Roel Bogie

Chapter 2

Abstract Objective

Correct endoscopic classification of Laterally Spreading Tumors (LSTs) in the colon and rectum is a prerequisite in order to predict the risk of containing submucosal invasion and to determine the optimal therapeutic plan. We examined the interobserver agreement (IOA) for classification of LSTs among international experts, and among fellows before and after training. Design We developed an educational web-based system to classify the aspect of LSTs using the endoscopic Kudo classification of LSTs. We used a case-based collection of LSTs with high-definition white-light endoscopy images and chromoendoscopy images. We calculated the IOA using Fleiss kappa coefficients, Gwet’s coefficients and the mean proportion of pairwise agreement. Results A total of 72 cases were assessed by 14 experts and 21 fellow raters. Overall, there is substantial IOA (Gwet’s AC1) for Kudo classification of LSTs (0.62, 95% CI: 0.55 – 0.69) and their categorization into granular vs non-granular subtype (0.75, 95% CI: 0.66 – 0.83) among experts. The IOA (Fleiss kappa) varies by endoscopic subtype: 0.76 (95% CI: 0.73 – 0.78) for LST-G-NM, 0.56 (95% CI: 0.53 – 0.58) for LST-G-H, 0.55 (95% CI: 0.52 – 0.57) for LST-NG-FE and 0.53 (95% CI: 0.50 – 0.55) for LST NG-PD. Training significantly improved the IOA for Kudo classification of LSTs among fellows (Gwet’s AC1 [95% CI]: 0.43 [0.37-0.50] before vs 0.59 [0.53-0.65] after, P <0.001). Conclusion Our study validates the Kudo endoscopic classification of LSTs. Substantial IOA was found for classification of LSTs among international experts and training significantly improved the IOA among fellows.

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