Optical diagnosis expanded to small polyps: Post-hoc analysis of diagnostic performance in a prospective multicenter study

Background: Optical diagnosis can replace histopathology of diminutive (1-5mm) polyps if surveillance intervals based on optical diagnosis of polyps have≥90% agreement with intervals based on polyp histology and if the negative predictive value (NPV) for predicting neoplastic histology in the rectosigmoid is≥90%. This study aims to assess whether small (6-9mm) polyps can be included in optical diagnosis strategies. Method: This is a post-hoc analysis of a prospective multicenter study in which 27 endoscopists, all performing endoscopies for the Dutch screening program, were trained in optical diagnosis. For 1 year, endoscopists recorded the predicted histology for all lesions detected using narrow-band imaging during 3144 consecutive colonoscopies after a positive fecal immunochemical test, along with confidence levels. Surveillance interval agreement and NPV were calculated for high confidence predictions for polyps of 1-9mm and compared with histopathology. Surveillance interval agreement was calculated using the European Society of Gastrointestinal Endoscopy surveillance guideline. Results: Surveillance interval agreement was 95.4% (confidence interval [CI] 94.2%-96.4%), and NPV for predicting neoplastic histology in the rectosigmoid 90.0% (CI 87.3%-92.2%). The reduction in histology (45.9% vs. 30.5%) and the proportion of patients who could have received direct surveillance advice (15.6% vs. 7.3%) was higher when small polyps were included (P <0.001). T1 cancer was found in seven small polyps (0.33%), five of which would have been discarded without histopathology. Conclusion: Including small polyps in the optical diagnosis strategy improves its efficacy while maintaining performance thresholds. However, there is a small risk of missing T1 cancers when small polyps are included in the optical diagnosis strategy.