Objective: (1) Construct a measure of ambulatory capacity derived from the MDS-UPDRS that is similarly structured to the original Ambulatory Capacity Measure (ACM) derived from the UPDRS; (2) Determine associations between longitudinal measures of ambulatory capacity with disease progression and disability measures; (3) Compare ambulatory capacity measures in dopaminergic-treated OFF/ON states.

Background: Impaired ambulation is a major source of disability in Parkinson’s disease (PD). The ACM is a construct to measure gait and ambulation ability in PD, derived as the sum of the scores of the original UPDRS items 13 (falling), 14 (freezing), 15 (walking), 29 (gait), and 30 (postural stability). The contemporary MDS-UPDRS differs from the UPDRS in scaling and some individual items. There is no congruent measure of ambulatory capacity using the MDS-UPDRS.

Method: An updated ACM (uACM) was constructed from MDS-UPDRS items 2.13 (freezing), 2.12 (walking and balance), 3.10 (gait), 3.12 (postural stability), and 3.11 (freezing of gait). ACM and uACM scores were calculated and compared using annual UPDRS and MDS-UPDRS paired assessments from a phase 3 clinical trial of isradipine that spanned 36-months. Correlations between uACM scores with Schwab & England Activities of Daily Living (ADL), Hoehn & Yahr (HY), and modified Rankin (mRank) scores over 36 months were assessed by repeated measures correlation coefficients (r_rm). OFF/ON states of longitudinal uACM scores were also compared in dopaminergic-treated participants from the Parkinson’s Progression Marker Initiative cohort.

Results: The mean (standard deviation) difference between paired ACM and uACM scores was 0.047 (0.860; paired t-test p=0.053). The r_rm [95% CI] between uACM with ADL, HY, and mRank was -0.30 [-0.36, -0.24], 0.31 [0.25, 0.37], and 0.32 [0.26, 0.38], respectfully (p<0.001). Mean differences in paired OFF and ON uACM scores were 0.25 (0.67), 0.25 (0.56), 0.34 (0.69), and 0.30 (0.74) at annual visits (months 12 – 48), and were not significantly different across time points (ANOVA p=0.62), despite mean increases in levodopa equivalent dose from 270mg to 560mg across the same time.

Conclusion: Longitudinally, as uACM gradually increases, disease progression and disability tend to worsen, and OFF/ON uACM score differences are steady and minimal. uACM scores will be assessed in more advanced cohorts.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/ambulatory-capacity-measure-derived-from-the-movement-disorders-society-unified-parkinsons-disease-rating-scale-mds-updrs/