A Combination of Poor Adherence and a Low Baseline Susceptibility Score is Highly Predictive for HAART Failure

The relationship between adherence, virological response to highly active antiretroviral therapy (HAART) and the presence and development of genotypic resistance was assessed in 41 HIV-infected patients on HAART. Four adherence parameters (drug taking adherence, dosing adherence, timing adherence and drug holidays) were scored prospectively using electronic event monitoring. Genotypic resistance at baseline and after therapy failure was scored retrospectively and a genotype-based susceptibility score was calculated. Overall median adherence rates were high. All adherence parameters were better in virological responders (n=31) compared to non-responders (n=10), drug taking adherence and number of drug holidays being significantly different. Responders had a significantly higher susceptibility score. Stepwise logistic regression showed that the number of drug holidays and a low susceptibility score were highly predictive for therapy failure. Despite the presence of a limited number of baseline resistance mutations, perfectly adherent patients can control virus replication for a prolonged period.