Predictive validity of the 5-item Compliance Questionnaire for Rheumatology (CQR5) in detecting poor adherence of patients with rheumatoid arthritis to biological medication

Background: Adherence is a key factor for therapeutic success in patients with rheumatoid arthritis (RA). The aim of this study was to determine whether results from the 5-item Compliance Questionnaire for Rheumatology (CQR5) can predict future poor adherence to biological disease-modifying anti-rheumatic drugs (bDMARDs) in patients with RA, using medication possession ratio (MPR) as the gold standard comparator. Methods: RA patients starting a bDMARD were prospectively followed for 12 months. At baseline, CQR5 was collected in relation to the prescribed bDMARD. Patients were dichotomised into good adherers and poor adherers, categories that were then used as the variable in a predictive function analysis of the CQR5 in order to determine the accuracy of the classification at the end of the study period in comparison with the MPR. The sensitivity, specificity, and likelihood ratio of detecting poor adherers were also determined because this is the clinically important purpose of the questionnaire. Satisfactory adherence was defined as > 80% compliance with the prescribed dose regimen. Results: Of the 210 RA patients enrolled (147 women and 63 men; mean age 58.6 ± 12.8 years; mean disease duration 7.4 ± 2.5 years), at the end of the 12-month follow-up, 152 patients (72.4%) were good adherers and 58 (27.6%) were poor adherers according to MPR. Predictive analyses showed that the sensitivity and specificity of the CQR5 in detecting poor adherence were respectively 89.9% (95% CI 84.07-94.10%) and 80.8% (95% CI 67.46-90.37%). The accuracy of the CQR5 was 83.04% (95% CI 77.27-87.85%), the positive likelihood ratio (i.e. detecting ≤ 80% adherence) 4.67 (95% CI 2.58-8.18), and the area under curve 0.85 (95% CI 0.79-0.89). Conclusion: Higher baseline CQR5 scores significantly predict the treatment adherence of RA patients. This suggests that this instrument could be used for screening purposes in order to identify patients who are poorly adherent to bDMARDs.