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

Objective. Behcet's disease (BD) is a rare multisystem disorder characteriz ed by vasculitis. At present, there are no laboratory markers that correlat e well with the clinical activity in ED. This has led to the development of an instrument (BD Current Activity Form) to measure activity. Scoring is b ased on the history of new clinical features present over the preceding 4 w eeks prior to assessment. Standardized questions were developed for all par ts of the form. The face validity of the proforma was determined following worldwide collaboration with physicians and ophthalmologists managing patie nts with ED. The aim of this study was to evaluate the interobserver reliab ility of this form. Methods. Nineteen patients fulfilling the International Study Group criteri a for BD were randomly allocated, questioned and examined independently on the same day by five physicians experienced in ED. Results. There was good agreement between the physicians' rating of oral [i ntraclass correlation coefficient (ICC) = 0.87] and genital (ICC = 0.95) ul ceration, skin involvement (ICC = 0.62 for pustules and ICC = 0.66 for eryt hema 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 o f bloody diarrhoea (ICC = 0.28). There was significant bias in the rating o f 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 proform a. has a place in routine clinical monitoring of patients with ED, as well as assessing outcome in therapeutic trials.