Differentiating recent from long-term HIV infections is possible thanks to the evaluation of HIV-specific immune response development or viral markers measurement. false recent rates among HIV clades and across populations. Application of these assays at an individual level is far more questionable because of person-to-person variability in the antibody response and the course of HIV infection, and because of the prospective regulatory approval requirements. In this article we review the principles and the limitations of the currently available major laboratory techniques that allow detection of recent HIV infection. The assays based on the alteration of serological parameters, as well Rabbit Polyclonal to GPRIN3 as the newest method based on an increase of HIV genetic diversity with the progress of infection, are described. non-recent infection, and in each infected individual the titer is generally rising gradually, at a similar rate during a period of several months after seroconversion. The assay procedure involves dual testing of the same sample with the same standard HIV diagnostic enzyme immunoassay. At first, a sensitive test is performed with a standard protocol, as recommended by the manufacturer. Secondly, samples confirmed to be anti-HIV-positive are submitted to the same immunoassay, but with the modified testing procedure, in order to make it less sensitive (detuned). The assay modification consists of increased sample dilution and reduced incubation times. Specimens that are anti-HIV-positive according to a sensitive test, and non-reactive (tested below the specified cut-off) on a less sensitive assay, are considered to be derived from recently HIV-infected persons. Individuals with long-standing infection and related high titer antibodies will remain reactive in the less sensitive version of the assay [15,16]. It should be remembered that the high sample dilution required in the detuned approach affects the accuracy of the assay results, and the highest precision here is essential. To reduce run-to-run variability of the detuned assay, the standardized optical density (SOD) is calculated CCB02 for each specimen with the CCB02 use of a calibrator . Initially, the detuned approach was developed for use with a first generation Abbott HIV-1 enzyme immunoassay (3A11 assay, Abbott Laboratories), which is currently not being produced. Another first generation immunoassay commonly used in a detuned approach was the Vironostika HIV-1 MicroElisa (bioMerieux, France) . Although the production of this assay had been ceased by bioMerieux, it is still available under a new name C the Avioq HIV-1 MicroElisa system (Avioq Inc., USA). The same commercial assay has been adapted for the detuned approach with the use of oral fluid, an alternative to the former serum-based testing strategies. Although it was shown that there is a good concordance between the oral fluid and serum-based sensitive/less CCB02 sensitive assay, further large-scale studies on the oral fluid test are necessary to develop a highly accurate assay with known mean RITA duration, which would offer significant advantages over serum-based methods . Newer, simpler rapid HIV diagnostic tests, such as the Determine HIV-1/2 assay (Abbott Laboratories, USA), OraQuick Advance HIV-1/2 assay (OraSure Technologies, Inc., USA) and CCB02 Uni-Gold Recombigen (Trinity Biotech, Ireland), as well as the HIV-1/2 particle agglutination test (Serodia, USA) have also been modified to render them less sensitive, and their ability to distinguish recent from long-term HIV infection has been tested [32C35]. Results were comparable to those obtained with the Vironostika HIV-1 MicroElisa detuned assay; nevertheless, additional investigation is still required to standardize rapid tests for the detection of recent HIV infection. After full calibration, validation and evaluation in cross-sectional settings, these tests could likely facilitate incidence estimations, as they do not require sophisticated laboratory instrumentation and infrastructure, and provide results in minutes. A common concern of the detuned assays based on modified commercial tests is their subtype B-dependent performance, which can limit their use in parts of the world in which other HIV clades predominate..