Adherence to protease inhibitor therapy and outcomes in patients with HIV infection

Background: Combination antiretroviral therapy with protease inhibitors has transformed HIV infection from a terminal condition into one that is manag eable. However, the complexity of regimens makes adherence to therapy diffi cult. Objective: To assess the effects of different levels of adherence to therap y on virologic, immunologic, and clinical outcome; to determine modifiable conditions associated with suboptimal adherence; and to determine how well clinicians predict patient adherence. Design: Prospective, observational study. Setting: HIV clinics in a Veterans Affairs medical center and a university medical center. Patients: 99 HIV-infected patients who were prescribed a protease inhibitor and who neither used a medication organizer nor received their medications in an observed setting (such as a jail or nursing home). Measurements: Adherence was measured by using a microelectronic monitoring system. The adherence rate was calculated as the number of doses taken divi ded by the number prescribed. Patients were followed for a median of 6 mont hs (range, 3 to 15 months). Results: During the study period, 45 397 doses of protease inhibitor were m onitored in 81 evaluable patients. Adherence was significantly associated w ith successful virologic: outcome (P < 0.001) and increase in CD4 lymphocyt e count (P = 0.006). Virologic failure was documented in 22% of patients wi th adherence of 95% or greater, 61% of those with 80% to 94.9% adherence, a nd 80% of those with less than 80% adherence. Patients with adherence of 95 % or greater had fewer days in the hospital (26 days per 1000 days of follo w-up) than those with less than 95% adherence (12.9 days per 1000 days of f ollow-up; P = 0.001). No opportunistic infections or deaths occurred in pat ients with 95% or greater adherence. Active psychiatric illness was an inde pendent risk factor for adherence less than 95% (P = 0.04), Physicians pred icted adherence incorrectly for 41% of patients, and clinic nurses predicte d it incorrectly for 30% of patients. Conclusions: Adherence to protease inhibitor therapy of 95% or greater opti mized virologic outcome for patients with HIV infection. Diagnosis and trea tment of psychiatric illness should be further investigated as a means to i mprove adherence to therapy.