The association between HIV drug resistance testing, viral suppression and mortality in Ontario: a retrospective...

Drug resistance compromises the effectiveness of antiretroviral therapy (ART). Resistance testing prior to initiating therapy is recommended in guidelines in many high-income countries, and it has been shown to improve outcomes after first-line ART regimen failure. There is limited evidence on its role in treatment-naïve individuals. We sought to investigate the association between resistance testing and viral suppression and mortality in people living with HIV initiating treatment in Ontario, Canada, where resistance testing became standard of care in 2014.

We conducted a retrospective cohort study from 2005 to 2018 using Ontario health administrative databases linked to the Ontario HIV Treatment Network (OHTN) Cohort Study (OCS). Eligible cohort participants were those who had complete data within the follow-up time range. We used logistic regression to compare the odds of viral suppression (<200 copies/mL, at 6-18 months) and death between people living with HIV who had a record of resistance testing prior to treatment and those who did not. We adjusted for age, sex, year ART was started, race, sexual orientation, level of education, income, adherence, anchor drug, immigration status, injection drug use, viral load and baseline CD4 count.

Of 1806 eligible participants, 716 were analysed for death, of which 3.7% had died at the end of follow-up. Six hundred and ninety-nine (699) were analysed for viral suppression, of which 94.6% achieved viral suppression. Resistance testing prior to ART initiation had no significant association with viral suppression (odds ratio [OR] 1.13; 95% confidence interval [CI] 0.58-2.22) or death (OR 1.06 95% CI 0.49-2.28) in the covariate-adjusted models. Viral suppression was more likely in older age and in people who started treatment with non-nucleoside reverse transcriptase inhibitors compared to protease inhibitors, and in people with a higher baseline CD4 count. The odds of death were higher in individuals who were older.

Resistance testing was not associated with viral suppression and death. Outcomes were associated with clinical and demographic factors, notably regimen, baseline CD4 count and age.