Performance of parallel screening of Brazilian blood donors with two human immunodeficiency virus immunoassays: implications for sequential immunoassay testing algorithms in other countries

Abstract

Background In Brazil it is mandatory to screen donors for HIV antibodies using two immunoassays (IAs) in parallel. Confirmatory testing is performed only on reactive donors who return for counseling. The goal of this analysis was to determine if concordant IA reactivity accurately predicts infection and can be used for HIV incidence/prevalence analyses. Methods We reviewed HIV screening and confirmatory results obtained for 307,407 donations in the first year of the REDS-II study in Brazil (2007), and for 2,304,755 donations collected from 1996 to 2006 in one of the REDS-II sites (Sao Paulo). Results In the Sao Paulo site, 11,410 (0.50%) HIV-IA-reactive donations were discarded, but only 2,095 (0.09%) were reactive to both IAs. Western blot was positive on 1,002 (48%) dual-IA-reactive donors who returned for counseling. Only 4 HIV-infected donors were detected who had been missed at screening by one of the IAs; all occurred prior to 2002. The positive predictive value (PPVs) of dual-IA-reactivity varied from 45.8 to 100%, with 80–90% PPVs when using IAs from different manufacturers. If both assays yielded signal-to-cutoff (S/C) values ≥3.0, PPVs ranged from 91–99%, with ~99% sensitivity for true HIV seropositivity. Conclusion Parallel testing of all donations has limited efficacy when highly sensitive IAs are used. Reactivity by two sequential IAs is useful for prevalence studies if the assays are from different manufacturers and especially if high S/C values are considered.

Undisclosed human immunodeficiency virus risk factors identified through a computer‐based questionnaire program among blood donors in Brazil

“…Inclusion criteria were being an eligible blood donor at any of the four main aforementioned blood centers and having an HIV‐negative serostatus, as well as negative serologic status for Chagas disease, hepatitis B virus (HBV), hepatitis C virus (HCV), human T‐lymphotropic virus (HTLV)‐1/2, and syphilis. HIV was tested with two enzyme immunoassays (EIAs) using a dual strategy . Control donors for the HIV case‐control study were excluded from the study if they had indeterminate serologic results for any of the infections.…”

Human immunodeficiency virus prevalence, incidence, and residual risk of transmission by transfusions at Retrovirus Epidemiology Donor Study‐II blood centers in Brazil

“…Samples were considered confirmed seropositive if they were highly reactive by the LS‐EIA; if they were weakly or nonreactive by the LS‐EIA Western blot (WB) was performed as well as selective polymerase chain reaction testing. The sensitivity, specificity, and positive predictive value of this supplemental testing algorithm have recently been reported 15 …”

Number of recent sexual partners among blood donors in Brazil: associations with donor demographics, donation characteristics, and infectious disease markers

“…The kits used in each center were not necessarily the same. However, in the case of a reactive or borderline result for HCV, HTLV‐1/2, or HBsAg, testing was repeated at the Serology Division of FPS, with a second EIA kit that was not utilized by any of the three centers using previously reported procedures 9,10 . For each donation an overall positive marker result was defined as any one of the following scenarios: dual EIA‐reactive result for HBsAg, HCV, HTLV‐1/2, or HIV or a reactive result for syphilis or anti‐HBc screening.…”