Objective: To test whether The Movement Disorder Society revision of the Unified Parkinson’s Disease Rating Scale (MDS-UPDRS) Part III (Motor Examination) items provide increased sensitivity to mild motor signs when compared to the same items of the Unified Parkinson’s Disease Rating Scale (UPDRS) in a sample of de novo Parkinson’s disease (PD) patients.

Background: The MDS-UPDRS was designed to be more sensitive to mild motor severity than the original UPDRS. However, this has not been previously studied in patients with early PD.

Method: We analyzed a sample from the Study in PD of Exercise (SPARX) ⁽¹⁾ of 129 de novo PD patients assessed at one time point simultaneously with both scales. We compared the scores on the 17 items that measure the same motor function in both scales modeling the data using the method outlined by Goetz et al ⁽²⁾ for the cross-mapping of items, scaling anchors and conversion of scores from the original UPDRS to the MDS-UPDRS. The scaling anchors for the MDS-UPDRS were Slight, Mild, Moderate and Severe. The scaling anchors for the UPDRS were Mild, Moderate, Severe and Marked. Using Classical Test Theory (CTT), we compared the distributions of the scaling anchors from the individual items of both scales. Using Item Response Theory (IRT) we examined the sensitivity of each scaling anchor from each scale to the latent-trait measurement of overall parkinsonian motor severity.

Results: Of the 2193 observations of individual scaling anchors from the 17 items in both versions of the scale, the majority of response option observations, with scaling anchors differing between the scales, was represented by a score of 1 (19.2%). There was a sparse representation of scores of 3 and 4 across the two scales. From the CTT approach, we found frequent floor effects for both scales. The only item that demonstrated a significance difference in the scaling distribution between the two versions of the scale was the item assessing Gait (p=0.005). IRT analyses revealed similar levels of sensitivity to the latent trait of PD motor function.

Conclusion: The combined results of this study do not support increased sensitivity of MDS-UPDRS compared to the UPDRS for assessing mild motor severity in de novo PD patients in most items. The only exception to this was significant difference in the scaling for the item assessing gait.

References: 1. Moore CG, Schenkman M, Kohrt WM, Delitto A, Hall DA, Corcos D. Study in Parkinson Disease of Exercise (SPARX): Translating high-intensity exercise from animals to humans. Contemp Clin Trials. 2013;36(1):90–8. 2. Goetz CG, Tilley BC, Shaftman SR, Stebbins GT, Fahn S, Martinez-Martin P, et al. Movement Disorder Society-sponsored revision of the Unified Parkinson’s Disease Rating Scale (MDS-UPDRS): Scale presentation and clinimetric testing results. Mov Disord. 2008;23(15):2129–70.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/does-mds-updrs-provide-greater-sensitivity-to-mild-disease-than-updrs-for-assessing-motor-severity-in-early-parkinsons-disease/