Differential diagnosis of colorectal polyps with narrow band imaging colonoscopy without magnification.

BACKGROUND/AIMS Narrow band imaging (NBI) endoscopy can be used for gross differentiation between the types of colonic polyps. This study was conducted as a retrospective study for estimation of the interobserver and intra-observer agreement of the pit pattern of the mucosal surface and the accuracy of histology prediction. METHODS A total of 159 patients underwent complete colonoscopy and 219 polyps examined by NBI endoscopy without magnification were assessed. Interobserver and intra-observer agreement were calculated by investigators in each group for determination of the surface pattern and prediction of histology based on the modified Kudo's classification using intraclass correlation coefficient. RESULTS Interobserver agreement for the surface pit pattern and prediction of polyp type was 0.84 and 0.73 in experienced endoscopists, and 0.86 and 0.62 in trainees, respectively. Intra-observer agreement for the surface pit patterns and prediction of polyp type was 0.81, 0.83, 0.85, 0.83, 0.56, 0.84, 0.51, 0.83, and 0.71; and 0.71, 0.70, 0.82, 0.54, 0.72, 0.37, 0.51, 0.34, and 0.30, respectively. The diagnostic accuracy for prediction of polyp type was 69.4% for experienced endoscopists and 72.9% for trainees. CONCLUSIONS NBI endoscopy without magnification showed fairly good inter and intra-observer agreement for the pit pattern of the mucosal surface and the accuracy of histology prediction; however, it had some limitation for differentiation of colon polyp histologic type. Training and experience with NBI is needed for improvement of accuracy.