Abstract
BACKGROUND: Poor medication adherence in chronic illnesses such as Parkinson's disease (PD) is a significant but potentially addressable issue if core components are systematically measured. OBJECTIVE: To assess whether rating scales used in PD adequately cover essential components of medication adherence. METHODS: We accessed 5 databases targeting articles published before October 2019 and using rating scales to measure medication adherence in PD. The ABC Taxonomy from the European Ascertaining Barriers to Compliance Consortium and World Health Organization recommendations were used as the evaluation standard of 5 essential adherence dimensions (patient-based, health system-based, social-based, therapy-based, and health condition-based), 3 phases (initiation, implementation, and discontinuation), and 2 factors (intentional and nonintentional). RESULTS: We screened 192 and selected 16 studies, collectively using 5 medication adherence rating scales. No scale covered all essential components of medication adherence (dimensions, phases, factors). The Morisky Medication Adherence Scales were the most frequently used (11 studies), but they measure only 2 dimensions and phases. The Stendal Adherence to Medication Score (used in 1 study) measured all phases but only 2 dimensions, and the Brief Medication Questionnaire (used in 3 studies) measured 3 dimensions and 2 phases. Distinctions between intentional and nonintentional factors were not completely considered in any scale. CONCLUSIONS: Although multiple studies target medication adherence in PD, the used scales did not measure all recommended components, highlighting the need to develop a sensitive, specific, and comprehensive tool for measuring medication adherence among patients with PD.