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. 2019 Oct;34(10):1480-1487.
doi: 10.1002/mds.27790. Epub 2019 Jul 10.

Measuring Parkinson's disease over time: The real-world within-subject reliability of the MDS-UPDRS

Luc J W Evers  1   2 , Jesse H Krijthe  2 , Marjan J Meinders  3 , Bastiaan R Bloem  1 , Tom M Heskes  2
Affiliations

Measuring Parkinson's disease over time: The real-world within-subject reliability of the MDS-UPDRS

Luc J W Evers et al. Mov Disord. 2019 Oct.

Abstract

Background: An important challenge in Parkinson's disease research is how to measure disease progression, ideally at the individual patient level. The MDS-UPDRS, a clinical assessment of motor and nonmotor impairments, is widely used in longitudinal studies. However, its ability to assess within-subject changes is not well known. The objective of this study was to estimate the reliability of the MDS-UPDRS when used to measure within-subject changes in disease progression under real-world conditions.

Methods: Data were obtained from the Parkinson's Progression Markers Initiative cohort and included repeated MDS-UPDRS measurements from 423 de novo Parkinson's disease patients (median follow-up: 54 months). Subtotals were calculated for parts I, II, and III (in on and off states). In addition, factor scores were extracted from each part. A linear Gaussian state space model was used to differentiate variance introduced by long-lasting changes from variance introduced by measurement error and short-term fluctuations. Based on this, we determined the within-subject reliability of 1-year change scores.

Results: Overall, the within-subject reliability ranged from 0.13 to 0.62. Of the subscales, parts II and III (OFF) demonstrated the highest within-subject reliability (both 0.50). Of the factor scores, the scores related to gait/posture (0.62), mobility (0.45), and rest tremor (0.43) showed the most consistent behavior.

Conclusions: Our results highlight that MDS-UPDRS change scores contain a substantial amount of error variance, underscoring the need for more reliable instruments to forward our understanding of the heterogeneity in PD progression. Focusing on gait and rest tremor may be a promising approach for an early Parkinson's disease population. © 2019 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Keywords: MDS-UPDRS; Parkinson's disease; disease progression; modeling; reliability.

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Figures

Figure 1
Figure 1
Correlation between two subsequent 1‐year change scores of the MDS‐UPDRS part III (OFF) on the PPMI data set. Line is fitted by linear regression on the response variable y3‐y2. A similar negative correlation can be seen in parts I, II, and III (ON).
Figure 2
Figure 2
Left: number of assessments included in the analysis for each part and on each visit. Middle: progression of the subscales on a group level (median, 10%, and 25% around the median are shown; missing values were excluded). Right: illustration of the individual progression of the subscale scores (8 illustrative examples of cases with <2 missing values are shown).
Figure 3
Figure 3
Graphical presentation of the MDS‐UPDRS progression model, as applied to each individual subject denoted by the indices i.
See this image and copyright information in PMC

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