What is a rapid test for HIV-1 recent infection (RTRI)?
A test for HIV-1 recent infection (TRI) is a serological laboratory-based or point-of-care assay that classifies an HIV infection as recent or established, or long-term, infection. The period of recency will depend on the assay but is generally within 4 to 12 months. Recency tests are different from traditional rapid tests, i.e. they detect different antibodies or antibodies with different affinity, which is indicative of infection timing. Such laboratory-based assays generally produce a quantitative result, for which a cut-off that is set by the assay manufacturer is used to determine whether the infection is classified as recent or not.
CDC developed a new RTRI that can diagnose HIV infection and distinguish recent from long-term infection in a single lateral flow format. Absence or presence of a line is used to determine whether an individual has a recent infection or long-term infection, respectively. These tests are similar in concept to a HIV rapid diagnostic test but includes a third line that detects only long-term infection. Absence of this third line is indicative of recent infection. These tests can be performed in HTS, and results are available within 20 minutes. In contrast, laboratory-based test for recent infection (e.g. LAg-Avidity enzyme immunoassay [EIA]) are conducted in a central laboratory, require collection and transport of a blood specimen, and can take days to process and return results.