Reply to Cheng et al.

We express our gratitude to Cheng et al. for their keen interest and comments on our recent study in which we evaluated a virtual scale tool for endoscopic polyp size measurement [1] [2].

The authors mention that the classifying performance of the virtual scale was suboptimal and the mean error was largest for virtual scale measurements (using histopathological size as reference), which may indicate a certain variability in the virtual scale measurements. We agree that virtual scale measurement is not perfect as with interpretation of the virtual scale a certain degree of interobserver variability remains. However, conclusions regarding measurement variability cannot be drawn from mean errors as these only provide information regarding average “bias” and not variability (spread) of measurements. In addition, the debatable reliability of histopathological polyp size measurement should be considered when interpreting reported mean errors [2]. In terms of clinical relevance, it seems most important that (classifying) performance of the virtual scale was superior to that of the other methods.

User-friendliness was only assessed for the virtual scale because the virtual scale is the only tool specifically designed for polyp sizing. Visual inspection and positioning snares for polypectomy are routinely performed when detecting and removing polyps. Polyps were not measured using a biopsy forceps in our study as their routine use for polypectomy in daily practice is discouraged due to the high incomplete resection rate [3]. As such, structural use of forceps for polyp sizing would lead to unnecessary use of materials.

We agree that a real-world study would provide the most reliable insights into clinical feasibility of the virtual scale. However, we opted for a video-based approach to assess measurement variabilities as consecutive measurement of the same polyps by multiple endoscopists is logistically challenging and burdensome for patients. Regarding the proposed sensitivity analysis, we would like to emphasize that we did not completely exclude the unsuccessful measurements but mentioned these explicitly in our report. Furthermore, only 4/141 polyps (2.8%) were excluded because they could not be measured within the allotted time using the virtual scale.

To conclude, we agree that further studies are required to evaluate real-world feasibility. Notwithstanding, our results prove that the virtual scale may serve as a robust and potentially superior option for polyp sizing compared with other currently available options.

Publication History

Article published online:
28 January 2025

• References

• 1 Cheng Y, Ren X, Yi I. Is a virtual scale a better option for polyp size measurement?. Endoscopy 2024; 56: 173-174
• 2 van Bokhorst QNE, Houwen BBSL, Hazewinkel Y. et al. Polyp size measurement during colonoscopy using a virtual scale: variability and systematic differences. Endoscopy 2024; 56: 137-145
• 3 Ferlitsch M, Hassan C, Bisschops R. et al. Colorectal polypectomy and endoscopic mucosal resection: European Society of Gastrointestinal Endoscopy (ESGE) guideline – update 2024. Endoscopy 2024; 56: 516-545