Patterns of adherence with antiretroviral medications: An examination of between-medication differences

Objective: To determine whether adherence with one antiretroviral medicatio n reliably predicts adherence with other antiretroviral medications. Design: Cross-sectional repeated-measurement analysis. Setting: Cohort study enrolling patients from Massachusetts and Rhode Islan d. Patients: Total of 454 patients using antiretroviral medications for HIV in fection. Methods: For each antiretroviral medication, we asked patients to report ho w many days in the last week they had 1) missed a dose of the medication an d 2) been off schedule with a dose of the medication. The reliability coeff icient was used to compare between-person variance in adherence rates with total variance, which is the sum of between-person and within-person varian ce. Results: The mean age of patients was 42 years; 28% were women and 37% were nonwhite. Sixty-six percent of patients were on three or more antiretrovir al medications. Perfect adherence was reported by 42% of patients, and pati ents reported missing a dose on a mean of 1.5 days per week for each antire troviral medication currently being taken. The reliability coefficient for days in the last week that the medication was missed was 0.85 (95% confiden ce interval [Cl]: 0.83-0.87), and for days off-schedule in the last week, i t was 0.88 (CI: 0.86-0.89). Conclusions: Most of the variability in antiretroviral adherence in this st udy was accounted for by between-patient differences in overall adherence r ather than by within-patient differences in adherence patterns across medic ations. These data support the theory that when patients skip or are off sc hedule with doses, they skip or are off schedule with all the antiretrovira l medications taken at that time. In the course of exploring patients' adhe rence issues, clinicians may rind it useful to inquire about problematic do sing times. Researchers assessing adherence may not need to separately moni tor adherence with each antiretroviral medication in a regimen.