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

Abstract

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.

Keywords: BASDAI; BASFI; psychometrics; reliability; validity.