However, in real life in resource-limited settings, it may not be feasible to perform individual resistance testing. There have been a few reports on the pattern of HIV-1 drug resistance mutations in children who experienced failure of first-line NNRTI regimens from South Africa

[6], Uganda [7] and Thailand [8]. Data from an HIV-infected adult Thai cohort showed that the majority of patients who experienced failure of NNRTI regimens had M184V (89%), NNRTI resistance mutations (92%), thymidine analogue mutations (37%), GSK3235025 Q151M (8%) and K65R (6%). High plasma HIV RNA at the time of treatment failure was associated with a higher risk of multi-NRTI resistance [9]. There is a new NNRTI, etravirine, which, in contrast to nevirapine and efavirenz, requires multiple mutations to reduce drug susceptibility [10,11]. Therefore, it is important to assess the prevalence of etravirine-associated mutations in children who have experienced failure of first-line NNRTI treatment in order to predict the potential role of etravirine as a component of second-line regimens. The impact of mutations associated with etravirine has mainly been studied in the context of PI-based salvage regimens in adults

[12]. In the present study, we aimed to learn more describe the patterns of genotypic resistance mutations in children after failure of WHO-recommended initial NNRTI-based treatment regimens. The secondary objectives were to determine the prevalence and predictors of multidrug NRTI resistance and high-grade resistance to etravirine. The results of this study may be useful in making decisions regarding second-line antiretroviral drug regimens in children, especially in settings lacking access to individual genotypic resistance testing prior to

switching to a second-line regimen, and also in planning by policy makers of the provision of second-line regimens in their national programmes. We collected treatment outcome data from eight large paediatric HIV centres in Thailand for all children who experienced failure of NNRTI-based therapy and received a ritonavir-boosted PI regimen as second-line treatment. either Following Thai national AIDS programme, monitoring after initiation of ART included clinical response and CD4 monitoring every 6 months. Plasma HIV RNA measurement was performed only when treatment failure was suspected. Treatment failure was considered to have occurred when a child showed clinical disease progression, a suboptimal immunological response, defined as an increase in the CD4 percentage of <5% or an increase in the CD4 count of <50 cells/μL (age >5 years) over the first year of treatment, or immunological decline, defined as a decline in the CD4 percentage of >5% or a CD4 cell count drop of >30% from peak within 6 months. Genotypic resistance testing was recommended for plasma HIV RNA >1000 copies/mL, which has been provided free of charge under the national programme since 2005.