Age, sex and transaminase dependency of specific and nonspecific results from enzyme immunoassays for antibodies to hepatitis C virus and follow-up of blood donors.

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.