The Development of Tests for Recent Infection: From Detuned ELISAs to Recent Infection Testing Algorithms (RITAs)
Since 1995, when Brookmeyer and Quinn introduced the notion of estimating incidence from the prevalence of ‘recent’ infection (there indicated by the detection of p24 antigens in the absence of HIV antibodies), there has been much development in the area of tests for recent infection.
The timeline below (click the blocks to be directed to the relevant references) captures the key developments of tests for recent infection. In the earlier years, a test for recent infection made use of a less-sensitive or detuned version of an existing diagnostic assay measuring antibody titre, then referred to as a Sensitive and Less-Sensitive Assay (SALSA) or Serological Testing Algorithm for Recent HIV Seroconversion (STARHS). The BED assay, developed specifically for incidence estimation (with recent infection indicated by a low proportion of HIV-specific Immunofaceglobin G (IgG) in total IgG) has been used in numerous studies worldwide. Over more recent years, a number of new and novel approaches have been proposed (for example, based on antibody avidity, genome diversity, and combining a number of measured biomarkers and clinical indicators), and tests for recent infection are now referred to more generally as Recent Infection Testing Algorithms (RITAs). Developers continue to face the challenge of producing robust tests that have sufficiently large mean durations of recent infection and small false-recent rates.