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To examine the consistency and comparability of anti-hepatitis B core antigen (anti-HBcAg) assays, four blood donation centers of the Red Cross in the Federal Republic of Germany tested 4,080 unselected blood donors with six different tests in parallel. Confirmation testing of reactive samples was done in the National Reference Center for Viral Hepatitis. Depending on the test kit used, 4.1 to 9.9% of serum samples were initially positive and 2.9 to 7.5% were repeatedly positive. Sixteen percent of serum samples were positive in at least one test but only three percent were positive in all six tests. Statistical analysis of frequency distribution of optical densities for each test suggested that there should be a correction of the cutoff values. This reduced the number of false-positive results by half, but a significant proportion of discrepant results could not be resolved. The lack of specificity and consistency requires cautious interpretation of isolated anti-HBcAg results in clinical specimens. Screening of predominantly anti-HBcAg-negative populations (e.g., blood donors) by the current anti-HBcAg test kits will almost necessarily give unsatisfactory results.

Within one year four butchers fell ill with acute hepatitis B in a butcher's shop with ten employees. A symptom-free hepatitis B virus carrier was detected among the non-diseased employees. Lack of IgM-anti-HBc antibodies showed that the carrier state had probably existed for more than one year. The time course of infections and the kind of cooperation made it very likely that the carrier had infected his symptomatic mates. The outbreak shows that hepatitis B can be an occupational disease also in non-medical occupations. Should hepatitis B occur in a workman exposed to trauma frequently due to his occupation, serological investigation of the workmates is required in order to identify potential sources of infection and to enable future protective measures.