The Behcet's disease activity index

Area of Science:

• Rheumatology
• Clinical Immunology
• Epidemiology

Background:

• Behçet's disease (BD) is a complex systemic vasculitis requiring accurate disease activity assessment.
• International standardization of BD activity indices is crucial for research and clinical practice.

Purpose of the Study:

• To identify and validate a subset of clinical features for an international Behçet's disease activity index.
• To assess the suitability of a disease activity scale for cross-cultural and pooled data analysis.

Main Methods:

• Rasch analysis was applied to data from 524 Behçet's disease patients across five countries.
• 14 items from the Behçet's Disease Current Activity Form were evaluated for unidimensionality and hierarchy.
• Differential item functioning (DIF) was assessed to identify cross-cultural variations.

Main Results:

• A 14-item scale showed good fit to the Rasch model within individual countries (Turkey, Korea, UK).
• Pooled data analysis revealed poor fit and significant cross-cultural DIF in seven items.
• After removing DIF items, a 26-item scale demonstrated good fit to the Rasch model for pooled data.

Conclusions:

• A 14-item index is suitable for disease activity assessment within specific countries.
• Rasch analysis facilitates valid international comparisons and data pooling for Behçet's disease activity.
• The validated scale offers a quick and user-friendly tool for clinical and research settings.