Serum C-reactive protein (CRP) is an acute-phase reactant produced by the liver that goes up with inflammation seen in a subset of patients with CD. It has a short half-life of 19 hours. Because of its short half-life, serum concentrations decrease quickly, making CRP a useful marker to detect and monitor inflammation (see later section) ( 34,35 ). Erythrocyte sedimentation rate is also a nonspecific measure of inflammation that may be elevated in patients with Crohn’s disease. Erythrocyte sedimentation rate may be useful in an individual patient but does not discriminate IBD patients from those with irritable bowel syndrome or healthy controls ( 36 ). Up to 40% of IBD patients with mild inflammation may have a normal CRP and erythrocyte sedimentation rate that may limit the usefulness of these markers in monitoring some patients ( 37 ).