Inter-observer agreement on histological diagnosis of colorectal polyps: the APACC study

Introduction - Adenomas are considered as precursors of colorectal adenocarcinomas. After polypectomy, surveillance depends on the histological analysis of the excised polyps. The aim of the study was to evaluate the reproducibility of the histological diagnosis Performed by pathologists from participating centers in the APACC study. Their interpretations were compared to those of the study's consensual diagnosis performed by two reference pathologists. Methods - The agreement proportion and the concordance coefficient (kappa) were estimated for 326 polyps obtained from the first 748 patients included. Results - A concordant diagnosis for the adenomatous nature was shown for 246 of the 255 adenomas (96%). The diagnosis of both the histological type and the degree of dysplasia was concordant for only 92 of the 255 adenomas (36%). Kappa values were 0.67 for the adenomatous nature, 0.46 for the histological types, and 0.26 for the degree of dysplasia. Conclusion - A high degree of agreement was obtained for the diagnosis of the adenomatous nature. By contrast, high variations were observed for the interpretations of the histological type and the degree of dysplasia.