Red cell distribution width as a marker of activity in inflammatory bowel disease: a narrative review

Red blood cell distribution width is a parameter measured automatically in every complete blood count that actually reflects the degree of anisocytosis of the red blood cell population. It is a cost-effective tool used in everyday clinical practice along with other parameters to define and narrow the cause of anemia. In a series of pathologic entities, such as cardiovascular diseases, autoimmune diseases, malignancy, chronic renal diseases and chronic respiratory diseases, where inflammation and oxidative stress comprise the major pathophysiologic insults, red cell distribution width behaves as a significant and competent marker able to predict and assess disease activity and severity. A number of clinical studies based on these observations have aimed to evaluate its potential utility as an index of activity in inflammatory bowel disease. In this narrative review we present data from the international literature regarding its ability to express disease activity and we look into its relation with clinical, laboratory and endoscopic indices used to identify active disease. According to the results of published clinical trials, red cell distribution width is considerably correlated with disease activity and might serve as an index to differentiate Crohn's disease from ulcerative colitis.