A five item Compliance Questionnaire for Rheumatology (CQR5) can effectively predict low adherence to DMARDs in Rheumatology clinics
ABSTRACT Background: Polypharmacy, among other factors, has lead to high levels of non-adherence to DMARDs (30-50%), which impacts on successful treatment. The Compliance Questionnaire for Rheumatology (CQR19; de Klerk et al 2003) is a 19 item self report measure of medication adherence developed specifically for Rheumatic diseases. Previously, we have found that reducing the CQR19 to 5 items (CQR5) improves the reliability of the scale by removing extraneous items. The clinical application of the CQR is to detect low levels of medication adherence and when the original authors evaluated the predictive ability of the CQR19 against electronic medication monitoring, they found that the CQR19 was excellent at classifying patients. This study aims to determine the predictive value of the CQR5 at detecting <80% adherence to DMARDs.
Methods: The CQR19 was completed by 234 patients with an inflammatory arthropathy requiring DMARDs that were recruited consecutively from two UK Rheumatology clinics. Using the prediction equation given by the original authors, these patients were classified as “high” (>80%) or “low” (<80%) adherers based on their CQR19 responses. A discriminant function analysis was then carried out with the CQR5, to determine whether it could correctly classify patients. The sensitivity to detect low adherers was examined.
Results: The canonical linear discriminant analysis was highly significant (p<.001), indicating that the CQR5 effectively discriminated between high and low adherers. It correctly predicted membership of 88.5% of all cases. Of the two groups, 97% of high adherers and 68.6% of low adherers were correctly classified; however, more low than high adherers were misclassified (31.4% vs 3% respectively). The sensitivity and specificity (Table 1) also indicate that the CQR5 is excellent for detecting high adherers and very good for detecting low adherers.
Conclusions: The CQR5 is excellent at detecting high, and very effective at detecting low adherers, with 69% sensitivity. This is a high predictive rate for a very short, self report questionnaire that has the potential to alert clinicians to patients that are taking <80% of prescribed DMARDs. The questions could also indicate the reasons for non-adherence. The CQR5 is very quick and easy for patients to use and has a 91% positive predictive value for low adherers and therefore has excellent clinical utility.