Development and preliminary validation of the Behçet's syndrome Overall Damage Index (BODI)

To develop and validate the evidence-based and consensus-based Behçet's Syndrome Overall Damage Index (BODI).

Starting from 120 literature-retrieved preliminary items, the BODI underwent multiple Delphi rounds with an international multidisciplinary panel consisting of rheumatologists, internists, ophthalmologists, neurologists, and patient delegates until consensus was reached on the final content. The BODI was validated in a cross-sectional multicentre cohort of 228 patients with Behçet's syndrome (BS) through the study of (a) correlation between BODI and Vasculitis Damage Index (VDI) and (b) correlation between BODI and disease activity measures (ie, Behçet's Disease Current Activity Form (BDCAF), Physician Global Assessment (PGA), Patient Global Assessment (PtGA)), c) content and face validity and (d) feasibility.

The final BODI consists of 4 overarching principles and 46 unweighted-items grouped into 9 organ domains. It showed good to excellent reliability, with a mean Cohen's k of 0.84 (95% CI 0.78 to 0.90) and a mean intra-class correlation coefficient of 0.88 (95% CI 0.80 to 0.95). Overall, 128 (56.1%) patients had a BODI score ≥1, with a median score of 1.0 (range 0-14). The BODI significantly correlated with the VDI (r=0.693, p<0.001), demonstrating to effectively measure damage (construct validity), but had greater sensitivity in identifying major organ damage and did not correlate with disease activity measures (ie, BDCAF: p=0.807, PGA: p=0.820, PtGA: p=0.794) discriminating damage from the major confounding factor. The instrument was deemed credible (face validity), complete (content validity) and feasible by an independent group of clinicians.

Pending further validation, the BODI may be used to assess organ damage in patients with BS in the context of observational and controlled trials.