Improving assessment in small fiber neuropathy

Area of Science:

• Neurology
• Biomedical Engineering
• Psychometrics

Background:

• Small fiber neuropathy (SFN) lacks validated interval-level measures for symptoms and daily activity restrictions.
• Existing assessments do not adequately capture the full spectrum of disability in SFN patients.

Purpose of the Study:

• To develop and validate the Small Fiber Neuropathy-Overall Disability Scale (SFN-RODS©), an interval-level measure for activity and participation.
• To transform the SFN-Symptoms Inventory Questionnaire (SFN-SIQ©) into an interval-level measure.
• To establish reliable and valid tools for assessing SFN impact in clinical trials.

Main Methods:

• Rasch analysis was applied to a preliminary 146-item SFN-RODS© and a 13-item SFN-SIQ© in 238 SFN patients.
• Items were systematically removed based on Rasch model fit statistics, differential item functioning, and local dependency.
• The SFN-SIQ© was also analyzed using Rasch methodology.

Main Results:

• The preliminary SFN-RODS© required item reduction to achieve Rasch model fit, resulting in a 32-item SFN-RODS©.
• The final 32-item SFN-RODS© demonstrated acceptable reliability and validity, meeting Rasch requirements.
• The 13-item SFN-SIQ© was successfully transformed into an interval-level Rasch-built measure.

Conclusions:

• The 32-item SFN-RODS© is a disease-specific interval measure for assessing activity limitations and participation restrictions in SFN.
• The 13-item SFN-SIQ© is now a validated interval measure for SFN symptoms.
• These scales are recommended for use in future clinical interventional trials for SFN.