Independent validation of the Non motor Symptoms Scale for Parkinson's disease in Brazilian patients

Objective: Independent validation of the Non motor Symptoms Scale in Parkinson's disease (NMSS) based on a cross-culturally adapted Brazilian version. Methods: Parkinson's disease (PD) patients were evaluated by means of the Scales for Outcomes in Parkinson's disease-Motor (SCOPA-M), Autonomic, Cognition, and Psychosis; Hoehn and Yahr staging (H & Y); Berg Balance Scale; PD Sleep Scale; Clinical Impression of Severity Index for PD (CISI-PD); PDQ-39; and EQ-5D. The following clinimetric attributes were explored for the NMSS: acceptability, scaling assumptions, reliability, construct validity, and precision. Results: 150 patients were assessed (mean age 63.1 years; 56.7% males; mean duration of illness 8.7 years; HY median: 2). Mean NMSS was 48.9 (SD 36.3; median 42; skewness 1.3). Neither floor nor ceiling effect was observed on the NMSS total score. For domains, the Cronbach's alpha coefficient ranged from 0.40 to 0.82. The NMSS total score correlated significantly with SCOPA-AUT (r(S) = 0.65) and with those scales measuring related constructs (r(S) = 0.46-0.57). NMSS significantly increased as the H&Y stage increased (Kruskal-Wallis, p < 0.0001). These values were quite close to those from the original validation studies. Conclusions: The NMSS is a reliable and valid measure to evaluate non motor symptoms in Brazilian PD patients. (C) 2012 Elsevier Ltd. All rights reserved.