Hepatitis B viral serum markers suggestive of infection by hepatitis B virus type 2 were found in 354 patients tested in the laboratory during a 2.5 year period of study. Confirmation of the HBsAg reactivity by neutralization and subtyping analysis and determination of serum HBV-DNA by molecular hybridization were carried out on selected samples from these patients. Clinical and epidemiological data were obtained from 234 patients and serological follow-up was done in 70 cases. The results obtained from the confirmatory tests and DNA assays indicated that HBsAg reactivities were specific, being frequently associated to low levels of HBV-DNA. The incidence rates obtained for HBV2 serological patterns among patients at different level of risk for HBV infection, as well as the finding of a high rate of coinfection with hepatitis A virus among those showing acute hepatitis, suggested that the HBV2 agent could be transmitted by the oral route. An hypothesis considering the so called HBV2 infections as resulting from infections by an HBV variant strain which has an improved ability for non-sexual, non-parenteral transmission is suggested. Specific recommendations for detection and confirmation of such cases in blood banks are also outlined.

An evaluation study, involving 11 screening methods for the detection of antibody to hepatitis C virus (anti-HCV) and a panel of 500 serum samples, was performed. Samples were tested by all 11 methods, and those showing reactivity in at least one method were studied by a combination of supplemental assays (recombinant immunoblot assays, first and second generation; neutralization test for anti-c100; synthetic peptide immunoblot assay; recombinant multi-dot immunoassay) and classified as positive (110 samples), indeterminate (4 samples), or negative (386 samples) on the basis of the results obtained. Second-generation recombinant methods performed better on positive samples than first-generation assays or synthetic peptide-based methods (99.1-100% correlation vs. 64.5-85.5% and 93.6-99.1%, respectively), whereas the latter showed higher correlations on negative samples than recombinant assays (97.4-99.7% vs. 82.4-93%). Further investigations, using broad panels of indeterminate samples from blood donors, should be done, however, before synthetic peptide-based methods are recommended for blood bank screening. Reactivity of samples must be confirmed by one supplemental test in all cases before the donor is informed. In some cases, it may require the use of two or more different tests to obtain definite conclusions.

Data concerning the HBsAg subtype distribution in Spain are out-of-date and confined to a restricted geographical area. Furthermore, the complex 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 epidemiological risk groups and coming from different geographical areas of the country. Similar frequencies were found for both mutually exclusive d/y subtype determinants among non-risk, normal HBsAg carriers from almost all geographical areas studied. In contrast, the ay subtype was clearly predominant (79-87%) among intravenous drug users, irrespective of their geographical origin. Thirteen different institutions for mentally retarded patients behaved as closed communities for HBV circulation, showing independent subtype distributions. Thus, no significant geographical variations were found for HBsAg subtype distribution in Spain. The prevalence of each particular subtype is mainly dependent on the epidemiological characteristics of the carriers studied. Subtype distribution was independent of the presence of HBeAg or HDV infection 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.

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