The relation between baseline HIV drug resistance and response to antiretroviral therapy: re-analysis of retrospective and prospective studies using a standardized data analysis plan

To assess the relation between resistance to antiretroviral drugs for treat ment of HIV-1 infection and virological response to therapy, results from 1 2 different studies were re-analysed according to a standard data analysis plan. These studies included nine clinical trials and three observational c ohorts. The primary end-point in our analyses was virological failure by we ek 24. Baseline factors that were investigated as predictors of virological failure were plasma HIV-1 RNA, the number and type of new antiretroviral d rugs in the regimen, and viral susceptibility to the drugs in the regimen, determined by genotyping or phenotyping methods. These analyses confirmed t he importance of both genotypic and phenotypic drug resistance as predictor s of virological failure, whether these factors were analysed separately or adjusted for other baseline confounding factors. In most of the re-analyse d studies, the odds of virological failure were reduced by about twofold fo r each additional drug in the regimen to which the patient's virus was sens itive by genotyping methods, and by about two- to threefold for each additi onal drug that was sensitive by phenotyping.