Development and validation of a multidimensional questionnaire assessing non-adherence to medicines

Abstract

The study aimed to develop and validate an instrument capable of measuring non-adherence to drug treatment in its multiple dimensions. The Questionário de Adesão a Medicamentos (Adherence to Medicines Questionnaire) with three questions was applied to 46 people with arterial hypertension in the city of Blumenau, Southern Brazil, in 2006. Non-adherence measures obtained were compared to four other methods (Haynes, Morisky, pill count and clinical outcome). Non-adherence measures varied according to the method. The combined Questionário de Adesão a Medicamentos non-adherence measure was 47.8% (95% CI: 32.9;63.1), whereas the gold standard was 69.6% (95% CI: 54.3;82.3). Accuracy measures to detect non-adherence showed a sensitivity of 62.5% and specificity of 85.7%, ROC curve area of 74.1%, and positive predictive value of 90.9%. Results suggest the Questionário de Adesão a Medicamentos has a good fit.