Evaluation of an alternative confirmatory strategy for the diagnosis of HIV infection in Dar Es Salaam, Tanzania, based on simple rapid assays.

Alternative confirmatory strategies for detection of antibodies to HIV using enzyme-linked immunosorbent assays (ELISAs) have been shown to be useful in laboratories with limited resources. Three simple and rapid HIV antibody detection assays (Capillus, Serocard and Determine) were evaluated using 1412 fresh serum samples in order to formulate an alternative confirmatory strategy for the diagnosis of HIV infection. All sera were also tested by an anti-HIV ELISA and all sera reactive by any of the assays were tested by a second ELISA as well as by Western blot. Three hundred and eighty-three sera were found to be HIV-1 antibody positive, while 1017 sera were HIV antibody negative; 12 sera which were reactive by one or more of the simple assays had indeterminate Western blot results and these were considered HIV seronegative during the analysis. All assays had a sensitivity of 100%. The initial specificity of the assays were 98.7, 98.2 and 97.9% for Capillus, Serocard and Determine, respectively. In an alternative confirmatory strategy the use of Capillus followed by Serocard or Determine gave a specificity of 99.9 and 99.8%, respectively. Serocard followed by Determine gave a specificity of 99.3%. A testing strategy with 100% specificity (95% CI; 99.6-100%) could be achieved by the sequential use of all three simple/rapid assays or by repeat testing by Capillus followed by Serocard.