A novel Global Assessment Scale for Wilson's Disease (GAS for WD)

Abstract

Wilson's disease (WD) is an inherited disorder of copper metabolism. Despite being treatable, patients with WD suffer severe disabilities due to delay in initiation and difficulty in monitoring treatment. We propose a two tier, Global Assessment Scale for Wilson's Disease (GAS for WD) that grades the multisystemic manifestations of the disease. Tier 1 scores the global disability in four domains: Liver, Cognition and behavior, Motor, and Osseomuscular. Tier 2 is multidimensional scale for a fine grained evaluation of the neurological dysfunction. We prospectively validated this scale in 30 patients with WD. Both tiers had a high inter-rater reliability (Intraclass correlation coefficient ICC (A, 2) = 0.96-1.0). Tier 2 items were internally consistent (Cronbach's alpha = 0.89) and factorial analysis showed that 90.3% of the Tier 2 total score variance was determined by seven factors. Scores of both tiers were commensurate with the disease burden as assessed by standard disability scales (Child Pugh, UPDRS, SS3, and CGI) and satisfied criteria for validity. Longitudinal follow-up over 1.5 years showed that the scale was sensitive to clinical change. This suggests that GAS for WD is a practical tool with potential applications in management of patients, and in testing and comparison of treatment regimens.