A reproducible grading scale for histological assessment of inflammation in ulcerative colitis

Background-Evaluation of histological activity in ulcerative colitis needs to be reproducible but has rarely been tested. This could be useful both cl inically and in clinical trials. Aim-To develop reproducible criteria which are valid in the assessment of a cute inflammation (activity) and chronicity, and to evaluate these features in an interobserver variability study. Methods-A six grade classification system for inflammation was developed wh ich could also be fine tuned within each grade. The grades were: 0, structu ral change only; 1, chronic inflammation; 2, lamina propria neutrophils; 3, neutrophils in epithelium; 4, crypt destruction; and 5, erosions or ulcers . Ninety nine haematoxylin-eosin sections from endoscopically inflamed and non-inflamed mucosa from patients with distal ulcerative colitis were asses sed in two separate readings by three pathologists independently and withou t knowledge of the clinical status. Interobserver agreement was compared pa irwise using kappa statistics. Results-Initially, kappa values between the observers were 0.20, 0.42, and 0.26, which are too low to be of value. Following development of a semiquan titative pictorial scale for each criterion, kappa values improved to 0.62, 0.70, and 0.59. For activity defined by neutrophils between epithelial cel ls, kappa values were 0.903, 1.000, and 0.907. Complete agreement was reach ed in 64% of samples of endoscopically normal and in 66% of endoscopically inflamed tissue. Neutrophils in epithelium correlated with the presence of crypt destruction and ulceration. Conclusion-A histological activity system was developed for ulcerative coli tis that showed good reproducibility and modest agreement with the endoscop ic grading system which it complemented. It has potential value both clinic ally and in clinical trials.