Study ObjectiveTo evaluate the odds of achieving viral suppression in human immunodeficiency virus (HIV) patients using antiretroviral therapy as a single-tablet regimen (STR) or multiple-tablet regimen (MTR). DesignRetrospective cohort study. Data SourcesSouth Carolina Medicaid medical and pharmacy paid claims data were obtained from the South Carolina Revenue and Fiscal Affairs Office; laboratory data were obtained from the South Carolina Department of Health and Environmental Control. PatientsA total of 1536 patients who were dispensed a complete STR (477 patients) or MTR (1059 patients) regimen lasting at least 60 days between January 1, 2006, and December 31, 2013. Measurements and Main ResultsThe analysis examined adherence levels and regimen type on odds of viral load suppression. Regimen adherence levels (90-94%, 85-89%, 80-84%, and less than 80%) were compared with the gold standard adherence for HIV of 95% or greater. Patients were followed from index date until the earliest date of regimen discontinuation, treatment switch, end of study period, last date of eligibility, or death. Differences in outcomes were evaluated by (2), Wilcoxon rank sum statistical tests, and multivariate regression models controlling for covariates. For STR regimens we find that, when compared with 95% or greater adherence, there is no statistical difference in the odds of viral suppression with adherence levels greater than or equal to 80%. However, adherence levels greater than or equal to 95% were associated with a greater odds of viral suppression when compared with less than 80% STR adherence (odds ratio [OR] 2.57, Dunnett 95% confidence interval [CI] 1.04-6.32). For MTR regimens, there was no statistical difference in the odds of viral suppression for the adherence level 90-94% compared with the 95% or greater adherence (OR 3.59, Dunnett 95% CI 0.805-16.043). However, the 95% or greater adherence has greater odds of viral suppression compared with all other MTR adherence levels. In addition, no difference was found in the odds of viral suppression between STR and MTR for all adherence levels. ConclusionsCompared with 95% or greater adherence, STR regimens achieve viral suppression with adherence levels of 80% or greater, whereas MTR regimens require adherence levels of 90% or greater to achieve viral suppression in South Carolina Medicaid patients with HIV/AIDS.