BACKGROUND: Research has been reported that serum soluble CD146 (sCD146) expression was improved on the surface of endothelial cells and activated T cells by the stimulation of inflammatory factor. Therefore, it predicts that CD146 may participate in inflammatory reaction of tissue.OBJECTIVE: To investigate the expression and clinical significance of serum sCD146 in peripheral blood from patients with ankylosing spondylitis.METHODS: A total of 62 patients with ankylosing spondylitis were selected from the Sixth People's Hospital AffiUated to Shanghai Jiao Tong University. All patients were divided into two groups: active group (n=46) and inactive group (n=16); while, 20 healthy subjects were selected as the control group. Indicators including Bath Ankylosing SpondyUtis Disease ActivityIndex (BASDAI),Bath Ankylosing Spondylitis Functional Index (BASFI), patient's global assessment (PGA), night pain, visual analogue scale (VAS),morning stiffness time, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) were measured in all patients. The serum concentration of sCD146 from 62 patients with ankylosing spondlitis and 20 healthy controls was measured by enzyme-linked immunosorbent assay. Westergren method was used to measure ESR and immunoturbidimetry for CRP. Clinical data of the patients were collected as well.RESULTS AND CONCLUSION: sCD146 levels of patients with ankylosing spondlitis were significantly higher than normal control group (P ＜ 0.05). The sCD146 expression in the active group was significantly higher than inactive and normal control groups (P ＜0.05). Positive correlations were observed between sCD146 and BASDAI index of patients with ankylosing spondlitis (P ＜ 0.05).The sCD146 levels of ankylosing spondUtis patients with peripheral joint involvement were significantly higher than the patients with axial involvement alone or the normal controls (P ＜ 0.05).The expression level of sCD146 in peripheral blood was positively correlated with disease activities of patients with ankylosing spondlitis. It may play important roles in the pathogenesis in ankylosing spondlitis.