Background: This study evaluated inter- and intraobserver agreement in the assessment of ulcerative colitis (UC) activity using 4 established indices and a newly designed Modified 6-point Activity Index.

Methods: In all, 279 endoscopic pictures of inflammatory lesions from 93 UC patients were displayed twice to 4 expert and 4 trainee endoscopists, at an interval of 1 month. Each picture was assessed for inflammatory changes using established indices (Matts, Schroeder [a.k.a. Mayo Score], Baron, and Blackstone) and our new Modified 6-point Activity Index. Weighted kappa statistics were used to estimate intra- and interobserver variation.

Results: The Matts and Schroeder indices gave a "good" degree of concordance for expert endoscopists in terms of inter- and intraobserver agreements (0.74-0.78); this was not so evident with the Baron and Blackstone indices (0.61-0.73). For trainee endoscopists, all scores for inter- and intraobserver weighted kappa values using established indices (0.41-0.51) were lower than for the experts. The degree of concordance using the Modified 6-point Activity Index was rated as "good" for inter- and intraobserver agreements for expert endoscopists (0.65 and 0.79), and as "moderate" for trainee endoscopists (0.54 and 0.64).

Conclusions: Accurate assessment of UC disease activity from endoscopic findings benefited from experience. For expert endoscopists, the Matts and Schroeder indices proved the most reliable of the 4 established indices. Current endoscopic technologies may be adequate for assessing UC activity, particularly if modified to permit a finer classification of disease severity based on 6 grades, as with our newly developed Modified 6-point Activity Index.