Introduction The LST classification and Paris classification systems are internationally used to describe polyp morphology. Differences between Japanese and Western endoscopists in the use of classification systems, have been observed but never studied formally. We aimed to evaluate the inter-observer agreement of LST classification amongst Western and Japanese expert endoscopists.
Method A total of 40 endoscopic video clips depicting LSTs (10% malignant) were assessed by 6 expert endoscopists; 3 from Japan and 3 from the Europe. Assessments included LST classification (LST-G homogeneous, LST-G mixed, LST-NG flat, LST-NG pseudodepressed), Paris classification, invasiveness, treatment suggestion and mean size of lesion. We calculated the interobserver agreement with weighted kappa and Chi square.
Results Japanese endoscopists diagnosed more lesions as LST-G than Western (62.7 vs. 45.4%), Western diagnosed more LST-NG than Japanese (54.6 vs. 37.3%; p=0.007). Lesions were deemed invasive by 18.8% and 11.7% Western and Japanese endoscopists respectively (p=0.088). Interobserver agreement of the LST classification was good with a weighted Kappa of 0.61 (CI 95% 0.43–0.78) for Japanese endoscopists, and moderate at 0.45 (CI 95% 0.27–0.64) for Western endoscopists. Difference in concordance between the two cohorts was not significant (p=0.22). When only two categories were considered (LST-G vs NG), agreement was very good for Japanese (weighted Kappa of 0.81; 95% CI 0.65–0.97) and good for Western endoscopists (0.65; 95% CI 0.46–0.85). Difference in concordance was not statistically significant (p=0.22). Piecemeal Endoscopic Resection was suggested in 34.7% cases by Western endoscopists, but none by Japanese endoscopists, whereas Endoscopic Submucosal Dissection was recommended in 50.4% and 16.1% cases by Japanese and Western endoscopists respectively (p<0.0001).
Conclusion Although there was significant differences in the subtypes of LST diagnosed, overall there was no significant difference between Japanese and Western endoscopists. The discordance in recommendations for treatment, ESD Vs EMR could be due to the differences in endoscopic skills and practice.
Disclosure of Interest None Declared
- Laterally spreading-type lesions (LST)