HBSAG SUBTYPE DISTRIBUTION AMONG DIFFERENT POPULATIONS OF HBSAG-CARRIERS IN SPAIN

Data concerning the HBsAg subtype distribution in Spain are out-of-dat e and confined to a restricted geographical area. Furthermore, the com plex distribution observed in the countries surrounding Spain prevents any prediction. To obtain further data on HBsAg subtype distribution among Spanish HBsAg carriers, subtyping analysis (d and y determinants ) was performed in 670 samples from subjects belonging to various epid emiological risk groups and coming from different geographical areas o f the country. Similar frequencies were found for both mutually exclus ive d/y subtype determinants among non-risk, normal HBsAg carriers fro m almost all geographical areas studied. In contrast, the ay subtype w as clearly predominant (79-87%) among intravenous drug users, irrespec tive of their geographical origin. Thirteen different institutions for mentally retarded patients behaved as closed communities for HBV circ ulation, showing independent subtype distributions. Thus, no significa nt geographical variations were found for HBsAg subtype distribution i n Spain. The prevalence of each particular subtype is mainly dependent on the epidemiological characteristics of the carriers studied. Subty pe distribution was independent of the presence of HBeAg or HDV infect ion serum markers when homogeneous groups were considered separately. Atypical HBsAg phenotypes, either with coexistence or absence of both subtype determinants, were found in some cases.