Rasch-Built Overall Disability Scale for IgM-Associated Polyneuropathy With and Without Anti-MAG Antibodies: IgM-RODS

Area of Science:

• Neurology
• Clinical Measurement
• Immunology

Background:

• IgM monoclonal gammopathy-associated polyneuropathy (±anti-MAG) is a rare immune-mediated disorder causing significant functional limitations.
• Lack of disease-specific metrics and consensus hinders clinical trials for this condition.

Purpose of the Study:

• To develop and validate an interval Rasch-built activity/participation scale (IgM-RODS) for patients with IgM polyneuropathy ±anti-MAG.
• To establish a reliable and valid measure for assessing functional deficits in this patient population.

Main Methods:

• A 146-item pre-phase questionnaire based on the ICF was administered to patients in the IMAGiNe registry.
• Rasch analysis was employed to refine the item pool, followed by reliability and validity testing.

Main Results:

• The final 36-item IgM-RODS met Rasch model requirements, demonstrating unidimensionality.
• The scale exhibited acceptable test-retest reliability, cross-cultural, construct, and discriminant validity.
• The IgM-RODS showed greater sensitivity compared to the Inflammatory-RODS, indicated by lower standard errors.

Conclusions:

• The 36-item IgM-RODS is a disease-specific interval measure suitable for detecting functional deficits in patients with IgM polyneuropathy ±anti-MAG.
• Further research is required to evaluate the responsiveness of the IgM-RODS.