Isolated antibody to hepatitis B core antigen in human immunodeficiency virus type-1-infected individuals.

We screened 651 human immunodeficiency virus (HIV)-1-infected subjects for hepatitis B surface antigen (HBsAg) and antibody to hepatitis B surface antigen (anti-HBs). Of a total of 387 subjects who tested negative for both HBsAg and anti-HBs, 142 underwent further testing for isolated presence of antibody to hepatitis B core antigen (anti-HBc). Of these 142 subjects, 60 (42%) tested positive for anti-HBc (isolated anti-HBc). Individuals coinfected with HIV-1 and hepatitis C virus (HCV) were more likely to have isolated anti-HBc than were subjects with HIV-1 alone (80% vs. 16%, respectively). Our findings suggest that individuals with HIV-1/HCV coinfection for whom there is no serological evidence for hepatitis B virus when screened with HBsAg and anti-HBs will be positive for anti-HBc in >75% of cases. A screening strategy that tests only for HBsAg and anti-HBs in HIV-1-infected patients will miss a large number of individuals with isolated anti-HBc.