To evaluate adherence after treatment switch from a multiple-tablet regimen (MTR) to a single-tablet regimen (STR) in a national cohort of human immunodeficiency virus (HIV) patients.

This retrospective observational cohort, with data spanning January 1, 2000 to March 1, 2019, consisted of HIV infected patients receiving treatment from the Veterans Affairs (VA) health system. Patients were required to have a complete MTR regimen after January 1, 2006 and before December 31, 2018 with at least 60 days of treatment. Medical and pharmacy data were analyzed from the Veterans Affairs Informatics and Computing Infrastructure (VINCI) database. Statistical analyses examined differences in adherence when patients switched to a STR. Patients who switched to a STR were propensity score matched to those who never switched. Descriptive statistics and multivariable linear mixed effects models were utilized to evaluate differences in adherence between MTR and STR treatment in both the matched and unmatched samples.

A total of 5021 patients met the study criteria, 3906 patients in the MTR only cohort and 1115 patients in the switch to STR cohort. The unmatched cohorts were similar in terms of sex, index year, drug/alcohol abuse, and viral load but differed in terms of race, Charlson comorbidity and mental health conditions. The one to one propensity score matched cohort included 2230 patients, 1115 patients in each cohort. Among patients that switched from a MTR to STR, adherence increased on average from 65.9% to 78.12%. We find overall adherence is higher with STRs than with MTR HIV regimens in both the matched and unmatched sample and adherence declines with time for both STR and MTR regimens.

Switching to a STR is associated with higher adherence compared to MTR among patients with HIV treated with antiretrovirals. However, adherence declines over time with both STR and MTR regimens.