Rating Scales for Medication Adherence in Parkinson's Disease: A Systematic Review for Critique and Recommendations

Behaviors interfering with medication adherence (MA) are common and often complex in Parkinson's disease (PD), negatively affecting quality of life and undermining the value of clinical trials. The Clinical Outcome Assessments (COA) Scientific Evaluation Committee of the International Parkinson and Movement Disorder Society (MDS) commissioned the assessment of MA rating scales to recommend the use in PD.

Critically review the measurement properties of rating scales used to assess MA in PD and to issue recommendations.

We conducted systematic review across seven databases to identify structured scales to assess MA in PD. Eligible studies were critically appraised for methodological quality using the Consensus-based Standards for the Selection of Health Measurement Instruments (COSMIN) Risk of Bias checklist. Standards for good measurement properties of the selected scales were summarized narratively using the COSMIN, the MDS-COA Committee methodology, the World Health Organization concepts, and the Ascertaining Barriers to Compliance taxonomy. The certainty of the evidence was determined using the modified Grades of Recommendation, Assessment, Development and Evaluation approach with final assessments (highest to lowest) of "Recommended," "Suggested" and "Listed".

Of the nine reviewed scales, none met the designation "Recommended". The Morisky Medication Adherence Scale (MMAS-8); Beliefs Related to Medications Adherence questionnaire, Beliefs about Medication Questionnaire, Medication Adherence Rating Scale, and Satisfaction with Information on Medicines Scale were rated "Suggested".

We suggest further work focusing on resolving the problems of the suggested scales or developing a new scale meeting all required criteria.