Objective: To provide a comprehensive review of various patient-reported outcome (PROs) used in movement disorders (MD) research and their MCID values reported in literature.

Background: There is a growing awareness of significance of using MCID in MD research. MCID is the smallest change in an outcome measure that is considered clinically meaningful. MCID can ensure trials are adequately powered to detect meaningful treatment effects, aid in interpretation of treatment outcomes, and development of new outcome measures, and aid in  selection of appropriate endpoints.[1],[2],[3]

Method: Inclusion criteria:(a) studies published in English,(b) studies reporting MCID scales, and(c) studies reporting on one or more movement disorders, including Parkinsonism, Dystonia, tremor, tics, dyskinesia, tardive, or chorea. Databases searched included PubMed, Embase and MEDLINE.

Results: Final review included 31 studies[Figure1]. Among the 10 RCTs included, majority(n=6) had low risk of bias (RoB),2 had high RoB and 2 had some concerns.[4][5][Figure2] Among the remaining non-RCTs, majority showed low RoB in all domains of JBI tool, except for domain of consecutive enrolment of patients (domain no. 4 ) and site of study (domain no.9).[6][Figure3] Overall the included studies were of good quality. There was considerable variability in the MD studied as well as the scales used. MCID values were most commonly reported for UPDRS scale (n=11, MCID ranging from 1.8 to 8 points for various subsections of UPDRS for improvement (IMP) and from 2 to 10.7 points for worsening(WOR)). 3 studies each reported on AIMS (MCID 2-3 points), PDQ 39 (MCID IMP 1.6 to 4.7; WOR 2.6 to 4.2 points), PDQ 8 ( MCID IMP 5.9 to 9.2; WOR 4.9 to 7.4 points), and UDysRS (MCID: IMP >1.8 to 2.1; WOR >1.8 to >1.7).[Table1,2][7-37]

Conclusion: The review is significant in that it combines all MCID scales currently reported in MD patients, for the first time in literature, providing a comprehensive resource for future trials. This review highlights the need for standardized and validated MCID scales in MD research to help clinicians and researchers interpret study results and to make informed decisions about patient care. MCID scales can also help to ensure that future MD trials are designed and conducted in a way that is most meaningful and relevant to patients.

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