The sensitivity of an HIV P24 antigen and antibody assay used in paralel (3rd Generation) compared to HIV antigen/antibody combination assays (4th generation) to detect recent HIV infection in South African blood donors as identified through nucleic acid

Abstract: Introduction Although Nucleic Acid Testing has become the gold standard for the detection of HIV it remains an expensive technology. In Africa the use of sensitive serological assays might be a more viable option. HIV Combo assays have been on the market for several years and have been evaluated. Four cases of a 2nd diagnostic window period have been reported by the use of these assays. This raised questions regarding the sensitivity of these Combo assays compared to stand-alone serological assays for HIV detecting antigen and antibodies separately. In this study the sensitivity of three HIV Combo assays were compared to stand-alone assays by the use of 2 unique sample groups of early HIV infections as identified by NAT since 2005 by the South African National Blood Service (SANBS). Methods A retrospective study using two sample groups of archived plasma from HIV positive blood donors; A) 153 HIV NAT yield samples B) 87 low antibody ratio (Abbott Prism) recent HIV samples. These groups were tested by three HIV Combo assays (Abbott, Biorad and Roche) and one p24 antigen assay (Innogenetics). The Abbott Prism HIV O Plus assay results were already available as reference method for antibody detection. Sensitivity to detect HIV antigen and/or antibodies were evaluated. The significance of donor demographic indicators of donor group (new, re-joined or active) race, age, gender and region were analysed in relation to the presence/absence of p24 antigen between the two groups..