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Rasch-Built Overall Disability Scale for IgM-Associated Polyneuropathy With and Without Anti-MAG Antibodies: IgM-RODS
Tatiana Hamadeh1, Johannes P M van de Mortel2, Janneke G J Hoeijmakers1
1Department of Neurology, Maastricht University Medical Center+, Mental Health and Neuroscience Research Institute, Maastricht, the Netherlands.
Background And Aim:
IgM monoclonal gammopathy-associated polyneuropathy with(out) anti-myelin associated glycoprotein (±anti-MAG) is a rare immune-mediated disease that may cause severe limitations in daily activities and quality of life. The absence of a systematic comparison between patients with/without anti-MAG IgM polyneuropathy, no disease-specific functional metric, and lack of international consensus regarding assessment and treatment of these patients are factors obstructing future clinical trials. Therefore, it was decided to develop an interval Rasch-built activity/participation scale specifically for IgM polyneuropathy ±anti-MAG (IgM-RODS) and examine its clinimetric properties.
Methods:
A pre-phase IgM-RODS questionnaire containing 146 activity/participation items, based on the WHO International Classification of Functioning, Disability and Health, was completed by participants (≥ 18 years) of the IMAGiNe observational registry that fulfilled international criteria for IgM-polyneuropathy ±anti-MAG. Data was subjected to Rasch analyses, and reliability/validity studies were performed as well.
Results:
The pre-RODS data of 259 subjects (originating from 8 different countries) underwent quality assessment, and 244 remaining records were submitted to the Rasch model, evidencing the model's expectations. Based on requirements like exceeding fit residuals, misfit statistics, item bias, local dependency, and less face validity, we systematically removed items until the final 36-item IgM-RODS fulfilled all Rasch requirements and showed acceptable test-retest reliability, cross-cultural, construct and discriminant validity, and unidimensionality. Compared to the Inflammatory-RODS, the IgM-RODS showed lower standard errors across the metric, indicating greater sensitivity.
Interpretation:
The 36-item IgM-RODS is a disease-specific interval measure suitable for detecting functional deficits in patients with IgM-polyneuropathy ±anti-MAG. Future studies are needed to determine its responsiveness.
Insights
A new 36-item scale, the IgM-RODS, effectively measures functional deficits in patients with IgM polyneuropathy ±anti-MAG. This disease-specific tool enhances assessment for this rare immune-mediated condition.
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.
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