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Performance of parallel screening of Brazilian blood donors with two HIV immunoassays: Implications for sequential immunoassay testing algorithms in other countries
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1 2011
Source: Transfusion. 51(1):175-183 -
Alternative Title:Transfusion
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Personal Author:
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Description: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.
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Pubmed ID:20633245
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Pubmed Central ID:PMC3019293
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