Development of a Bangla version of the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and the Bath Ankylosing Spondylitis Functional Index (BASFI)

AIM Development of a Bangla version of the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and the Bath Ankylosing Spondylitis Functional Index (BASFI). METHODS This biphasic observational study performed the translation and adaptation of the questionnaires carried out in 5 steps with pre-testing in 30 AS patients followed by the psychometric validation of the pre-final Bangla version utilizing content and construct validity in 115 AS patients. The reliability was examined through internal consistency and test-retest reliability involving 23 AS patients. RESULTS After pre-testing of the pre-final Bangla version of both indices, the psychometric validation found that the convergent validity of Bangla version of BASDAI showed strong correlation with C-reactive protein (r = .75) and the Maastricht Ankylosing Spondylitis Enthesitis (r = .64), and moderate correlation with erythrocyte sedimentation rate (r = .49). Again, the Bangla BASFI showed significant correlation with occiput-to-wall distance (OWD) (r = .50), mentum-to-sternum distance (MSD) (r = .50), chest expansion (CE) (r = -.40), finger-to-floor (FFD) (r = .55), number of swollen joints (r = .69), and number of enthesitis (r = .68). The divergent validity demonstrated weak correlations between BASDAI and OWD (r = .43), MSD (r = .34), CE (r = -.44), FFD (r = .47). The divergent validity of BASFI could not be assessed due to lack of a suitable comparing parameter. The instruments revealed acceptable internal consistency as Cronbach's alpha was 0.86 for BASDAI and 0.93 for BASFI. A 7-day test-retest reliability measured by the intraclass correlation coefficient were 0.80 (CI at 95% = 0.58-0.90) for BASDAI and 0.83 (CI at 95% = 95% 0.64-0.92) for BASFI respectively. CONCLUSIONS Bangla version of BASDAI and BASFI may be useful in disease activity and functional ability assessment in AS patients.