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

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BACKGROUND: Optical diagnosis can replace histopathology of diminutive (1 - 5 mm) 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 - 9 mm) 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 - 9 mm 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.