Rasch-Built Overall Disability Scale for Chronic Idiopathic Axonal Polyneuropathy

Area of Science:

• Neurology
• Clinical Measurement
• Health Outcomes Research

Background:

• Chronic idiopathic axonal polyneuropathy (CIAP) is a prevalent condition impacting patient quality of life.
• A significant gap exists in patient-reported outcome measures specific to CIAP functional deficits.
• Existing measures do not adequately capture the functional impact of CIAP.

Purpose of the Study:

• To develop and validate a patient-reported, Rasch-built interval scale for assessing disability in CIAP patients.
• To create a disease-specific measure for activity and participation limitations in CIAP.
• To establish a reliable and valid tool for CIAP outcome assessment.

Main Methods:

• Development of a preliminary 196-item scale (pre-CIAP-RODS) using ICF and expert-derived items.
• Rasch analysis (RUMM2030+) applied to refine the scale based on patient-reported difficulty scores.
• Test-retest reliability and external validity assessment using EQ-5D-3L.

Main Results:

• A 24-item CIAP-RODS was developed, meeting Rasch model requirements after systematic item reduction.
• The final CIAP-RODS demonstrated good test-retest reliability and robust internal validity (PSI=0.95).
• Significant associations with EQ-5D-3L scores confirmed good discriminative external validity.

Conclusions:

• The 24-item CIAP-RODS is a validated, disease-specific measure for activity and participation limitations in CIAP.
• Recommended for use in future studies to monitor longitudinal changes in CIAP.
• Further research is needed to establish responsiveness and cross-cultural validity.