AB0491 ELEVATED COMPLEMENT 3 INDICATES DISEASE ACTIVITY IN TAKAYASU ARTERITIS

Background: The disease activity evaluation of Takayasu arteritis (TA) is a critical issue for disease monitoring and treatment. But the previous markers such as Kerr score or ITAS 2010 are not convenient enough. Objectives: We aim to explore novel biomarkers to assess TA disease activity. Methods: This cross-sectional study was based on the East China TA (ECTA) cohort. Demographic characteristics, clinical features, laboratory and imaging results were collected. Complements and their combination with other biomarkers in identifying active disease (Kerr >= 2) group were analyzed. Internal and external validation were employed to confirm the accuracy and stability of the results. Results: 519 patients were enrolled, among which 406 cases (72.2%) were identified as active disease. Higher ESR, CRP, platelet, globulin, IgG, IL-6, complement 3 (C3), complement 4 (C4) and median haemolytic complement (CH50) levels were observed in the active disease group. Logistic regression analysis demonstrated that C3 levels [odds ratio [OR] (95%CI): 10.710(1.825 – 62.835), P = 0.009] and CRP [OR (95%CI): 1.041(1.009 – 1.073), P = 0.011] were independently associated with active disease. The cut-off of C3 to identify active TA was 1.085 g/L, with 69.9% sensitivity, 66.7% specificity. Combining the CRP (cut-off, 10.65g/L; sensitivity, 50.7%; specificity, 82.4%) and C3, the sensitivity and specificity to identify the active disease were 85.1% and 55.0% (parallel test), and 35.4% and 94.1% (serial test), respectively. C3 could significantly improve the diagnostic ability of CRP [net reclassification index: OR (95%CI): 1.728 (1.556–1.990), P = 0.000; integrated discrimination index: OR (95%CI): 0.328 (0.224–0.431), P = 0.000]. The accuracy of the 10-fold cross validation of combining CRP with C3 was over 75%, and the accuracy of the external validation with 53 TA cases was 72.73%. Conclusion: C3 could reflect the disease activity of TA, and combining CRP with C3 could significantly improve the disease activity evaluation in TA. References: [1]Ma J, Luo X, Wu Q, Chen Z, Kou L, Wang H. Circulation levels of acute phase proteins in patients with Takayasu arteritis. J Vasc Surg. 2010;51(3):700-6. Acknowledgments: This work was supported by the National Natural Science Foundation of China [NSFC 81771730 and 81601398]. Disclosure of Interests: : None declared