Non-Steroidal Anti-inflammatory Drugs in Axial Spondyloarthritis

Inclusion Criteria:

• A clinical diagnosis of ankylosing spondylitis (AS) by treating rheumatologists, or adiagnosis of axial spondyloarthritis (axSpA) with a pelvis MRI with significant bonemarrow edema on STIR sequences;

• Minimum of 18 years old;

• Are taking NSAIDs on a regular basis for AS or axSpA (defined as more than 20 days inthe past month) and willing to withhold medication for one week; or having activesymptoms that require initiation of NSAIDs;

• Concomitant anti-rheumatic drugs are allowed, if the dose has been stable for the pastthree months;

• Have active disease after initial washout period, defined by BASDAI >=4/10, or backpain numerical rating scale (NRS)>=4/10

Exclusion Criteria:

• Patients who have concurrent rheumatic diseases other than AS or axSpA;

• Patients who have oral corticosteroid in the past two weeks; patients who have acuteperipheral arthritis;

• Patients with a fibromyalgia score >= 13;

• Patient with extensive cardiac history, history of gastrointestinal bleeding thatrequired blood transfusion, chronic kidney diseases, abnormal liver function tests; orfemale patients who are pregnant. Use of low-dose of aspirin (<100mg daily) is allowed in the study.