Disease activity is monitored by internationally validated tools, namely BASDAI (Bath Ankylosing Spondylitis Activity Index) and ASDAS (Ankylosing Spondylitis Disease Activity Score), with the C-reactive protein (CRP) or ESR (erythrocyte sedimentation rate) variant, which assesses the current impact of SpA. The gene discussed is CRP; the disease is spondylitis.