Moreover, CD activity markers, such as C-reactive protein, erythrocyte sedimentation rate, blood albumin level, fecal calprotectin, leucine-rich a2-glycoprotein, Crohn’s Disease Activity Index (CDAI), and the simple endoscopic score for CD (SES-CD), as the endoscopic scores using CS are generally used; however, sometimes they may not accurately reflect the activity of CD (e.g., the development of infection, the risk of underestimating lesions in the proximal small intestine) [54]. Here, CRP is linked to infection.