The prevalence of hepatitis-B antigen (HB S Ag) and its antibody (Anti-HB S) among London hemophiliacs and blood donors from London and two tropical areas.

The prevalence of hepatitis-B antigen (HB s AG) and its antibody (anti-HBs) among 49 London hemophiliacs was compared with that among women attending an antenatal clinic and healthy blood donors from London and from two parts of the tropics (Mauritius and Zambia). The prevalence of HBsAG and anti-HBs was low in antenatal patients, London blood donors and blood donors from Mauritius. However, a high proportion of hemophiliacs (59%) were anti-HBs positive, this being comparable with Zambian blood donors (53%), although anti-HBs titers in hemophiliacs were much higher (GMT 1:342) than in Zambian blood donors (GMT 1:36). In contrast, HBsAG was detected in 29 of 250 (12%) Zambian donors but in only 3 of 49 (6%) hemophiliacs. Clinically overt hepatitis occurred in only two hemophiliacs. However, the presence of HBsAG-specific IgM in 7 of 29 (24%) anti-HBs-positive hemophiliacs suggests that a proportion of these patients recently experienced subclinical infection by hepatitis-B virus, Anti-HBs-positive hemophiliacs received a significantly higher number of- cryoprecipitate units than did those without anti-HBs(P less than 0.01). Five of seven hemophiliacs with high titers of anti-HBs (greater than 1:4,096) showed a decline in titer after 1972 which may have been associated with the introduction of screening of cryoprecipitate for HBsAG.