Although there are different means of approaching the estimation of the activity and impact that these diseases generate, the two most commonly used composite indices to assess disease activity are the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and the Ankylosing Spondylitis Disease Activity Score (ASDAS), the latter being a derivation of the former that incorporates objective parameters such as C-reactive protein (CRP) or the erythrocyte sedimentation rate (ESR) [2]. This evidence concerns the gene CRP and ankylosing spondylitis.