Detection of hepatitis B virus DNA in blood units with anti-HBc as the only positive serological marker.

Serum samples from 10,629 blood donors were screened for hepatitis B virus (HBV) serological markers (HBsAg, anti-HBs, anti-HBc, anti-HBc IgM), anti-HCV, anti-HIV1/2 and ALT. Seventy five (0.7%) blood donors were found HBsAg-positive, 1,543 (14.5%) were carrying both anti-HBc and anti-HBs. whereas 507 (4.8%) samples were positive only for anti-HBc. Among the group of 507 anti-HBc positive samples, 303 were obtained from regular volunteer blood donors who were studied in two separate time intervals of at least 6 months' duration, and 204 were from first-time blood donors. The possibility of post-transfusion hepatitis B after donation of these 507 blood units was studied by determining the presence of HBV DNA as a marker of viral replication and infectivity. HBV DNA was detected by two methods (i) a chemiluminescent molecular hybridization assay, (ii) polymerase chain reaction (PCR) followed by DNA enzyme immunoassay (DEIA). Six out of 507 samples exhibited HBV DNA results in the gray zone of the hybridization assay, but were confirmed as negative by PCR DEIA. The other 501 samples were HBV DNA-negative by both methods, although 36 of them had increased ALT levels. No cases of post-transfusion hepatitis B were reported during the year in which these 501 blood units were provided. These results show that blood units which were positive only for anti-HBc, with normal ALT and were HBV DNA-negative may be considered not infectious for hepatitis B. Gray zone results of HBV DNA using hybridization quantitative assay must be confirmed as positive or negative by a more sensitive method such as PCR. Blood units which are anti-HBc-positive, with increased ALT levels and are HBV DNA-negative, which appear to not be related to HBV replication and infectivity, may be not safe for donation because of the potential existence of other as yet unknown, hepatotropic viruses.