Responsiveness of impairments and disabilities in Parkinson's disease.

The objective of this study is to evaluate the responsiveness of items of the Activities of Daily Living (ADL) and Motor section of the Unified Parkinson's Disease Rating Scale (UPDRS) in patients with Parkinson's Disease (PD). A standardized Response Mean (SRM) per item was calculated using data of four trials (n=376) that randomised patients with early PD to dopamine agonist (DA) monotherapy or placebo. In the ADL section, the SRMs ranged from -0.04 (no effect) to -0.50 (moderate effect). Hand functions were the most responsive ADL items with 'handwriting' showing the largest response. Self-assessed symptoms were the least responsive. In the Motor section, SRMs ranged from -0.09 to -0.60 with bradykinesia items showing the largest response, especially the item 'finger taps'. The tremor items showed the smallest response, however, rest tremor arms was much more responsive than rest tremor of the head and legs or postural tremor. SRMs in the placebo group ranged from 0.08 to -0.21 in the ADL section and from 0.03 to -0.35 in the Motor section. ADL and motor items have comparable and mostly small effect sizes. The most responsive items are in the ADL section hand functions and in the Motor section bradykinesia items. A more responsive ADL section would omit the self-assessed symptoms and the Motor section would retain only rest tremor arms of the tremor items.