Pathologist Experience and Concordance in the Diagnosis of Dysplasia in Long-standing Inflammatory Bowel Disease.

Surveillance colonoscopies focused to detect dysplasia are recommended to prevent colorectal cancer in patients with long-standing colonic inflammatory bowel disease (IBD). To date, histologic diagnosis and gradation of IBD-related dysplasia has been challenged by a high variability among pathologists. We aimed to analyze the observer characteristics that are correlated with concordance deviations in this diagnosis. Eight pathologists evaluated a set of 125 endoscopic biopsy samples with a representative distribution of nondysplastic and dysplastic lesions from long-standing IBD patients. Two rounds of diagnosis were carried out during a period of 18 months. The kappa test was applied to analyze concordance. Pathologists were grouped on the basis of their experience. A subanalysis was performed by eliminating the highly prevalent nondysplastic samples, as well as an analysis after observers' grouping. Overall interobserver agreement was good (kappa = 0.73), with an even higher pairwise value (kappa = 0.86) as well as the intraobserver agreement values (best kappa = 0.85). After eliminating the highly prevalent nondysplastic samples, the interobserver agreement was still moderate to good (best overall kappa= 0.50; best paired kappa = 0.72). Notable differences were seen between the pathologists with a high-volume and low-volume practice (best overall kappa = 0.61 and 0.41, respectively). The agreement in the diagnosis of dysplasia in IBD endoscopic biopsies may have been undervalued over time. This is the first study evaluating pathologists' diagnostic robustness in this field. The results suggest that examining a large volume of samples is the key factor to increase the consistency in the diagnosis and gradation of IBD-related dysplasia.