TNF and spondylitis: TNFα: tumor necrosis factor-alpha; NS: no statistical significance in univariate analysis; NI: the difference was statistically significant in univariate analysis, but was not included in the multivariate regression analysis; HLA-B27: human leukocyte antigen B27; PGA: patient global assessment; VAS: visual analog scale; BASFI: Bath Ankylosing Spondylitis Functional Index; BASDAI: Bath Ankylosing Spondylitis Disease Activity Index; ASDAS: Ankylosing Spondylitis Disease Activity Score; CRP: C-reactive protein; ESR: erythrocyte sedimentation rate.