Predictors of self-reported adherence and plasma HIV concentrations in patients on multidrug antiretroviral regimens

Background: Adherence to prescribed medications is a central feature of goo d clinical HIV care, but little is known about the factors associated with multidrug antiretroviral adherence, or about how such adherence is related to plasma HIV suppression. Methods: We collected data from 133 HIV-infected adults receiving antiretro viral therapy. Study subjects completed customized adherence self-report in struments and provided blood samples to measure plasma HIV-I RNA concentrat ions and CD4(+) lymphocyte counts. Regression models were used to determine the independent predictors of antiretroviral adherence and plasma HIV conc entration, and the relationships between the two. Results: Adherence was poor (average, <80% antiretrovirals/day) in 28% (95% confidence interval [CI], 20%-36%), fair (80%-99% per day) in 23% (95% CT, 15%-30%), and excellent (100% per day) in 50% (95% CI, 41%-58%) of study s ubjects. Mean decreases in HIV-1 concentration from highest-ever levels wer e 1.3, 1.6, and 2.0 log(10) copies/ml in these three groups, respectively ( chi(2); P < .02) Two-stage least squares regression demonstrated a -1.3 log difference in viral load associated with each category improvement in adhe rence. In multivariate models, confidence in medication-taking ability, or perceived self-efficacy, and convenience of the medication regimen, or "fit " with routine and daily activities, were also associated with greater medi cation adherence (odds ratios [OR] 5.3; 95% CT, 2.4-11.8, and 9.0; 95% CI, 1.8-45.3, respectively). The latter was also independently associated with a lower plasma HIV concentration (p < .02). Conclusions: Nonadherence to combination antiretroviral medications is comm on and is associated with increased levels of plasma HIV. Programs and clin ical efforts to improve medication taking should strive to integrate medica tions better into patients' daily routines and to improve patients' confide nce in their ability to take medications correctly.