LETTER TO THE EDITOR

RDW Can Be a Useful Additional Marker in Diagnosing Crohn’sDisease and Ulcerative Colitis

Tamas Molnar Æ Klaudia Farkas Æ Zoltan Szepes Æ Ferenc Nagy ÆTibor Nyari Æ Tibor Wittmann

Published online: 16 July 2008

� Springer Science+Business Media, LLC 2008

To the Editor

Clarke et al. [1] recently published a study on the potential

role of red blood cell distribution width (RDW) as a marker

for differentiating Crohn’s disease (CD) from ulcerative

colitis (UC). The authors examined the initial computer-

based data of their newly diagnosed patients and found a

slight, but statistically significant difference in favor of CD.

They conclude that RDW may prove to be a clinically

effective marker for differentiating CD from UC. However,

a number of questions are immediately raised: (1) because

RDW is highly dependent on iron level and blood loss, is

there any link between the activity status of inflammatory

bowel disease (IBD) and RDW level? Can the RDW dif-

ferentiate CD from UC in both the active state and in

remission? Does the change in RDW during the disease

course show any link with the laboratory activity markers

or clinical activity?

In view of these questions, we carried out a comple-

mentary study to retrospectively evaluate whether RDW

can facilitate clinicians in differentiating CD and UC both

in the active state and in remission and whether there is a

demonstrable correlation between RDW and the activity of

IBD.

We analyzed data on 176 IBD patients, including 92

patients with CD (57 females, 35 males; mean age

37.5 years, range 17–73 years) and 84 with UC (43

females, 41 males; mean age 44.4 years, range 16–81

years). The RDW values (reference range 11–14%), serum

iron level (reference range 6.6–26 lmol/l), C-reactive

protein level (CRP, reference range \5 mg/l), erythrocyte

sedimentation rate (ESR, reference range 1–20 mm/h) and

CD activity index (CDAI)/clinical activity index (CAI)

measured in both an active and an inactive disease period

of each patient were assessed. The active phase of the

diseases were defined as a CDAI [150/CAI [4 and/or a

CRP [5 mg/l and an ESR [20 mm/h. The data were

analyzed using the Pearson’s chi-square test, Fischer’s

exact test and one-sided Fischer’s exact test.

The RDW was increased in 53.2% of the patients with

inactive CD versus 36.8% of the patients with inactive

UC, representing a statistically significant difference

(average values 14.3 vs. 13.8; P = 0.05), while no sig-

nificant correlation was detected in the active period of

the diseases (14.7 vs. 14.4; P = 0.393). Increased RDW

correlated significantly with the low values of serum iron

level in CD patients and with serum iron level, CRP, ESR

in UC patients in remission—but not in CD patients with

the active form of the disease. Mean RDW was signifi-

cantly increased in the active form of both CD

(RDW [14%; P = 0.0019) and UC (RDW [14%;

P = 0.0263) and also in inactive CD cases (RDW [14%;

P = 0.0415) compared to the normal values of RDW

(RDW 11–14%).

Our results suggest that the RDW value may differ-

entiate between UC and CD in patients when these

diseases are in remission or inactive, but not when they

are active, which is clinically the more important time

for a reliable diagnostic tool. Since RDW reveals a sig-

nificant change with clinical activity, it could be a useful

T. Molnar (&) � K. Farkas � Z. Szepes � F. Nagy � T. Wittmann

1st Department of Medicine, University of Szeged,

Szeged, Hungary

e-mail: mot@in1st.szote.u-szeged.hu

T. Nyari

Department of Medical Informatics, University of Szeged,

Szeged, Hungary

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Dig Dis Sci (2008) 53:2828–2829

DOI 10.1007/s10620-008-0345-4

and inexpensive additional activity marker and also

facilitate the diagnosis of IBD. We agree with Clarke

et al. [1] that future evaluations will determine the exact

value of RDW alongside serologic markers in routine

diagnostic tests.

Reference

1. Clarke K, Sagunarthy R, Kansal S (2008) RDW as an additional

marker in inflammatory bowel disease/undifferentiated colitis. Dig

Dis Sci. Epub 8 Feb 2008

Dig Dis Sci (2008) 53:2828–2829 2829

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