Cutaneous Vasculitis in a Patient with Crohn's Disease Treated with Adalimumab.

Reply: We thank you for your interest in our article and for the comments in your correspondence. We agree that red cell distribution width (RDW) has been shown to correlate with disease activity in both ulcerative colitis and Crohn’s disease.1 However, our review’s main focus was on more specific, novel biomarkers of inflammatory bowel disease, and RDW is not a new test. As you state that RDW has the advantage of being a relatively noninvasive test, and the one which is cost effective; however, it has the same limitations as markers such as C reactive protein (CRP) and erythrocyte sedimentation rate (ESR), in view of its nonspecificity, and has been shown to correlate with disease activity in a number of conditions, including heart disease, chronic obstructive pulmonary disease, rheumatoid arthritis, and coeliac disease.2–5 In addition, it is affected by iron deficiency, and so this may result in misevaluation of results as iron deficiency is common in inflammatory bowel disease.6 Revisiting the use of established biomarkers does however have a place in the area of disease biomarker use, and our group has recently shown that noninvasively collected colorectal mucous, a previously underused sample medium, may enhance the utility of established markers.7 We reviewed briefly the use of other nonspecific markers including CRP and ESR as these are routinely used in clinical practice to aid in the evaluation of inflammatory bowel disease activity, whereas RDW currently is not.