Incremental detection of HIV infections by the HIV Antigen/Antibody combination assays: An Australian experience

Detection of acute cases of human immunodeficiency virus (HIV) infection by the direct detection of HIV antigen or HIV nucleic acid assays is well known with an estimated 5-9 days reduction in the pre-seroconversion 'window period' by the detection of HIV specific antibodies. The aim of this study was to observe the impact following routine introduction of a screening assay which simultaneously detects HIV (type 1 & 2) antigen and antibody on the yield of acute HIV infection in multiple sites servicing different patient populations with a varying range of risk factors associated with HIV acquisition. During the first year (2003-2004), a total of 27 cases of acute HIV-1 infection were identified by the HIV-1/2 Ab/Ag combo test which were confirmed to be detectable for HIV antigen only that may have gone undetected should an HIV-1/2 antibody only assay have been used. Specimens referred from higher HIV case load centers were more likely to have provided relevant clinical information consistent with acute retroviral syndrome and relevant history of risk however there were numerous cases where no clinical information was provided. This study shows that routine introduction of HIV-1/2 antigen/antibody screening assays increases the identification of acute cases of HIV infection in low prevalence setting and may represent an important tool for enhanced surveillance of incident HIV infection and opportunities for prevention.