Longitudinal Evaluation of an Abbreviated Patient-Reported Movement Disorder Society-sponsored revision of the Unified Parkinson's Disease Rating Scale (MDS-UPDRS) for Predicting Dopaminergic Therapy Initiation in Early Parkinson's Disease.

BACKGROUND

Predicting initiation of dopaminergic therapy in early Parkinson's disease (PD) is important for clinical management and trial design. Prior cross-sectional work identified a six-item patient-reported subset from the Movement Disorder Society-sponsored revision of the Unified Parkinson's Disease Rating Scale (MDS-UPDRS) Parts IB + II, but its longitudinal utility is unknown.

OBJECTIVES

To test whether modeling longitudinal symptom trajectories improves prediction of dopaminergic therapy initiation beyond baseline-only models, and to identify an abbreviated patient-reported subset with stable prognostic value and utility for trial stratification.

METHODS

Data were harmonized from 1787 untreated early PD patients across six multicenter studies. All 20 MDS-UPDRS Parts IB + II items were analyzed using a longitudinal item response theory model. Items were ranked by discrimination and information functions, and cumulative subsets evaluated in Cox models with time-dependent covariates, adjusted for age, sex, disease duration, and Hoehn and Yahr stage. Predictive accuracy was quantified by concordance index (C-index) for full follow-up and truncation at 1 and 2 years. Risk stratification was assessed based on baseline abbreviated subset scores using Kaplan-Meier analyses.

RESULTS

An 11-item model consistently outperformed the full 20-item scale (C-index 0.609 vs. 0.597, P < 0.001 with full follow-up; 0.621 vs. 0.599, P < 0.001 at 1 year; 0.615 vs. 0.602, P < 0.001 at 2 years). Longitudinal updates improved discrimination over baseline-only models (eg, 0.609 vs. 0.594 for full follow-up). Higher baseline 11-item scores were strongly associated with earlier therapy initiation.

CONCLUSIONS

Longitudinal symptom modeling improves prediction of therapy initiation in early PD. An abbreviated 11-item patient-reported MDS-UPDRS provides stronger prognostic value than the full scale and supports trial stratification and clinical monitoring. © 2025 International Parkinson and Movement Disorder Society.