Objective: To test whether the patient-derived MDS-UPDRS Parts assessing non-motor (Part 1) and motor (Part 2) functional impact of PD can be summed to render a summary score for motor and non-motor experiences of PD from a patient perspective.

Background: The MDS-UPDRS is a comprehensive tool for assessing motor and non-motor aspects of Parkinson’s disease (PD) through patient and investigator ratings.  FDA guidelines highlight integrating patient perspectives in clinical outcome assessments with objective ratings.

Method: Using 7,466 complete MDS-UPDRS exams, we summed patient questionnaire data [Part 2 with Part 1B or Part 2 + Part 1A and 1B, the latter combining Interview (1A) and Questionnaire (1B) data.. For each of the two summed combinations, we conducted an exploratory factor analysis (EFA) to determine the number of factors, based on the number of eigenvalues being at least 1 in the scree plot. We then conducted a confirmatory factor analysis (CFA) to evaluate the construct validity of the identified factor structure. The goodness-of-fit index was determined using the comparative fit index (CFI), with a CFI > 0.90 indicating an acceptable fit, consistent with the initial validation of the MDS-UPDRS.

Results: To assess the construct validity of the factor structures for the two tested combinations, we selected two factors for the combination of Parts 1+2 and one factor for Parts 1B+2, respectively, based on eigenvalues greater than 1 on the scree plots. The CFA results indicated that the CFIs for both combinations were higher than the pre-specified validity threshold of 0.90 (0.944 for Parts 1+2 and 0.939 for Parts 1B+2) and therefore confirmed validity.

Conclusion: This study provides strong statistical confirmation for the use of combined sum-scores of MDS-UPDRS Parts 1 and 2, representing a comprehensive evaluation of motor and non-motor experiences of PD according to patient reports.  Our findings directly respond to the FDA’s call for incorporation of the patient voice into outcomes research and underscore the robustness of the MDS-UPDRS.

References: Zou H, Goetz CG, Stebbins GT, Schrag A, Mestre TA, Luo S. Summing MDS-UPDRS parts 1+ 2 (non-motor and motor experience of daily living): the Patient’s voice. Movement disorders: official journal of the Movement Disorder Society. 2023 Jul;38(7):1363.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/combining-mds-updrs-parts-1-and-2-using-the-patients-voice/