Reported adherence in rheumatoid arthritis (RA) varies widely (10.5-98.5%). Variability may result in part from different methods used to measure adherence. Our aims were to quantify adherence to antiarthritis medications for each method and to identify variability and associated factors.
The systematic literature review examined PubMed, the Cochrane central database, and article reference lists from 1970 to November 2014. Papers with medication adherence data (disease-modifying antirheumatic drugs, steroids, and nonsteroidal antiinflammatory drugs) in adult patients with RA or data on associated factors were included. Adherence rate was recorded for each method. Random-effect metaanalysis estimated adherence for different evaluation methods.
Adherence rate was 66% (95% CI 0.58-0.75). There were no differences in adherence among different measurement methods (interview, questionnaires, etc.). Regression analysis showed that adherence decreases during followup. Among 100 possible factors potentially effecting adherence, 7 adherence-associated factors were found in at least 2 different studies. These were the use of infliximab compared with etanercept or methotrexate (MTX), use of MTX compared to sulfasalazine or to etanercept, belief in the necessity of the medications, older age, and white race.
Overall adherence rate was 66%. We suggest that readers appraise adherence studies according to the medications evaluated, the validity of the method, and the scales and cutpoints.