Rankin scale as a potential measure of global disability in early Parkinson's disease

Abstract

We conducted an exploratory analysis of the utility of the modified Rankin Scale (mRS) as a global measure of disability in early Parkinson's diesase (PD) using the baseline data from a large cohort of PD patients enrolled in a longitudinal study of creatine. The mRS is scored 0-6 with lower scores reflecting less disability. For the analysis the mRS score was dichotomized at <2 versus ≥2. We explored the association of the mRS with multiple measures of PD-related impairments, including the Unified Parkinson Disease Rating Scale (UPDRS); cognitive function characterized by the Symbol Digit Modalities--verbal, and Scales for Outcomes in Parkinson's disease--cognition (SCOPA-COG); quality of life (Parkinson's disease questionnaire [PDQ-39]) and EuroQOL; Beck Depression Inventory II (BDI); and Total Functional Capacity (TFC). We also investigated the interaction between variables. One thousand seven hundred forty-one patients were included in the analysis of which 374 had a mRS score of 2 or above. In the univariate model, all interested measures except SCOPA-COG (p=0.23) had significant association with mRS (p<0.001) after controlling for confounders. In the multivariate model, UPDRS Part II and III (activities of daily living and motor), BDI, TFC and PDQ-39 were significant (p<0.05). The mRS has a significant association with the wide spectrum of measures of impairment and quality of life in early PD and shows good potential to be a global measure of disability in early PD. The sensitivity of the mRS to change and performance of the scale in more advanced PD will have to be established longitudinally.

Keywords: Clinical trials; Clinical trials methodology; Parkinson’s disease; Rankin scale.