Extent of human immunodeficiency virus type 1 drug resistance as a predictor of virological failure after genotype-guided treatment switch

Little is known about factors involved in virological response to treatment changes guided by genotyping in patients whose highly active antiretroviral therapy (HAART) fails. A 12-month observational study was conducted of 45 patients infected with human immunodeficiency virus (HIV)-1, who underwent a new genotype-guided HAART regimen following virological treatment failure. Logistic regression models were used to define factors predictive of virological response to genotype-assisted treatment switches. Virological response was defined as achievement of a level of plasma HIV-1 RNA <1000 copies/mL at the end of the follow-up. Drug-resistance mutations were detected at baseline in 30 patients (66.7%). A sustained virological response to new treatment occurred in 13 (43.3%) of these, as opposed to 11 (73.3%) of the 15 patients harboring drug-susceptible virus at baseline (P=.07). In multivariate logistic regression analysis, the number of drug classes where there was resistance at baseline was the only independent predictor of virological failure (P=.0313). Lack of virological response to genotype-guided treatment changes is primarily due to complex baseline resistance patterns. Benefits of antiretroviral resistance testing may be seriously limited by the lack of subsequent treatment options for heavily pretreated patients.