Background: Removal of colorectal neoplastic polyps can reduce the incidence of colorectal cancers. It is important to distinguish neoplastic from nonneoplastic polyps. We compared the ability of a trainee and an experienced endoscopist in distinguishing between neoplastic polyps and nonneoplastic polyps by conventional white-light, magnifying narrow-band imaging (NBI), and magnifying chromoendoscopy. Materials and methods: One hundred and sixty-three small colorectal polyps from 104 patients were studied. All polyps were diagnosed by trainees and experienced endoscopists using conventional white-light, magnifying NBI, and magnifying chromoendoscopy. The kappa values of interobserver agreement between trainees and experienced endoscopists were evaluated before this study. Sensitivity, specificity, and diagnostic accuracy were assessed by reference to histopathology. The first 50 polyps were diagnosed by the trainee as the first stage and the rest 113 polyps were diagnosed as the second stage. Results: Magnifying NBI and magnifying chromoendoscopy were significant better than conventional white-light by the experienced endoscopist (diagnostic accuracy: NBI 85.3%, chromoendoscopy 87.7%, conventional view 74.8%). No significant differences were found for the trainee. The kappa values (0.77∼0.85) were good for each endoscopic modality for the experienced endoscopist. However, only NBI and chromoendoscopy had acceptable kappa values (0.40∼0.48) for the trainee. The trainee improved diagnostic accuracy in the second stage, but not yielded the level of the experienced endoscopist. Conclusion: Magnifying NBI and magnifying chromoendoscopy had a better interobserver agreement than conventional white-light among trainees and experienced endoscopists. The trainee needs learning time to improve diagnostic ability, even using a new modality such as magnifying NBI.
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