HIV Drug Resistance among Pre-treatment Cases in Thailand: Four Rounds of Surveys during 2006-2013.

In Thailand, antiretroviral therapy (ART) was initiated to treat human immunodeficiency virus infection and acquired immune deficiency syndrome (HIV/AIDS) cases using the empirical regimen with no prior genotypic test to determine drug resistance. In order to assess prevalence rate of HIV drug resistance (HIVDR) among pre-treatment cases, four rounds of survey were carried out in ART clinics, including six, eight, 33 and four ART clinics in each round during 2006-2013. For which, HIVDR testing results were available in 310, 350, 797, and 413 cases in four rounds. It was revealed that HIVDR rates among naive cases were 2.0%, 2.8%, 4.0% and 4.8%, while in experienced cases, the rates were 0, 3.3%, 11.4% and 13.9%. The rates among all cases were 1.9%, 2.9%, 4.4% and 5.6%. Resistant drugs with the highest rates among all cases in the survey round 4 were nevirapine (3.6%) and efavirenz (3.1%). The results indicated the need to continue surveillance for pre-treatment HIVDR, and posed challenges to implement activities for protecting efficacy and prolong the use of empirical first-line regimen. A strategy to apply genotyping test, in a cost-effective approach, should be considered to prepare for situation when HIVDR increases beyond a critical level.