High Confidence Optical Diagnosis Of Small Polyps at Colonoscopy Versus Histopathology: Moving Towards a New Gold Standard?

Aims Histopathology is regarded as the gold standard for diagnosis of small colonic polyps. However, there is growing interest in optical diagnosis and implementation of a ‘resect and discard’ strategy. Our aim is to evaluate accuracy of histopathology reporting where a high confidence diminutive polyp optical diagnosis was made and to assess the impact of performing additional tissue section re-cuts, where there is a discrepancy. Methods Eight bowel cancer screening colonoscopists optically diagnosed 639 diminutive polyps during the period Feb-Nov 2020 in the early phase of a prospective feasibility study of optical diagnosis (DISCARD3). Each polyp diagnosis was evaluated by the colonoscopist as high or low confidence. All retrieved polyps were sent for histopathology. Discrepancy between high confidence optical diagnoses and histopathology were re-reported by a second pathologist blinded to the original optical and histological call. If discrepancy remained after re-review, the polyp was re-cut into deeper levels and a third blinded histopathology review performed. Results Of 639 diminutive polyps, 468 (73.2 %) were high confidence optical calls and 171 (26.8 %) were low confidence. High confidence optical diagnosis agreed with histopathology in 78.2 % (366/468) of cases and disagreed in 21.8 % (102/468). In cases of disagreement, the initial histopathology was reviewed and 7.8 % (8/102) were due to histopathology error of which 3.9 % (4/102) corrected on second review and 3.9 % (4/102) corrected with deeper levels.There were no polyp cancers and 1 case of high grade dysplasia. Conclusions Although the majority of errors in optical diagnosis were related to incorrect high confidence calls a significant number were due to histopathology error. Change in practice to routinely perform additional deeper levels (ie 6 levels instead of 3) for small polyps appears to reduce this error rate by ~50 %. Optical diagnosis errors may be reduced by increasing the threshold for assignment of high confidence. Citation: Ahmad A, Wilson A, Moorghen M et al. OP183 HIGH CONFIDENCE OPTICAL DIAGNOSIS OF SMALL POLYPS AT COLONOSCOPY VERSUS HISTOPATHOLOGY: MOVING TOWARDS A NEW GOLD STANDARD?. Endoscopy 2021; 53: S76. Publication History Publication Date: 19 March 2021 (online) © 2021. European Society of Gastrointestinal Endoscopy. All rights reserved. Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany