Validation of the Italian version of the Non Motor Symptoms Scale for Parkinson's disease

•Non-motor symptoms in Parkinson's disease (PD) have great impact on quality of life.•Adequate instruments to assess Non-motor Symptoms in PD are still lacking in Italy.•Validation of Italian Non-Motor Symptoms Scale (NMSS) for PD is proposed.

ObjectiveTo validate the adapted Italian version of the Non-Motor Symptoms Scale (NMSS), a tool to assess non-motor symptoms (NMS) in Parkinson's disease (PD).MethodsA cross cultural adaptation of the NMSS into Italian and a psychometric analysis of the translated version of the NMSS was carried out in patients with PD from two university centres-affiliated hospitals. The quality of data and the acceptability, reliability and construct validity of NMSS were analyzed. The following standard scales were also applied: Hoehn and Yahr staging, Unified Parkinson's Disease Rating Scale (UPDRS) part III, Montreal Cognitive Assessment, Beck Depression Inventory, Neuropsychiatric Inventory, Epworth Sleepiness Scale, Autonomic Scale for Outcomes in Parkinson's disease-Motor, Movement Disorder Society-Sponsored Revision of the Unified Parkinson's Disease Rating Scale part I and Modified Cumulative Illness Rating Scale (CIRS). Levodopa equivalent daily dose (LEDD) was calculated.ResultsSeventy-one patients with PD were assessed (mean age years 69.8 ± 9.6 SD; 31% women; mean length of disease 6.3 ± 4.6 years; H&Y median: 2). Mean NMSS was 39.76 (SD 31.9; skewness 0.95). The total score of NMSS was free of floor or ceiling effects and showed a satisfactory reliability (Cronbach's alpha coefficient on total score was 0.72 [range for domains: 0.64-0.73], SEM value was 3.88 [½ SD = 31.90]). Significant positive correlations were found among total NMSS and other NMS standard tests, but no significant correlation appeared with UPDRS part III, CIRS and LEDD.ConclusionsThe Italian NMSS is a comprehensive and helpful measure for NMS in native Italian patients with PD.