Session Information
Date: Wednesday, September 25, 2019
Session Title: Non-Motor Symptoms
Session Time: 1:15pm-2:45pm
Location: Agora 3 West, Level 3
Objective: This study aims at describing the measurement properties of the Non-motor Fluctuations (NMFs) subscale of the Movement Disorders Society Non-Motor Rating Scale (MDS-NMS) according to the Rasch model.
Background: The NMFs subscale of the MDS-NMS consists of 8 items that assess changes, in a 0-4 response scale, in non-motor symptoms (NMS) in relation to the timing of anti-parkinsonian medications.
Method: Neurologists with experience in movement disorders applied the scale to a consecutive sample of 165 patients, 84 from UK and 81 from the USA. All patients had Parkinson’s disease and NMFs. The following measurement properties were analyzed according to the Rasch model, using the RUMM2030 software: fit to the Rasch model, unidimensionality, suitability of the responses scale (threshold ordering), item local independency, reliability (Cronbach’s alpha and Personal Separation Index [PSI]), and differential item functioning (DIF) by age, sex and country.
Results: The scale showed an adequate fit to the Rasch model: chi-square(18)=33.68, p = 0.01. The scale was unidimensional, with item local independency, low PSI (0.52) but adequate Cronbach’s alpha (0.84). No item presented DIF by age, sex or country, except the item depression, which showed DIF by country (i.e., for the same depression level, UK patients showed higher ratings than USA patients did).
Conclusion: The NMFs subscale of the MDS-NMS presents good measurement properties. Further studies are needed to confirm if the depression item presents a cross-cultural bias. Linear scores obtained from Rasch analysis of this scale may be used to calculate change scores.
References: Martinez-Martin P, Schrag A, Weintraub D, Rizos A, Rodriguez-Blazquez C, Chaudhuri KR, on behalf of the IPMDS Non Motor PD Study Group. Pilot study of the International Parkinson and Movement Disorder Society- sponsored Non-Motor Rating Scale (MDS-NMS). Mov Disord Clin Practice 2019 (in print).
To cite this abstract in AMA style:
MJ. Forjaz, A. Ayala, C. Rodriguez-Blazquez, A. Schrag, D. Weintraub, A. Rizos, KR. Chaudhuri, P. Martinez-Martin. Measurement properties of the MDS-NMS Non-motor Fluctuations Subscale [abstract]. Mov Disord. 2019; 34 (suppl 2). https://www.mdsabstracts.org/abstract/measurement-properties-of-the-mds-nms-non-motor-fluctuations-subscale/. Accessed May 16, 2025.« Back to 2019 International Congress
MDS Abstracts - https://www.mdsabstracts.org/abstract/measurement-properties-of-the-mds-nms-non-motor-fluctuations-subscale/