Rapid HIV testing with same-day results: a field trial in Uganda

Abstract

Rapid, on-site HIV testing with same-day results may improve services and increase the number of clients who learn their serostatus in developing countries. To validate test performance under field conditions and assess the change in the proportion of clients who learn their serostatus, we conducted a field trial using the Capillus HIV-1/HIV-2 assay (Cambridge Diagnostics) at the AIDS Information Centre counselling and testing sites in Uganda. Compared to the standard 2-EIA testing algorithm, the sensitivity of Capillus was 99.6% (95% CI; 98.5%, 99.9%), the specificity was 98.8% (95% CI; 98.1%, 99.3%), the positive predictive value was 96.5% (95% CI; 94.5%, 97.8%), and the negative predictive value was 99.9% (95% CI; 99.5%, 100%). It took less than 5 min to perform a single test, and results were returned to clients in less than an hour, during which time clients were counselled. This resulted in a 27% increase in the proportion of clients who learned their serostatus and received counselling. We conclude that simple, rapid HIV tests can be performed accurately on-site within the time frame of a clinic visit, increasing the number of clients who learn their serostatus and receive post-test counselling.

PIP: The capability of rapid, on-site HIV testing with same-day results to improve HIV services in developing countries was evaluated through field studies conducted at AIDS Information Centers in Uganda. The screening test selected--Capillus HIV-1/HIV-2--is a direct latex agglutination assay performed on a plastic capillary agglutination slide. The rapid test protocol included anonymous registration, orientation and test decision counseling, phlebotomy, prevention counseling, and test result counseling. Clients received their result an average of 48 minutes after venipuncture, during which time they were counseled. When 2135 serum samples tested on-site in Kampala were compared with the standard 2-week enzyme immunoassay (EIA) testing algorithm used by the Nakasero Blood Bank, 520 samples were positive by both tests, 19 were Capillus-negative and EIA-positive, and 2 were Capillus-positive and EIA-negative. With an HIV prevalence of 24%, the negative predictive value of the Capillus test was 99.9% and the positive predictive value was 96.5%. The Capillus HIV test was associated with a 27% increase over the EIA in the proportion of clients who learned their serostatus and received counseling. Of concern, however, was the finding that only 16% of clients whose initial test was positive returned to the clinic for confirmatory results. Clients expressed a preference for same-day HIV results and, because of the reductions in time and expenses associated with a single visit, were willing to pay an average of US$3 for rapid testing. Overall, these findings suggest that rapid HIV testing is feasible under field conditions in developing countries with high HIV prevalence and can be completed within the time frame of a typical clinic visit.