To validate the 19-item Compliance-Questionnaire-Rheumatology (CQR) against the "gold standard" in compliance measurement, electronic medication event monitoring.
Among 127 consenting patients, 81 with rheumatoid arthritis taking nonsteroidal antiinflammatory drugs (13 diclofenac, 20 naproxen) or disease modifying antirheumatic drugs (25 sulfasalazine, 23 methotrexate), 17 patients with polymyalgia rheumatica taking prednisone, and 29 patients with gout taking daily prophylactic colchicine (n = 12) or the uric acid lowering drugs allopurinol (10) or benzbromaron (7), 104 used their medication from a regular medication bottle fitted with a special cap containing microelectronics capable of recording time and date of opening and closing, defined as a medication event. Data were processed for the following: (1) the percentage of prescribed medication events during the study period (taking compliance) and (2) the percentage of days with the prescribed number of medication events (i.e., correct dosing). Satisfactory compliance was defined as taking compliance or correct dosing > 80%, while unsatisfactory compliance was defined as taking compliance or correct dosing < or = 80%. All patients were informed about the monitoring, and were followed for 6 months (gout: 1 year). At baseline 85 patients completed a set of questionnaires including the 19-item CQR.
A total of 85 patients who had complete questionnaire and electronic monitoring data were analyzed. Multiple linear regression analyses showed that the total, weighted CQR score significantly and adequately predicts taking compliance (p = 0.001, r2 = 0.46) and correct dosing (p = 0.004, r2 = 0.42). Discriminant analyses showed that specificity and sensitivity to detect good taking compliance were 95% and 62%, respectively, with a prevalence of good compliance of 52%. The predictive value to detect unsatisfactory taking compliance was 86%, and to detect good taking compliance was 83%. The likelihood ratio of the CQR-19 to detect low taking compliance was 11.6. Four items were especially predictive: fear of forgetting to take the drug, being able to function well, routines in daily life, and side effects (combined r2 = 0.35).
These results support the validity of the Compliance Questionnaire Rheumatology.