Detecting acute HIV infections is important because this infection contributes disproportionately to the transmission of HIV and highly contagious.
A study evaluating the performance of an HIV antigen/antibody (Ag/Ab) combination assay found the screen detected 82% of acute HIV infections detectable by pooled HIV RNA testing, resulting in a positive predictive value of 59%.
The finding is important because acute HIV infection, with its high viral load and similar viral variants, contributes disproportionately to the transmission of HIV and is highly contagious. Philip J. Peters, MD, of the CDC, and colleagues calculated that use of the HIV Ag/Ab combination assay increased the absolute HIV diagnostic yield by 0.15% (a 10.4% increase in the relative diagnostic yield). The study was published in JAMA.
People with acute HIV infection are often unaware they are infected, so identifying these individuals is critical to prevent further HIV transmission. Prior to this study’s publication, there had been a question as to what the best way is to detect acute HIV infection: assays that detect either HIV RNA or the p24 antigen, both of which are detectable early after HIV infection and before antibody response develops.
HIV Ag/Ab combination assays have a lower sensitivity compared with pooled HIV RNA testing, in which multiple HIV antibody-negative specimens are combined and tested together. But pooled HIV testing has not been used widely because only one RNA assay is FDA approved, and the pooling protocol is logistically complex and takes more time. Furthermore, the ability of pooled HIV testing to detect acute HIV infection had not been proven.
In the present study, researchers performed 86,867 HIV tests from September 2011 to October 2013 at centers in New York, New York; Winston-Salem and Raleigh-Durham, North Carolina; and San Francisco, California. Established HIV infection was diagnosed in 1158 individuals (1.33%) with few rapid HIV test results determined to be false-positive. The HIV Ag/Ab combination assay result was repeatedly reactive for all 1158 with established HIV infection and negative for all 19 rapid specimens with a false-positive result.
Acute HIV was diagnosed in 168 people (0.19%) by testing specimens that were negative by rapid HIV testing (n = 85,690) with HIV Ag/Ab combination and pooled HIV RNA assays. The Ag/Ab combination assay was reactive in 227 or these specimens, of which 134 were confirmed as acute HIV infection on individual HIV RNA testing, and 93 were determined to be false-positive test results.
“Because rapid HIV testing detected HIV infection in only 87.3% of HIV-infected participants, alternative strategies such as using a laboratory-based HIV Ag/Ab combination assay that can detect acute infection should be considered in high-prevalence populations in the United States,” the investigators concluded.