Development, validation, and responsiveness of a novel disease activity index for intestinal Behçet's disease.

Background: There is no disease activity index (DAI) currently available that can objectively assess the disease status of intestinal Behçet's disease (BD). The aim of this study was to develop a novel specific DAI for intestinal BD through a prospective study.

Methods: Items included in the index were produced and graded by experts in intestinal BD. Two separate cohorts of patients (weighting and validation cohorts) with intestinal BD were prospectively enrolled, and their clinical and laboratory data were collected. Through weighting items by multiple regression modeling, the DAI for intestinal BD (DAIBD) was derived using the weighting cohort and validated using the validation cohort. The index's responsiveness was evaluated using a longitudinal cohort derived from the weighting cohort at a follow-up visit 2-3 months later.

Results: A total of 110 patients with intestinal BD were enrolled in the weighting cohort. Eight of the 17 items selected by the experts accounted for 86.8% of the physician's global assessment (PGA) variance. The DAIBD calculated with gradations of weighted items correlated more strongly with PGA (r=0.850) than did the Crohn's disease activity index (CDAI) (r=0.649) in 50 patients of the validation cohort. Furthermore, quiescent, mild, moderate, and severe could be discriminated using the best cutoff scores. The DAIBD showed much higher responsiveness than did the CDAI (r=0.812 vs. 0.645, respectively) in 109 patients in the longitudinal cohort.

Conclusions: This novel DAIBD is an easy, valid, and responsive index to assess disease activity and can be useful to physicians who treat intestinal BD.