Low prevalence of transmitted antiretroviral drug resistance in a large UK HIV-1 cohort.

OBJECTIVES To describe current practice in testing for transmitted antiretroviral drug resistance (TDR) and the prevalence of TDR in a large UK HIV-1 cohort. METHODS The study includes a retrospective analysis of newly diagnosed HIV-1-infected patients presenting to eight HIV clinics in the north of England between March 2005 and March 2007. Resistance mutations were defined by IAS-USA. Predicted phenotypes were calculated by the Stanford University database. RESULTS Five hundred and fifty-eight patients were studied, of whom 394 (70.6%) had heterosexually acquired HIV and 377 (67.6%) were infected outside the UK. TDR testing was performed in 406 patients (72.8%). Thirteen of 392 viral resistance profiles (3.3%) showed genotypic TDR. There was no significant association between TDR and any demographic or risk factor or baseline CD4 count. In particular, rates of TDR were similar in white British (6/147, 4.1%) and black African (7/224, 3.1%) patients. The numbers of patients with TDR to individual drug classes were: nucleoside reverse transcriptase inhibitors, 2 (0.5%); non-nucleoside reverse transcriptase inhibitors, 7 (1.8%); and protease inhibitors, 4 (1.0%). No patients had multi-class resistance detected. Eleven patients (2.8%) were predicted to have significant phenotypic resistance to at least one drug. CONCLUSIONS In a large unselected UK cohort, with high coverage of TDR testing, the prevalence of TDR was low and is in accordance with recent data, showing a decrease in the prevalence of TDR in the UK. Differences in population mix did not appear to explain this low rate.