The Development of a Quantitative Disability Assessment Tool in Patients with Idiopathic Parkinson's Disease

Background/Objectives: The objective of this study was to develop a novel quantitative disability assessment tool for patients with idiopathic Parkinson's disease (IPD). Methods: A total of 47 patients with IPD were recruited from two hospitals. A specialist in Rehabilitation Medicine utilized the modified Schwab and England Activities of Daily Living Scale (mSEADL) as a reference, conducting a comprehensive medical chart review and an in-depth interview. The novel-developed disability measurement was calculated as ((mSEADL during the on-state) × (time of on-state)) + ((mSEADL during the off-state) × (time of off-state))/(waking time). Additionally, the degree of disability was assessed using the Korean version of the Modified Barthel Index during the on-state. Results: Twenty-four participants (51.1%) exhibited the off-state during waking hours. In patients exhibiting an off-state, the mSEADL score was significantly lower during the off-state than during the on-state (p < 0.05). The novel-developed disability measurement demonstrated a higher correlation coefficient with the reference mSEADL (0.960) than with the K-MBI (0.808), with statistical significance (p < 0.05). Conclusions: The results demonstrated that larger IPD patients exhibited an on-off phenomenon with greater dependency during the off-state. Therefore, the on-off phenomenon should be considered when evaluating disability in patients with IPD, with methods such as the novel-developed disability measurement tool in this study.