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

Serum samples from 10629 blood donors were screened for hepatitis B virus ( HBV) serological markers (HBsAg, anti-HBs, anti-HBc, anti-HBc IgM), anti-HC V, anti-HIV1/2 and ALT. Seventy five (0.7%) blood donors were found HBsAg-p ositive, 1543 (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 ant i-HBc positive samples, 303 were obtained from regular volunteer blood dono rs who were studied in two separate time intervals of at least 6 months' du ration, 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 an d infectivity. HBV DNA was detected by two methods (i) a. chemiluminescent molecular hybridization assay, (ii) polymerase chain reaction (PCR) followe d by DNA enzyme immunoassay (DEIA). Six out of 507 samples exhibited HBV DN A results in the gray zone of the hybridization assay, but were confirmed a s 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-tr ansfusion hepatitis B were reported during the year in which these 501 bloo d units were provided. These results show that blood units which were posit ive only for anti-HBc, with normal ALT and were HBV DNA-negative may be con sidered 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-posi tive, with increased ALT levels and are HBV DNA-negative, which appear to n ot be related to HBV replication and infectivity, may be not safe for donat ion because of the potential existence of other as yet unknown, hepatotropi c viruses.