ESR1 and inflammatory bowel disease: A systematic review and meta-analysis by Menees et al. to determine the efficacy of CRP, ESR, fecal calprotectin, and fecal lactoferrin in inflammatory bowel disease in patients with irritable bowel syndrome showed that CRP and calprotectin levels of 0.5 and 40 rule out IBD in IBS symptoms and improve diagnosis [20].