Discordant resistance interpretations in multi-treated HIV-1 patients.

The routine determination of drug resistance has become an important part of the clinical management of HIV-1 infected patients. Plasma samples from 130 individuals treated for at least 1 year with multiple NRTIs and NNRTIs were tested for the presence of mutations correlated to drug resistance. Since interpretation criteria represent a crucial point for virologists and clinicians, often complicated by the presence of novel and/or complex mutations patterns, we analyzed results interpreted by TruGene HIV-1 (Visible Genetics, Toronto, Ontario, Canada) and VirtualPhenotype (Virco, Mechelen, Belgium). A high degree of concordance was found for NNRTIs whereas NRTIs interpretation was highly discrepant. Since different approaches to monitoring resistance reflect different interpretation of results, the prediction of drugs resistance from a given HIV sequence might be contradictory and requires accurate standardization and unique interpretative rules.