BRIEF REPORT Psychometric evaluation of the Moroccan version of the Bath Ankylosing Spondylitis Functional Index (BASFI) and Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) for use in patients with ankylosing spondylitis Samira Rostom & Karima Benbouaaza & Bouchra Amine & Rachid Bahiri & Yousra Ibn Yacoub & Sanae Ali Ou Alla & Redouane Abouqal & Najia Hajjaj-Hassouni Received: 12 June 2009 / Revised: 14 December 2009 / Accepted: 10 March 2010 / Published online: 10 April 2010 # Clinical Rheumatology 2010 Abstract The objectives of this study are to translate, adapt in the Moroccan cultural context, and validate in patients with ankylosing spondylitis (AS) the Bath Ankylosing Spondylitis Functional Index (BASFI) and Bath Ankylosing Spondylitis Disease Activity Index (BASDAI). The cross-cultural adap- tation of the BASFI and BASDAI was obtained in accordance with the guidelines for translation of the health status measures. Eighty-five patients with AS were included in the study. The test–retest reliability and the internal consistency were analyzed, and both questionnaires were assessed for external construct validity. Structural validity was analyzed with correlation matrix. Twenty-four-hour test–retest reliabil- ity was good: BASFI intraclass correlation coefficient (ICC)= 0.96 (confidence interval (CI) at 95%, 0.93–0.97), BASDAI ICC=0.93 (CI at 95%, 0.90–0.95). Cronbach’ s alpha was 0.90 for the BASFI and 0.86 for BASDAI. The construct validity of the instruments was evaluated. The BASFI showed a strong validity when correlating its results with Schober’ s test (r = -0.56), occipital wall distance (r =0.46), chest expansion (r = -0.46), BASDAI (r =0.54), Bath Ankylosing Spondylitis Metrology Index (r =0.70), Bath Ankylosing Spondylitis Global Score (BAS-G; r =0.58), Bath Ankylosing Spondylitis Radiology Index (r =0.61), and the radiological changes in sacroiliac joints (r =0.54). A good correlation was observed between the BASDAI and the spinal pain (r =0.53), the number of nocturnal awakenings (r =0.57), the morning stiffness (r =0.65), the enthesic index (r =0.47), the BAS-G (r =0.53), the BASFI (r =0.54), and the erythrocyte sedimentation rate (r =0.41; for all p <0.001). The correlation matrix showed an intermediate correlation between items. The Moroccan version of the BASFI and the BASDAI showed adequate reliability and validity. These instruments can be used in the clinical evaluation of Moroccan and Arabic-speaking patients with AS. Keywords Ankylosing spondylitis . Disease activity . Functional index . Moroccan version . the Bath Ankylosing Spondylitis Disease Activity Index . the Bath Ankylosing Spondylitis Functional Index Introduction Ankylosing spondylitis (AS) is a chronic inflammatory disease that can lead to a functional disability and deterioration of quality of life. The assessment of AS in different settings for disease control, symptom modifica- tion, and clinical record keeping is currently done through endpoints emphasizing disease activity and function. Currently, there are three instruments that are reliable, valid, and sensitive to change that have been recommended by the AS Assessment (ASAS) Working Group to measure such domains. Of these, the Bath Ankylosing Disease Activity Index (BASDAI) measures disease activity while the two others, the Bath Ankylosing Spondylitis Functional Index (BASFI) and the Dougados Functional Index, measure functioning [1–3]. They have been selected by S. Rostom (*) : K. Benbouaaza : B. Amine : R. Bahiri : Y. Ibn Yacoub : S. Ali Ou Alla : N. Hajjaj-Hassouni Department of Rheumatology, El Ayachi hospital, University Hospital, 11000 Sale, Morocco e-mail: rostomsamira2003@yahoo.fr R. Abouqal Laboratory of Biostatistics, Clinical Research and Epidemiology, Faculty of Medicine and Pharmacy, Rabat, Morocco Clin Rheumatol (2010) 29:781–788 DOI 10.1007/s10067-010-1431-5