Similarly, AS patients show an increased level of serum amyloid.[20,21] Amyloid has been known as a useful indicator of disease activity, and it has shown a significant relationship with the markers (Bath Ankylosing Spondylitis Disease Activity Index score, erythrocyte sedimentation rate, and C-reactive protein) in AS.[20,21] The fourth hypothesis is related to the long-term persistent decline of physical activity in those with AS. Here, CRP is linked to ankylosing spondylitis.