The importance of diagnostic accuracy in colonic inflammatory bowel disease

Crohn's disease (CD) and ulcerative colitis (UC) may both affect the colon. However, in approximately 10-20% of these cases, it is impossible to distinguish between these two entities either clinically or histologically, and a diagnosis of indeterminate colitis (IC) is made. Correct diagnosis is important because surgical treatment and long-term prognosis differ for UC and CD. The purpose of this study was to determine the extent of interobserver agreement among board-certified pathologists and a specialist gastrointestinal (GI) pathologist regarding the histological diagnosis of colonic inflammatory bowel disease (IBD).

A total of 24 university medical center pathologists from eight institutions evaluated 84 colectomy specimens and 35 sets of biopsy specimens from 119 consecutive patients with colonic IBD. A specialist GI pathologist subsequently reviewed all cases without knowledge of clinical data and prior diagnosis.

The GI pathologist's diagnoses differed from the initial diagnoses in 45% of surgical specimens and 54% of biopsy specimens. Of 70 cases initially diagnosed as UC, 30 (43%) were changed to CD or IC, whereas 4 of 23 cases (17%) initially diagnosed as CD were changed to UC or IC. The kappa coefficient for the overall agreement of initial diagnoses with the specialist GI pathologist's diagnoses was -0.01 (p = 0.98).

There is significant interobserver variation in the histological diagnosis of colonic IBD. This may have a profound effect on clinical patient care and, especially, on the choice of operation. More accurate diagnostic criteria are needed to facilitate patient care and to optimize treatment outcome.