Conversion between NMSS and MDS‐NMS in Parkinson's Disease

Abstract Background The burden of non‐motor symptoms in Parkinson's disease (PD) can be measured with the Non‐Motor Symptoms Scale (NMSS) and the International Parkinson and Movement Disorder Society Non‐Motor Rating Scale (MDS‐NMS), for which scoring systems, structure and clinical coverage differ. Objectives The goal was to develop conversion formulas between the NMSS and the MDS‐NMS scores. Methods Data from 402 patients with PD participating in the primary MDS‐NMS validation study were used. The association between domain and total scores of both scales was assessed by the Spearman rank correlation coefficient and Kendall's W concordance coefficient. Equations for between‐scale transformation of total score were constructed from weighted linear regression models. Results Spearman rank correlations showed that MDS‐NMS domains correlated 0.39 to 0.88 with the corresponding NMSS domains. The equation for transforming the NMSS total score to MDS‐NMS total score is: MDS‐NMS = 11.629 + 1.624 × NMSS ( P < 0.001, R 2 = 0.748). For converting the MDS‐NMS total score to NMSS total score, the formula is NMSS = 2.475 + 0.495 × MDS‐NMS ( P < 0.001, R 2 = 0.771). Conclusions Our conversion equations enable direct comparison of the NMSS and MDS‐NMS instruments, facilitating data comparability across studies. © 2025 International Parkinson and Movement Disorder Society.