Usefulness of C-Reactive Protein as a Disease Activity Marker in Crohn’s Disease according to the Location of Disease

BACKGROUND/AIMS C-reactive protein (CRP) is a serologic activity marker in Crohn's disease (CD), but it may be less useful in evaluating CD activity in ileal CD patients. We aimed to investigate the usefulness of CRP as a disease activity marker in CD according to disease location. METHODS Korean CD patients in a single hospital were evaluated. Factors associated with elevated CRP concentration at the time of diagnosis of CD and the association between the physician's prediction regarding upcoming surgery and the sites of the lesions directly related to surgery were analyzed. RESULTS Of 435 CD patients, 25.7%, 6.9%, and 67.4% had ileal, colonic, and ileocolonic CD, respectively. Multivariate analysis revealed that an elevated erythrocyte sedimentation rate, reduced serum albumin, CD activity index (CDAI) >220, and ileocolonic/colonic location were associated with an elevated CRP level and that the CRP level was significantly correlated with the CDAI in all CD patients (γ=0.466, p<0.01). However, the correlation coefficient was dependent on the location, with values of 0.395, 0.456, and 0.527 in patients with an ileal, ileocolonic, and colonic disease location, respectively. Surgery for ileal lesions was less predictable than surgery for ileocolonic or colonic lesions during follow-up. CONCLUSIONS CRP is less useful as a disease activity marker in patients with ileal CD than those with ileocolonic or colonic CD.