Validation of the International Parkinson and Movement Disorder Society Non-Motor Symptoms Questionnaire (MDS-NMS-Q)

Background: The Movement Disorder Society Non-Motor Rating Scale (MDS-NMS) assesses severity and frequency of non-motor symptoms (NMS) in Parkinson's disease (PD) and is rater-administered. The MDS-NMS Questionnaire (MDS-NMS-Q), developed as a briefer (i.e., assessing symptom severity only), self-completed version of the MDS-NMS, is also a 13-domain, 52-symptom instrument with a separate non-motor fluctuations (NMFs) section. // Objective: The goal was to validate the MDS-NMS-Q versus the MDS-NMS. // Methods: A cross-sectional, multi-site, international study was conducted with idiopathic PD patients. After completing the self-administered MDS-NMS-Q unsupervised, patients were assessed with the rater-administered MDS-NMS. // Results: The cohort consisted of 199 PD patients (mean age [±standard deviation (SD)] = 67.19 [±9.95] years; mean age at PD diagnosis [±SD] = 59.27 [±9.54] years); median Hoehn and Yahr stage = 2. Data quality was satisfactory for all 13 MDS-NMS-Q domains. There were no floor or ceiling effects for the total score; individual domains had no appreciable ceiling effects, but variable floor effects (5.0%–71.4%). Internal consistency for most domains was satisfactory, except for the impulse control domain (Cronbach's α ≥0.75 for 10/13 domains). Correlation and concordance between MDS-NMS-Q and MDS-NMS total scores were high (Spearman rank correlation coefficient = 0.86; Kendall's coefficient of concordance = 0.93). // Conclusions: The MDS-NMS-Q has a strong association and concordance with the MDS-NMS at the total score and domain level. This indicates that the MDS-NMS-Q, allowing self-completion and focusing only on symptom severity, is an acceptable alternative to rater administration assessing both severity and frequency.