Economic donor screening for anti-HIV in the developing world [letter]

Laboratory managers of poorly-funded transfusion laboratories in developing countries should consider screening donor sera in small pools with the newest generation of combined HIV-1/HIV-2 enzyme immunoassay (EIA) reagents. Pooling sera provides considerable cost savings with minimal loss of sensitivity in areas where she expected HIV prevalence among blood donors is less than 5%. It is most valuable in transfusion centers where the expected HIV prevalence is less than 1%. For example centers which test at least 100 donor sera at a time and have an expected HIV prevalence rate less than 1% can realize an at least 4-fold reduction in reagent costs. A study has shown that the Wellcozyme HIV-1+2 (VK55) EIA identified 35 of the known HIV-positive sera when 17688 specimens were screened in pools of 6. The same EIA in pools of 12 as well as IAF Biochem Behring and Diagnostic Pasteur EIAs also detected the 35 known HIV-positive sera. Thus pooling did not result in a loss in sensitivity. Researchers have found that EIAs used to screen specimens from plasmapheresis donors in the process of seroconversion correctly detected all seroconverters within a week. This indicates that screening in pools of 6 results in little to no delay in identifying newly HIV-infected donors. The Central Public Health Library in London retested 34 HIV-reactive specimens at a dilution of 1 in 6 in anti-HIV negative serum and found that just 8 remained reactive suggesting that pooling also increases specificity. Disadvantages of pooling include delay caused by individual testing of reactive pools a possible false negative reaction in the rare case of a coincidence of an antigenemic specimen and an HIV-positive specimen and the need for meticulously formed pools with carefully recorded components. These disadvantages point to the need for well-funded laboratories to avoid pooling.