Item Response Model Adaptation for Analyzing Data from Different Versions of Parkinson’s Disease Rating Scales

PURPOSE: The aim of this work was to allow combination of information from recent and historical trials in Parkinson’s Disease (PD) by developing bridging methodology between two versions of the clinical endpoint. METHODS: A previously developed Item Response Model (IRM), that described longitudinal changes in Movement Disorder Society (MDS) sponsored revision of Unified Parkinson’s Disease Rating Scale (UPDRS) [MDS–UPDRS] data from the De Novo PD cohort in Parkinson’s Progression Markers Initiative, was first adapted to describe baseline UPDRS data from two clinical trials, one in subjects with early PD and another in subjects with advanced PD. Assuming similar IRM structure, items of the UPDRS version were mapped to those in the MDS-UPDRS version. Subsequently, the longitudinal changes in the placebo arm of the advanced PD study were characterized. RESULTS: The parameters reflecting differences in the shared items between endpoints were successfully estimated, and the model diagnostics indicated that mapping was better for early PD subjects (closer to De Novo cohort) than for advanced PD subjects. Disease progression for placebo in advanced PD patients was relatively shallow. CONCLUSION: An IRM able to handle two variants of clinical PD endpoints was developed; it can improve the utilization of data from diverse sources and diverse disease populations. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s11095-019-2668-6) contains supplementary material, which is available to authorized users.