Box 2: BSR guidelines for the use of anti-TNF therapy in ankylosing spondylitis 1. Patients should satisfy the modified New York criteria for diagnosis of AS 2. Active AS:   - Bath Ankylosing Spondyitis Disease Activity Index (BASDAI) at least 4cm   - And spinal pain Visual Analog Scale (VAS) (last week) at least 4cm   - Both on 2 occasions at least 4 weeks apart without any change of treatment 3. Failure of conventional treatment with >2NSAIDs, at maximum tolerated dosage for 4 weeks 4. Exclusion: similar to guideline for RA 5. Withdrawal of treatment:   - Adverse effects or   - Inefficacy - failure to improve BASDAI by 50% or 2 units and/or for spinal pain VAS to reduce by at least 2 units after 3 months of treatment