Since there is no head-to-head studies comparing the anti-TNF agents in the treatment of AS patients there is no ranking for the prescription of anti-TNF agents. Mixed treatment comparisons (that is statistical model allowing the simultaneous multiple meta-analysis of different pair-wise comparisons) between infliximab, adalimumab and etanercept did not show a statistically significant difference. Indeed similar improvements in Bath ankylosing spondylitis activity index (BASDAI 50) scores and ASAS partial remission (between 45.2% to 51.0% BASDAI 50 and 22.1% to 22.4% for partial remission) have been reported in randomized controlled clinical trials.