Evaluation of a German version of the Bath Ankylosing Spondylitis Functional Index (BASFI) and Dougados Functional Index (D-FI)

Objective: Transcultural adaption of the two most widely used and accepted functional indices in ankylosing spondylitis, the Bath Ankylosing Spondylit is Functional Index (BASFI) and Dougados Functional Index CD-FI). Methods: The instruments were translated and tested for internal consistenc y (Cronbach's coefficient alpha), test-retest reliability (intraclass corre lation coefficient, ICC), construct validity (testing for association with Schober's test, finger floor distance, occiput wall distance, frequency and duration of awakenings at night, and a visual analog scale pain), and resp onsiveness (standardized response mean, SRM). Results: The study sample consisted of 72 patients of a randomized, control led clinical trial receiving either Diclofenac or placebo. Visual assessmen t of distribution patterns revealed a ceiling effect of both instruments. B oth questionnaires had a high internal consistency (Cronbach alpha: 0.81 [B ASFI], 0.85 [D-FI] and a high test-retest reliability (ICC: 0.92 [BASFI], 0 .89 [D-FI]). The limited responsiveness to Diclofenac treatment (SRM: 0.46 [BASFI], 0.33 [D-FI]) may be related to the selected study sample. The BASF I was significantly correlated with all tested validation parameters. The D -FI was only significantly correlated with finger floor distance, occiput w all distance, and duration of awakenings at night. Conclusion: The transculturally adapted version of both functional indices are valid. reliable, and internally consistent. Because of psychometric adv antages, the BASFI may be preferred in clinical trial settings.