OBJECTIVE: Aim of this study is to compare the thiol/disulfide variables before treatment, at the 3 MATERIALS & METHODS: Consecutive patients with axial spondyloarthritis to whom biologic treatment was initiated in our clinic were enrolled upon consent. Demographics, clinical characteristics, laboratory parameters and treatment agents were collected. Disease activity scores and thiol-disulfide balance parameters were recorded at baseline and 3 RESULTS: In all patients, total thiol levels were significantly increased at 6 DISCUSSION & CONCLUSIONS: Our results demonstrated oxidative stress reducing effect of biologics in axSpA patients parallel to suppression of disease activity at 6