Serum levels of TNF-α have been shown to correlate with clinical activity indices such as the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and Ankylosing Spondylitis Disease Activity Score based on C-reactive protein (ASDAS-CRP), as well as with CRP and erythrocyte sedimentation rate (ESR) [10,11,12]. This evidence concerns the gene CRP and ankylosing spondylitis.