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Updated: Oct 17, 2025
Dynamic Digital Biomarkers of Motor and Cognitive Function in Parkinson's Disease
Published on: July 24, 2019
Does MDS-UPDRS Provide Greater Sensitivity to Mild Disease than UPDRS in De Novo Parkinson's Disease?
Michelle H S Tosin1,2, Glenn T Stebbins2, Cynthia Comella2
1Department of Nursing Fluminense Federal University Niteroi Brazil.
Background:
The Movement Disorder Society revision of the Unified Parkinson's Disease Rating Scale (MDS-UPDRS) was designed to be more sensitive to mild motor severity than the Unified Parkinson's Disease Rating Scale (UPDRS).
Objective:
To test whether MDS-UPDRS Part III items provide increased sensitivity to mild motor severity when compared to the same items of the UPDRS in de novo PD patients.
Method:
Using a sample of 129 de novo PD patients assessed at one time point simultaneously with both scales, we compared the scale's scores on the 17 items measuring the same motor function. The scaling anchors for the MDS-UPDRS were Slight, Mild, Moderate and Severe, and 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. Using Item Response Theory (IRT), we examined the sensitivity of the scaling anchors from each scale to the latent-trait measurement of overall parkinsonian motor severity.
Results:
There was 2193 observations of individual scaling anchors from the 17 items in both scales. The CTT approach revealed frequent floor effects with only the item assessing Gait demonstrating a significance difference in the scaling distribution between the scales (P = 0.005). The IRT analyses revealed similar levels of sensitivity to the latent trait of PD motor function.
Conclusion:
These results do not support increased sensitivity of MDS-UPDRS over the UPDRS for assessing mild motor severity in de novo PD patients, with significant difference in the scaling only for the item assessing gait.
Insights
The Movement Disorder Society revision of the Unified Parkinson's Disease Rating Scale (MDS-UPDRS) does not show increased sensitivity for mild motor symptoms in early Parkinson's disease compared to the original UPDRS. Only gait assessment differed significantly between the scales.
Area of Science:
- Neurology
- Movement Disorders
- Clinical Assessment
Background:
- The Movement Disorder Society revision of the Unified Parkinson's Disease Rating Scale (MDS-UPDRS) was developed to enhance sensitivity to mild motor impairments in Parkinson's disease (PD).
- The original Unified Parkinson's Disease Rating Scale (UPDRS) has been a standard but may lack precision in detecting early-stage motor deficits.
Purpose of the Study:
- To evaluate if the MDS-UPDRS Part III items offer greater sensitivity to mild motor severity compared to equivalent items in the UPDRS.
- To assess the performance of both scales in a cohort of newly diagnosed (de novo) Parkinson's disease patients.
Main Methods:
- A cohort of 129 de novo PD patients were assessed simultaneously using both the MDS-UPDRS and UPDRS.
- Classical Test Theory (CTT) and Item Response Theory (IRT) were employed to compare the scaling anchors and sensitivity of 17 motor items common to both scales.
- Scaling anchors differed, with MDS-UPDRS using Slight, Mild, Moderate, Severe and UPDRS using Mild, Moderate, Severe, Marked.
Main Results:
- Analysis of 2193 observations revealed frequent floor effects across most items in both scales.
- Classical Test Theory (CTT) showed a significant difference in scaling distribution only for the gait item (P=0.005).
- Item Response Theory (IRT) analyses indicated comparable sensitivity of both scales to the underlying motor severity in Parkinson's disease.
Conclusions:
- The study findings do not substantiate the hypothesis that the MDS-UPDRS exhibits superior sensitivity over the UPDRS for evaluating mild motor severity in de novo PD patients.
- A significant difference in scaling between the two instruments was observed solely for the item assessing gait.
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