Behçet's disease: evaluation of a new instrument to measure clinical activity.

OBJECTIVE: Behçet's disease (BD) is a rare multisystem disorder characterized by vasculitis. At present, there are no laboratory markers that correlate well with the clinical activity in BD. This has led to the development of an instrument (BD Current Activity Form) to measure activity. Scoring is based on the history of new clinical features present over the preceding 4 weeks prior to assessment. Standardized questions were developed for all parts of the form. The face validity of the proforma was determined following worldwide collaboration with physicians and ophthalmologists managing patients with BD. The aim of this study was to evaluate the interobserver reliability of this form. METHODS: Nineteen patients fulfilling the International Study Group criteria for BD were randomly allocated, questioned and examined independently on the same day by five physicians experienced in BD. RESULTS: There was good agreement between the physicians' rating of oral [intraclass correlation coefficient (ICC) = 0.87] and genital (ICC = 0.95) ulceration, skin involvement (ICC = 0.62 for pustules and ICC = 0.66 for erythema nodosum), arthritis (ICC = 0.62), headache (ICC = 0.80), large vessel (kappa = 0.53), nervous system (kappa = 0.61) and eye involvement (kappa = 0.77). There was poor agreement for the question relating to the presence of bloody diarrhoea (ICC = 0.28). There was significant bias in the rating of fatigue by one of the physicians (F = 5.2, P = 0.001). CONCLUSION: Overall, this instrument has good interobserver reliability for assessing general disease activity. We therefore suggest that this proforma has a place in routine clinical monitoring of patients with BD, as well as assessing outcome in therapeutic trials.