A simple and inexpensive particle agglutination test to distinguish recent from established HIV-1 infection

SummaryObjectivesWe sought to modify the Serodia HIV-1/HIV-2 particle agglutination assay (PA), a simple and cost-effective HIV assay that is used globally for the detection of HIV antibodies, as a sensitive/less sensitive test (S/LS) to identify recently infected individuals and to estimate HIV incidence.MethodsThe Serodia PA test was modified as an S/LS test (PA-LS) by using HIV antigen-coated gelatin particles at a dilution of 1:68 and a specific diluent, and calibrated using 37 HIV clade B seroconversion panels (309 samples) from Trinidad and from a commercial source that were tested at dilution intervals from 1:10 to 1:80 000. The greatest sensitivity for correctly classifying samples from recent and established infections was determined by receiver operator curve (ROC) analysis.ResultsAt a 1:40 000 sample dilution and a days post-seroconversion cutoff of 190 days, the PA-LS test yielded a 97% sensitivity for classifying recent and established infection samples. Furthermore, at a 1:20 000 dilution, the positive predictive value for correctly identifying recently infected individuals was 99%. The PA-LS test offers a 30–44-fold cost saving over currently available S/LS tests.ConclusionA modified, low cost and simple-to-perform PA test is appropriate for use in resource-limited countries, and has exhibited excellence in distinguishing recent from established HIV infection.