Evaluation of HIV-1 drug resistance in newly diagnosed individuals in Italy over the period 2017-2023

Objectives We evaluated the prevalence of HIV-1 drug resistance in newly diagnosed individuals from 2017 to 2023, in Italy. Methods Transmitted drug-resistance (TDR) was evaluated by using the HIVdb algorithm (https://hivdb.stanford.edu/ ), through two different approaches: i) by considering the complete list of mutations included for the genotypic susceptibility score; ii) by considering only major resistance mutations. Logistic regression analysis was used to estimate association of TDR with calendar year. Results We analyzed 1,188 drug-naive individuals diagnosed in Italy between 2017 and 2023 enrolled in the Antiviral Response Cohort Analysis (ARCA) database. Most of them (∼75%) were males; their median (IQR) age was 40 (30-50) years. Non-B subtypes were found in 43.9% of participants and significantly increased over time (from 44.2% in 2017 to 54.8% in 2023, p=0.008). TDR prevalence was 29%, driven by NNRTI resistance (19.4%). Rates of NRTI, PI, and INSTI resistance were 4.7%, 4.4%, and 5.1%, respectively, with no significant temporal trends. When only major resistance mutations were considered, TDR prevalence was definitively lower (15.8%), primarily driven by NNRTI mutations (11.8%). Rates of major NRTI, PI, and INSTI resistance were 4.6%, 1.7% and 0.7%, respectively. Resistance to ≥2 drug classes was rare (1.9%). No association of major TDR with calendar year was found, except for 2023 (aOR: 2.33 [1.14-4.74], p=0.019). Conclusion Over the period 2017-2023, HIV-1 TDR appeared generally stable in Italy. However, the increased prevalence of major TDR in 2023 confirms the importance of a continuous TDR surveillance in newly diagnosed individuals to inform clinical practice.