The symptom inventory disability-specific short forms for multiple sclerosis: reliability and factor structure.

Area of Science:

• Neurology
• Psychometrics
• Clinical Research

Background:

• The Symptom Inventory (SI) is a 99-item measure for multiple sclerosis (MS).
• Modern test theory methods can refine existing measures for better clinical utility.
• Disability varies significantly among MS patients, necessitating tailored assessment tools.

Purpose of the Study:

• To develop 3 disability-specific short forms of the SI for MS patient subgroups.
• To utilize Performance Scale (PS) items for subgroup identification.
• To apply modern test theory for enhanced measurement precision.

Main Methods:

• A web-based, cross-sectional study involving 1532 participants from the National MS Registry.
• Exploratory and confirmatory factor analysis were used to assess scale unidimensionality.
• Item response theory analyses were conducted to evaluate model fit.

Main Results:

• 14 factors were identified, aligning with the PS structure.
• Unidimensionality was confirmed for hand function, vision, fatigue, cognitive, bowel/bladder, spasticity, and pain scales.
• Mobility and sensory scales were refined, and item response theory analyses showed good model fit.

Conclusions:

• Empirical support was found for a 10-scale symptom measure for MS clinical research.
• Disability-specific short forms were created for 5 scales, with single forms for the remaining 5.
• The PS items can screen for these short forms, offering flexibility without requiring real-time computer infrastructure.