Combination Methotrexate and Infliximab

Inclusion Criteria: * Fulfilled the AS:meeting the modified New York criteria * Active disease despite NSAID treatment defined as: * Spinal inflammation ≧ 30 and a score of 30 on at least two of the other three domains * Back pain * Patient global assessment of disease activity * Physical function * Informed consent Exclusion Criteria: * Complete ankylosis of the spine * On sulphasalazine * Previous use of TNF inhibitors * Multiple use of NSAIDS * Prednisolone \> 10mg/day * Changes of NSAIDS or dose of prednisolone within 2 weeks of baseline * Little or no ability for self-care * Received intra-articular,intramuscular, or intravenous corticosteroids in the 4 weeks before screening * Infected joint prosthesis during the previous 5 years * Serious infections, such as hepatitis, pneumonia, pyelonephritis in the previous 3 months * Any chronic infectious disease such as renal infection, chest infection with bronchiectasis or sinusitis * Active tuberculosis requiring treatment within the previous 3 years * Opportunistic infections such as herpes zoster within the previous 2 months * Any evidence of active cytomegalovirus; active Pneumocystis carinii; or drug-resistant atypical mycobacterial infection * Known hypersensitivity to murine proteins * Current signs or symptoms of severe,progressive,or uncontrolled renal, hepatic, haematological, gastrointestinal, endocrine, pulmonary, cardiac, neurological, or cerebral disease * A history of lymphoproliferative disease including lymphoma or signs suggestive of disease, such as lymphadenopathy of unusual size or location (ie,lymph nodes in the posterior triangle or the neck, infraclavicular epitrochlear, or periaortic areas); splenomegaly; * Any known malignant disease except basal cell carcinoma currently or in the past 5 years. * A hemoglobin level \< 8.5 gm/dl, a white blood cell count \< 3.5 × 10\^9/liter, a platelet count \< 100 × 10\^9/liter, a serum creatinine level \> 150 µmol/l, serum transaminase levels 1.25 times the upper limit of normal, or alkaline phosphatase levels \> 2 times the upper limit of normal.