Testing is usually qualitative in these circumstances. Some studies have suggested that quantitative monitoring of the proviral DNA load may be informative in elite controllers (patients who show undetectable plasma HIV RNA in the absence of therapy) [1] and those patients who have undetectable plasma

HIV RNA on therapy [2-4]. PD0325901 ic50 To date, these applications are research tools only and evidence of their clinical utility remains limited. The prevalence of antiretroviral drug resistance among treatment-naïve patients in the UK is around 8% [1]. Although previous estimates may have been confounded by selection bias, prevalence rates have been declining over recent years [2]; however, rates are now showing a possible slight increase. While the highest rates of resistance are seen in patients born in the UK [3], rates are increasing in countries

currently expanding access to ART [4-6] and may soon start to rise among immigrant populations as a result [7]. In some cases, the presence of resistance in an apparently treatment-naïve patient may in fact reflect previous undisclosed therapy. There IWR-1 mw is increasing evidence to indicate that transmitted resistance negatively impacts on treatment responses, particularly in the context of nonnucleoside reverse transcriptase inhibitor (NNRTI)-based regimens [8-17]. Most transmitted drug resistance affects reverse transcriptase and protease inhibitors (PIs), although transmitted integrase inhibitor resistance has started to emerge. Although transmitted resistance often remains detectable in plasma for several years, gradual reversion to low-frequency and archived mutants occurs over time [18-24].

Reversion may occur through intermediates (or ‘revertants’, e.g. T215D/N/S from T215Y/F). Genotypic tests should therefore be used in treatment-naïve individuals as they allow the detection of such mutations that do not confer phenotypic resistance but may signal the presence of more substantial resistance. Detection of such revertants should be interpreted as an indication that fully resistant mutants are present as either low-frequency quasispecies or archived resistance. Both genotypic and phenotypic resistance assays provide results based Celecoxib on the majority population of circulating viruses at the time of sampling. The level of detection of mutant viruses is around 20–30% of the population in genotypic assays and probably less in phenotypic assays. Low-frequency mutants can impact negatively on responses to therapy in the context of NNRTI-based regimens (reviewed in [12, 15-17, 25, 26]). Assays with increased sensitivity for detection of resistance mutations are under development but can be considered primarily as research tools in most circumstances at the current time [16]. Testing for resistance is recommended in all newly diagnosed patients.