2 Anti-HBc (total) positivity persists in persons who have recovered from HBV infection and in those who progress to chronic HBV infection.3,4 Accordingly, they are an indicator of existing or past HBV infection.5 In rare cases, HBV infection can also run its course without the appearance of immunologically detectable anti-HBc (usually in immunosuppressed patients).7 Anti-HBc is not produced after vaccination.4,7
Due to the persistence of anti-HBc following HBV infection, screening for anti-HBc can be used to identify previously infected individuals.8 Determination of anti-HBc in association with other hepatitis B tests permits the diagnosis and monitoring of HBV infections.3,4 In the absence of other hepatitis B markers (HBsAg-negative persons), anti-HBc may be the only indication of an existing HBV infection.5,9