Virological failure at one year in triple-class experienced patients switching to raltegravir-based regimens is not predicted by baseline factors

We evaluated rates and determinants of virological failure in triple-class experienced patients receiving raltegravirbased regimens from a national observational study over 48 weeks, defined by any one of the following: (1) no HIV-RNA suppression to undetectable levels (>50 copies/mL) during follow-up; (2) detectable viral load after obtaining undetectable levels; and (3) leaving the study before 48 weeks. Among 101 eligible patients, 26 (25.7%; 95% CI 17.2-34.2) had virological failure. No significant differences between patients with and without virological failure were observed for gender, age, route of transmission, baseline CD4/ HIV-RNA, CDC group, hepatitis B or C co-infections, resistance (based on the last genotype available), type and number of concomitant drug classes, concomitant use of darunavir, atazanavir, etravirine, enfuvirtide or maraviroc, and health-related qualityof- life measures. A high rate of treatment response was observed. The analyses did not identify any baseline factor associated with failure, including resistance status. Even if we cannot exclude the presence of pre-existing minority resistant variants not captured by genotypic tests, the lack of baseline predictors of failure suggests the need to monitor patients closely during follow up for other factors, such as potential drug interactions and reduced levels of adherence, which may favour virological failure.