HIV antibody screening and confirmatory testing of Italian blood donors. One-year experience of a reference center.

During the first year (1986) of blood donor screening for antibody to HIV, 201,750 subjects were tested in 40 blood banks of Lombardia (Italy). All sera repeatedly positive by ELISA were submitted to our reference center for confirmation by Western blot (WB). Only 40 (0.02%) of 286 repeatedly reactive donors were positive by WB, whereas another 45 (0.022%) gave atypical antibody reactivities on WB, mainly directed against HIV core proteins. Of the 16 donors with inconclusive WB results followed for 4-12 months, 3 developed a full-blown antibody response, 5 maintained the anti-core reactivity throughout the follow-up period, and 8 lost all reactivities. The use of recombinant env and core antigen ELISAs seems to decrease the proportion of sera with inconclusive WB reactions, and to identify as true positive all seroconverting donors in advance of the WB test. The large majority (35 out of 40) of WB-positive donors and all seroconverters for antibody to HIV admitted to belong to a group at risk for AIDS. Among the 19 first-time donors with HIV infection, we found 3 subjects with serological evidence of LAV-2 infection. We describe also the diagnostic and ethical issues when a donor notification policy is based on WB confirmatory procedures.