Drug resistance testing at regimen failure in individuals diagnosed with HIV-1 between 2010 and 2018 in Israel

Objective:Assess virological failures, analyze the results of resistance testing (RET), and investigate factors associated with acquired drug resistance mutations (aDRM).Design:A retrospective longitudinal cohort study.Methods:Virological failures (viral load >50 copies/ml) from a cohort of 1130 individuals, diagnosed with HIV-1 in 2010-2018 and followed up until 2020, were included. Demographic, clinical, and virological data were collected. A piecewise exponential additive mixed model was employed to estimate the association of various factors with aDRM.Results:Only 82 individuals had virological failure, 20/82 had multiple virological failures. The majority of virological failures (77%) were men, 48% were Israeli-born,79% were diagnosed in 2010-2014. Only 18% initiated with second-generation integrase-inhibitor (INI) based regimens. Although no baseline differences were identified between those with single and multiple virological failures, the latter had lower CD4⁺ levels before first virological failure. NRTI M184IV and INI N155H were identified in more than 10% of the cases. In those with additional failures, INI N155H was more prominent in cases with subtype B compared to those with non-B subtypes (P = 0.039). Diagnoses with CD4⁺ cell count less than 200 cells/μl and AIDS [hazard ratio = 3.46, 95% confidence interval (95% CI): 1.51-7.92, P = 0.003], second-generation INI at the first virological failure (HR = 0.32, 95% CI: 0.11-0.91, P = 0.033), and RET at baseline (hazard ratio = 0.34, 95% CI: 0.13-0.86, P = 0.022) had a significant and persistent relative effect on aDRM.Conclusion:The risk for aDRM is reduced in those who are treated with second-generation INI-based regimens. Diagnosis with low CD4⁺ cell counts and AIDS is associated with detection of aDRM.