A histopathologic scoring system as a tool for standardized reporting of chronic (ileo)colitis and independent risk assessment for inflammatory bowel disease

Summary Pathologists regularly evaluate for the presence of chronic (ileo)colitis in lower gastrointestinal mucosal biopsies, for which a major differential diagnosis is inflammatory bowel disease. Although the histologic features of chronic (ileo)colitis are clearly defined, there is no standard, experimentally derived and validated terminology to document these findings in pathology reports and to convey the likelihood of inflammatory bowel disease in a compact, consistent style. This study had 2 retrospective and 1 prospective phases. In phase 1, we developed a histopathologic scoring system for chronic (ileo)colitis and measured the agreement in scoring between pathologists. In phase 2, we emulated the surgical pathology practice by scoring mucosal biopsies of 164 patients who had undergone lower gastrointestinal endoscopies for clinical suspicion of (ileo)colitis. The cases were matched to 6 different groups based on clinical diagnoses. In phase 3, we prospectively assessed accuracy and ease of application of the scoring system in our practice. The scoring system showed low interobserver variability (correlation coefficient, 0.94-0.96) and distinguished chronic (ileo)colitis from negative cases. In addition, it enabled us to provide probabilistic diagnostic statements based on total scores and their positive predictive values, conveying the likelihood of inflammatory bowel disease as low (