Patient-driven assessment of disease activity in Behçet's syndrome: cross-cultural adaptation, reliability and validity of the Turkish version of the Behçet's Syndrome Activity Score.

Objectives: The Behçet's Syndrome Activity Score (BSAS) is the first patient reported outcome measure developed to assess the global disease activity in patients with Behçet's syndrome (BS). We aimed to evaluate the reliability and validity of the Turkish version of BSAS for measuring disease activity in BS. We further investigated the performance of Routine Assessment of Patient Index Data (RAPID)3, a patient-reported index originally developed for rheumatoid arthritis, in BS patients.

Methods: Patients seen consecutively at a tertiary Rheumatology Centre were requested to complete BSAS and multidimensional health assessment questionnaire (MDHAQ). Besides, all attending physicians filled the Behçet's Disease Current Activity Form (BDCAF). Descriptive statistics and Pearson correlation coefficients were calculated accordingly for the reliability and validity assessments of BSAS.

Results: A total of 104 patients completed all three assessments. The test-retest reliability of BSAS has a good level (ICC=0.84, 95% CI [0.69-0.94]). The mean scores for BSAS, BDCAF and RAPID3 were 39±20.8, 3.2±1.4 and 9.2±5.6, respectively. BSAS was correlated with BDCAF moderately (r=0.587), while it was moderately correlated with RAPID3 (r=0.648). The correlation between the RAPID3 and BDCAF was moderate (r=0.403), but lower as compared to the correlations between the other instruments.

Conclusions: We found that the BSAS has modest correlation with BDCAF and is a reliable and valid patient reported measure of disease activity that can be used to assess patients with BS. An outcome score composed of only patient-derived observations may have the additional advantage of being easier to use in a routine care setting. Demonstration of a moderate level of correlation between RAPID3 and BDCAF (close to the level of weak relationship), suggests that RAPID3 likely needs more investigations before recommending its use in BS.