Defining disease status in ankylosing spondylitis: validation and cross-cultural adaptation of the Arabic Bath Ankylosing Spondylitis Functional Index (BASFI), the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), and the Bath Ankylosing Spondylitis Global score (BASG)

The Bath Ankylosing Spondylitis Functional Index (BASFI), disease activity index (BASDAI), and Global assessment (BASG) are the most commonly used instruments to assess patients suffering from ankylosing spondylitis (AS). The aim of this study was to translate, adapt, and validate these instruments into the Arabic language. Seventy-three AS patients were included in this study. One question in the BASFI questionnaire was changed to suit the Arabic culture. Also, the VAS in the questionnaires was transformed to numerical rating scales from 0 to 10. After modification, translation, and retranslation of the questionnaires, it was administered and tested for internal consistency, reliability, and construct validity. Magnetic resonance imaging (MRI) of the spine and sacroiliac joints was carried out for 69 patients; scores for disease activity and chronicity were also assessed. The adapted and translated questionnaires demonstrated acceptable comprehensibility scores with a mean of 9.3. Intraclass correlation coefficients for reliability and internal consistency was 0.973 for BASG, whereas standardized alpha ranged between 0.807 and 0.976. The modified item 9 in the BASFI demonstrated a good correlate to the principal component (0.883). When validated, all three questionnaires showed a significant correlation with enthesitis, BAS-radiology index, MRI imaging scores for activity and chronicity, C-reactive protein (CRP), and morning stiffness duration. The Arabic version of the BASFI, BASDAI, and BASG, showed adequate reliability and validity in patients with AS. The measurement properties were comparable to versions in other languages indicating that the questionnaires can be used for evaluation of AS Arabic-speaking patients.