Material and Method: The original BASDAI, BASFI, and BASG were translated to Thai language and re-translated back by professional translators. The translated questionnaires were subsequently modified by a panel of rheumatologists and small group of AS patients to suit the Thai culture. To assess the validity, scores from these instruments were validated against clinical signs and symptoms and inflammatory indices including arthritis and fatigue symptoms, occiput to wall distance, chest expansion, Schober’s test, finger to ground distance, erythrocyte sedimentation rate, and C-reactive protein. Reliability was tested by internal consistency.

Results: Thirty-eight patients were included in the present study. The BASDAI, BASFI, and BASG showed a significant correlation with arthritis and fatigue symptoms, finger to ground distance, erythrocyte sedimentation rate, and C-reactive protein. Internal consistency (Cronbach’s alpha) of BASDAI, BASFI, and BASG were 0.867, 0.915, and 0.315 respectively.

Conclusion: Thai version BASDAI, BASFI, and BAS-G showed good validity in patients with AS. There was a good internal consistency for BASDAI and BASFI. These questionnaires are feasible for application in clinical practice on Thai AS patients.

Keywords: Reliability, Validity, BASDAI, BASFI, BASG, Thai version