Evolution of HIV-1 transmitted drug resistance in Italy in the 2007–2014 period: A weighted analysis

Background: Recent studies suggest that transmitted drug resistance (TDR) may be decreasing in latest years, likely because of the reduced frequency of acquired resistance. However, specific risk factors, geographical areas and special HIV-infected populations may be disproportionally affected by TDR. Objectives: Correlates of TDR and time trends were evaluated from 2007 to 2014. Study design: We evaluated the genotypic results of 2155 naïve patients enrolled in the I.Co.N.A cohort at 23 clinical Centers in Italy between 2007 and 2014. A weighted analysis was performed to account for the patients enrolled in the cohort in each clinical Centre at each biennium (total number of patients: 3737). Results: Overall prevalence of TDR was 10.7%. Independent predictors of TDR were sexual risk factor (OR 2.315, p = 0.020) and non-Italian geographical origin (OR 1.57, p = 0.038). The weighted prevalence of TDR was 10.5% with a stable proportion over calendar years. Generally, TDR prevalence was numerically higher, although not significantly, in clinical Centers of metropolitan areas with more than 3 millions of residents as compared to others (11.3% vs. 9.2%). The difference in TDR prevalence between these Centers decreased in more recent years. Conclusions: A stable frequency of TDR was observed during the most recent years in Italy, with opposite and converging trends in large metropolitan areas as compared to the rest of the country, suggesting a more homogeneous spread of TDR across the country in latest years. Concerns remain for sexual route of infection and non-Italian origin, reinforcing the need for specific prevention strategies prioritizing specific populations.