To quantify adherence to oral therapies in ethnically diverse and economically disadvantaged patients with rheumatoid arthritis (RA), using electronic medication monitoring, and to evaluate the clinical consequences of low adherence.
A total of 107 patients with RA enrolled in a 2-year prospective cohort study agreed to have their oral RA drug therapy intake electronically monitored using the Medication Event Monitoring System. Adherence to disease-modifying antirheumatic drugs (DMARDs) and prednisone was determined as the percentage of days (or weeks for methotrexate) on which the patient took the correct dose as prescribed by the physician. Patient outcomes were assessed, including function measured by the modified Health Assessment Questionnaire, disease activity measured by the Disease Activity Score in 28 joints (DAS28), health-related quality of life, and radiographic damage measured using the modified Sharp/van der Heijde scoring method.
Adherence to the treatment regimen as determined by the percentage of correct doses was 64% for DMARDs and 70% for prednisone. Patients who had better mental health were statistically more likely to be adherent. Only 23 of the patients (21%) had an average adherence to DMARDs ≥80%. These patients showed significantly better mean DAS28 values across 2 years of followup than those who were less adherent (3.28 versus 4.09; P = 0.02). Radiographic scores were also worse in nonadherent patients at baseline and at 12 months.
Only one-fifth of RA patients had an overall adherence to DMARDs of at least 80%. Less than two-thirds of the prescribed DMARD doses were correctly taken. Adherent patients had lower disease activity across the 2 years of followup.