Virtual scale endoscope vs snares for size measurement accuracy of smaller colorectal polyps: A randomized controlled trial

Background and aims: Accurate measurement of polyp size during colonoscopy is crucial for informing clinical decisions such as resection techniques and surveillance scheduling. This study aimed to compare polyp size measurement accuracy when using a virtual scale endoscope (VSE) or snare-based polyp size measurement. Methods: This randomized controlled trial enrolled 221 patients undergoing screening, surveillance or diagnostic outpatient colonoscopies. Study subjects were randomized to have detected polyps measured for size either using VSE or a snare of known size to estimate the size of each polyp during the colonoscopy. All polyps were measured for reference size directly after their removal from the colon using a digital caliper and before formalin fixation. Results: 93 polyps were included in the VSE group and 102 in the Snare group. VSE demonstrated significantly higher relative accuracy (80.0% [95% CI: 77.0-82.9]) compared to snare-based size estimation (66.4% [95% CI: 62.4-70.5]; p<0.0001). Misclassification rates were lower with VSE for polyps >2mm (13.1% vs. 39.3%) and >3mm (22.6% vs. 55.4%). For diminutive polyps, VSE better prevented misclassification of >5mm polyps as 1-5 mm (21.4% vs. 73.0%). VSE also outperformed snare in measuring within 10% of reference standard size (30.1% vs. 18.6%) and had lower rates of size underestimation (36.5% vs. 65.7%). Conclusions: Using VSE improves polyp size measurement accuracy during colonoscopy in comparison with snare-based size estimation. In clinical scenarios, VSE reduced misclassifications at clinically relevant size thresholds 2,3 and 5mm which is relevant for adequate choice of polypectomy techniques or when implementing resect and discard strategies.