Questionnaires on adherence to antihypertensive treatment: a systematic review of published questionnaires and their psychometric properties.

Background Non-adherence to antihypertensive treatment is currently considered one of the most significant risk factors in failure to achieve controlled blood pressure values. It is therefore extremely important to measure patient adherence to antihypertensive treatment. One way to measure adherence is through questionnaires. Numerous questionnaires for measuring adherence to antihypertensive treatment have been validated, but it not easy to choose one of them as being more appropriate than all of the others. Aim of the review The aim of this study was to identify and assess questionnaires designed to measure non-adherence to antihypertensive treatment, and to discuss their psychometric properties. Method A systematic review of the literature contained in PubMed and Scopus databases was undertaken to identify validated questionnaires on adherence to antihypertensive treatment up to October 2017. PRISMA guidelines were followed to conduct and report this review. Selection of articles and data extraction were performed by two independent researchers. When there was lack of agreement, a third researcher mediated in the discussion between the first two authors so that consensus could be reached. Results 39 articles were obtained containing 17 different questionnaires for measuring adherence to antihypertensive treatment. These questionnaires were validated in 15 countries. The number of items in the questionnaires ranged from three in QAM-Q to 33 in TAQPH. Hill-Bone compliance to high blood pressure therapy scale, Morisky-Green-Levine test and an 8-item Self-Reported Medication Adherence Measurement were the most widely validated questionnaires. Validity was analyzed more than reliability. Many of the questionnaires do not provide information on content validity. Construct validity and concurrent validity are analyzed in almost all of the questionnaires, and give highly variable results. By contrast, known-groups validity was not analyzed to any great degree. As regards reliability, almost all of the questionnaires provided Cronbach's alpha information with reasonably acceptable results, but temporal stability was not analyzed to any great degree. Conclusion None of the questionnaires included in the review demonstrates fulfilling all of the validity tests (content validity, construct validity and criterion-related validity) and reliability tests (homogeneity and temporal stability) in an acceptable manner. Therefore, none of them can be considered a Gold Standard.