A more precise prevalence of ID of approx. 45% in IBD, likely due to the selection of uniform ID threshold values from different studies (defined as serum ferritin < 30 μg/L or < 100 μg/L (if CRP is > 5 mg/L or > 10 mg/L) and TSAT < 16% or < 20%), was presented by the review Dignass et al. [5]. The gene discussed is CRP; the disease is inflammatory bowel disease.