Comment on “Summing MDS-UPDRS Parts 1 + 2 (Nonmotor and Motor Experience of Daily Living): The Patient's Voice”

We read with great interest the article by Zou and colleagues titled “Summing MDS-UPDRS Parts 1 + 2 (Nonmotor and Motor Experience of Daily Living): The Patient's Voice.”¹ In the past few years, the Movement Disorder Society–sponsored revision of the Unified Parkinson's Disease Rating Scale (MDS-UPDRS),² developed according to clinimetric guidelines and validated in several languages,³ has become an integral part of clinical practice and research. Although until recently the development team had recommended separate scoring of the four parts of the scale, in clinical practice it seemed a logical step to combine some parts into a composite score.⁴ In addition to the total score, such a measure could be a composite score measuring activities of daily living of the patients as defined by motor and nonmotor symptoms (summation of parts 1 + 2) or a composite scale measuring the severity of movement-related symptoms and their impact on activities of daily living (summing up parts 2 + 3). However, the use of composite scores may be implicit, and the development team has so far recommended a strictly separate assessment of each part of the score.^{1, 2} This approach to separate assessment of the subscales is fundamentally changed by the new US Food and Drug Administration guidance, which prioritizes the integration of patient opinion into an objective measure.⁵ According to this new perspective, the authors of the referenced article propose basically two types of integration summarizing parts 1 + 2 and 1B + 2.¹ They consider that both are in line with the criteria for clinimetric methods.

In our comment, we draw attention to the fact that the usefulness of these composite calculations seems to be justified by the application of other techniques. Because the calculated scores are used not only to characterize the degree of severity or disability but also to assess changes over time, progression or the effectiveness of the therapeutic response, it is of high importance that the newly developed composite scales track these changes well and a reliable metric found to assess improvement or deterioration that highlights clinical significance.

Minimal clinically important differences (MCID) are defined as the smallest cutoff values that can separate clinically relevant changes from clinically unimportant or negligible changes. MCID cutoff values are typically asymmetric, that is, the cutoff value for the smallest clinically relevant improvement and the smallest clinically relevant worsening on a given scale is not always the same. In 2017, our workgroup attempted to define MCID cutoffs for the MDS-UPDRS Experiences of Daily Living Parts.⁶ Our work demonstrated that the MCID can be calculated not only separately for parts 1 and 2 but also reliably for the 1 + 2 composite scale. We have shown that any improvement of more than 5.7 points or a deterioration of at least 4.7 points can be considered as a measure of clinical relevance for the 1 + 2 composite scale.⁶

This study also seems to confirm the finding of Zou and colleagues that the 1 + 2 composite scale is a useful tool for measuring the voice of patients in clinical practice. In our opinion, such composite measures for the Unified Dyskinesia Rating Scale are also warranted.⁷

(1) Manuscript: A. Writing of the First Draft, B. Review and Critique.

N.K.: 1A, 1B

Z.A.: 1B

M.H.: 1B

M.R.: 1B

J.J.: 1B

D.P.: 1A, 1B

N.K. received less than 1000 EUR consultation fees from Hungarian subsidiaries of Medtronic, Boehringer Ingelheim, Novartis, GlaxoSmithKline, UCB, Krka, and AbbVie. Regarding this work, the author did not receive any corporate funding. J.J. received less than 1000 EUR consultation fees from Hungarian subsidiaries of UCB, Richter, and Gerot. Regarding this work, the author did not receive any corporate funding. Z.A., M.H., M.R., and D.P. have nothing to disclose.