Inclusion Criteria:1.Fulfilled ASAS2009 criterioncriteria; 2.The duration of axial syptoms less than 2 years and in active status before treatment(BASDAI≥4）；3.HLA-B27 positive；4.Completed the Etanercept treatment of 12-24 weeks;5. Completed the clinical data and questionnaire rbefore and after of the treatment; 6. Assigend the ICF. Exclusion Criteria:1. Received other anti-TNF-αagents treatment; 2.Patients with other rheumatic disease which may influent gene test and efficacy, including RA, PsA, OA, SLE, etc. 3.Other possible influence factors , including articular cavity local injections of glucocorticoid prior 4 weeks before TNF alpha antagonists treatment;4. Incomplete data.