“…In Brazil, it is mandatory to screen blood units by concomitant use of two approved enzyme immunoassays (EIAs) for HIV antibodies. To define prevalence, a sample was considered positive for HIV if reactive by both assays, based on our previous study, which showed that 85 percent of samples reactive by two EIAs test positive on Western blot (WB) 3 . During the study period, two of the following HIV kits were used in parallel: HIV‐1 and ‐2 antibody capture EIA (Ortho Diagnostic Systems, Raritan, NJ), an HIV‐1 and ‐2 antibody EIA enhanced with group O antigen (Vironostika HIV Uni‐Form II Plus O, Organon Teknika, Boxtel, the Netherlands), an HIV antigen and antibody combination assay (Murex, Dartford, UK), or an HIV‐1 EIA (Embrabio, São Paulo, Brazil).…”