Variation in polyp size estimation among endoscopists and impact on surveillance intervals

Background: Accurate estimation of polyp size is important because it is used to determine the surveillance interval after polypectomy. Objective: To evaluate the variation and accuracy in polyp size estimation among endoscopists and the impact on surveillance intervals after polypectomy. Design: Web-based survey. Participants: A total of 873 members of the American Society for Gastrointestinal Endoscopy. Interventions: Participants watched video recordings of 4 polypectomies and were asked to estimate the polyp sizes. Main Outcome Measurements: Proportion of participants with polyp size estimates within 20% of the correct measurement and the frequency of incorrect surveillance intervals based on inaccurate size estimates. Results: Polyp size estimates were within 20% of the correct value for 1362 (48%) of 2812 estimates (range 39%-59% for the 4 polyps). Polyp size was overestimated by >20% in 889 estimates (32%, range 15%-49%) and underestimated by >20% in 561 (20%, range 4%-46%) estimates. Incorrect surveillance intervals because of overestimation or underestimation occurred in 272 (10%) of the 2812 estimates (range 5%-14%). Participants in a private practice setting overestimated the size of 3 or of all 4 polyps by >20% more often than participants in an academic setting (difference = 7%; 95% confidence interval, 1%-11%). Limitations: Survey design with the use of video clips. Conclusion: Substantial overestimation and underestimation of polyp size occurs with visual estimation leading to incorrect surveillance intervals in 10% of cases. Our findings support routine use of measurement tools to improve polyp size estimates.