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Background: Second-generation enzyme immunoassays (EIA-2) for antibodies to hepatitis C virus (anti-HCV) have an improved specificity and sensitivity compared to first-generation enzyme immunoassays (EIA-1). Therefore the question arises how many anti-HCV-positive blood donors were missed by the EIA-1, how many were false positive, how false-positive donors should be dealt with and how the results of the EIA-2 correlate with demographic data and surrogate testing for serum alanine aminotransferase (ALT). Material and Methods: A total of 208,544 individual North German blood donors not preselected for anti-HCV negativity were tested for anti-HCV with EIA-2 and, if repeatedly reactive (rr), with a licensed supplementary test (RIBA-2). Results: Overall, 0.43% of the donors were EIA-2 rr, but only 0.12% of women and 0.09% of men were RIBA-2 positive. RIBA-2 positivity rates were very low in donors 18 to 27 years old (0.03% and 0.05%) and clearly rose with age in women but not in men. The rate of unspecifically positive EIA-2 results (entirely negative in RIBA-2) rose with age in both sexes and did not correlate with ALT. The ALT distribution was age dependent with a completely different pattern for men and women. Anti-HCV positivity was strongly correlated with ALT albeit on a very low level: more than 97% of donors with strongly elevated ALT were anti-HCV negative. Follow-up and comparison of EIA-1, EIA-2 and RIBA-2 results for the subsequent donations showed that only 8% of now RIBA-2-positive donors were not detected by EIA-1. Apparent seroconversions in EIA-2 are usually not specific: only one out of 66 apparent seroconversions could be confirmed by RIBA-2. 0.15% of the donor population showed an inconsistent EIA-2 pattern during follow-up. Conclusions: We therefore suggest that donors should not be excluded from further donations on the basis even of multiple EIA-1 positive results or on the basis of only one EIA-2-positive donation. The value of ALT screening for transfusion safety should be reconsidered.

Anti-HIV test results of the Red Cross Blood Transfusion Service of Lower Saxony from 1 June 1985 to 31 July 1986 inclusive were analysed retrospectively. Nine out of 70,936 donors who had not donated blood before 1 June 1985 (first-time donors) and 9 out of 261,231 donors who had donated blood before this date (repeating donors) were found anti-HIV confirmed positive at the time of the first blood donation during the study period. The prevalence of HIV antibody in first-time donors was significantly higher than in repeating donors (p less than 0.01). It was concluded that some members of risk groups used blood donation to obtain an anti-HIV test result. One out of 30,300 blood donations was confirmed anti-HIV positive. The results of this study justify the transfusion of blood donations that are reactive only in the initial ELISA test.

Second generation enzyme immunoassays (EIA-2) for antibodies to hepatitis C virus (anti-HCV) have a higher specificity and sensitivity than first generation enzyme immunoassays (EIA-1). We studied how many anti-HCV-positive blood donors were missed by the EIA-1, how many were false positive, how false-positive donors should be dealt with and how the results of the EIA-2 correlate to demographic data and serum alanine aminotransferase (ALT) level. A total of 208, 544 northern German blood donors, not preselected for anti-HCV negativity, were tested for anti-HCV with EIA-2 and, if repeatability reactive (rr), were retested with a licensed supplementary test (RIBA-2). 0.43% of the donors were EIA-2 rr, but only 0.12% of women and 0.09% of men were RIBA-2 positive. RIBA-2 positivity rates were very low in donors 18 to 27 years old (0.03% and 0.05%) and rose with age in women but not in men. Infected women were significantly more often Rhesus-negative than men. The rate of unspecifically positive EIA-2 results (entirely negative in RIBA-2) increased with age in both sexes and did not correlate with ALT. The ALT distribution was age-dependent with a different pattern for men and women. Confirmation of EIA-2 results with RIBA was rare when ALT was low and frequent when ALT was high. ALT screening before introduction of Anti-HCV detected one out of six infected donors. To exclude this one infectious donation, 46 uninfected donations had to be excluded in addition. Only 8% of the then RIBA-2-positive donors were not detected by EIA-1. Apparent seroconversions in EIA-2 are usually not specific; only 1 out of 66 apparent seroconversions could be confirmed by RIBA-2 suggesting recent HCV infection. 0.15% of the donor population showed an inconsistent EIA-2 pattern during follow-up. We conclude that donors should not be excluded from further donations, even on the basis of multiple EIA-1 positive results or on the basis of only one EIA-2 positive donation. Anti-D-immunoglobulin prophylaxis may have been a source of infection in some Rhesus-negative women. ALT screening should not be discontinued because recent HCV infection can be detected earlier by ALT than by anti-HCV, but exclusion limits should be elevated to increase specificity and limit unnecessary exclusion of donations.

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