Significance of Isolated Hepatitis B Core Antibody in Blood Donors

Background: About 25% of blood donors who test positive for antibody to hepatitis B core antigen (anti-HBc) have no other positive hepatitis B serologic results. Because of the potential importance and diagnostic uncertainty of this test result, we studied its significance by assessing the serologic response to hepatitis B vaccine in donors with an isolated anti-HBc pattern. Methods: Specimens from 300 blood donors that were positive for anti-HBc by enzyme immunoassay were tested for anti-HBc by radioimmunoassay and for antibody to hepatitis B surface antigen (anti-HBs). A subgroup of 37 were further studied after administration of hepatitis B vaccine and compared with 34 similarly vaccinated ageand sex-matched seronegative controls. Measurements of anti-HBs were made at vaccination and 1, 2, 4, 8, 25, and 30 weeks after initial vaccination. Results: Among 300 donors who tested positive for anti-HBc by enzyme immunoassay, the radioimmunoassay for anti-HBc was negative in 76 (25.3%) and the test for anti-HBs was negative in 104 (34.7%). Significant differences were observed for radioimmunoassay anti-HBc and antiHBs titers, alanine aminotransferase, and male-female ratios between four distinct serogroups (A through D) defined by the combination (positive/negative) of radioimmunoassay anti-HBc and anti-HBs results. No significant differences between the study and control groups were observed in the magnitude of anti-HBs responses at any of the six postvaccine testing periods. Conclusions: Isolated anti-HBc in US blood donors is usually a false-positive result, regardless of the titer.