Virtual Scale Function SCALE EYE: Variability and Systematic Differences (SCALE-EYE)

Polyp Size Measurement During Real-time Colonoscopy Using the Virtual Scale Function SCALE EYE: Variability and Systematic Differences

Size of colorectal polyps is important to decide on appropriate surveillance intervals and treatment modality, as well as carrying out optical diagnosis strategies. However, polyp size measurement is often prone to inter-observer variability. An easy and accurate tool to assist in polyp size measurement is required. Recently, a virtual scale function for size measurement during endoscopy (SCALE EYE), operating in real-time without the use of any additional devices, has been developed. The aim of this study is to assess whether use of the SCALE EYE for polyp size measurement can reduce inter-observer variability.

This study is designed as a single center prospective study. Polyp size measurements using SCALE EYE will be compared with several other polyp size measurement techniques: size measurements by endoscopists without a reference ('carpenters eye') , size measurements by endoscopists with an opened snare (of known size) as reference and size measurements by the pathologist during histopathological analysis. During screening colonoscopies, detected polyps (maximum of four per colonoscopy) will be measured using all three different colonoscopy measurement techniques. This will be done by experienced endoscopists (endoscopist accredited for colonoscopies within the national colorectal cancer screening program). Since endoscopists measure polyps in multiple ways, consecutive measurements of the same polyp will be biased. For this reason, all polyp size measurements will be recorded on video. The video recordings of the different measurements of all polyps will be presented to eight expert endoscopists and four to eight trainees (depending on availability) in a randomized order. The size estimations based on these video recordings will be used for further analysis. Histopathological analysis and size measurements of the resected polyps will be performed by pathologists with expertise in gastrointestinal pathology. Variability and systematic differences in polyp size measurement between different measurements methods will be assessed.

All patients within the study are included in the intervention arm: polyp detected within these patients will be measured according to the study protocol using four different methods.

The difference in residual variance (variability) between (1) polyp size measurement with SCALE EYE and (2) polyp size measurement using an opened snare (of known size) as reference.

The difference in residual variance (variability) between polyp size measurement with (1) the SCALE EYE functionality, (2) polyp size measurement without reference and (3) polyp size measurement during histopathological analysis.

The systematic difference in polyp size measurements between (1) the SCALE EYE functionality and the other measurement techniques: (2) polyp size measurement without reference, (3) polyp size measurement with an opened snare as a visual reference and (4) polyp size measurement during histopathological analysis.

Aforementioned parameters / outcomes (and primary study parameter) based on assessment by trainees (for other analyses assessment by experts will be used).

The accuracy of the SCALE EYE functionality for predicting the size of polyps. Accuracy is defined as the percentage of correctly predicted polyp sizes with the SCALE EYE functionality when polyp size measurement with an opened snare is considered as reference standard. Polyp size will be assigned as correctly predicted if the polyp size measurement with SCALE EYE lies within a 25% margin of error. The mean of the polyp size measurements by all experts endoscopists will be used for the comparison.

The accuracy of the SCALE EYE functionality for predicting polyp size for different polyp size categories (1-5 mm vs. 6-9 mm vs. >10 mm). Accuracy is defined as the percentage of correctly predicted polyp sizes with the SCALE EYE functionality when polyp size measurement with an opened snare is considered the reference standard. Polyp size will be assigned as correctly predicted if the polyp size measurement with SCALE EYE lies within a 25% margin of error. The mean of the polyp size measurements by all expert endoscopists will be used to assign the polyp size category.

Average time to manoeuver SCALE EYE during live endoscopy (i.e. time to perform measurement of one polyp).

Inclusion Criteria: Age >18 years Screening colonoscopy after positive fecal immunochemical test (FIT) within the Dutch colorectal cancer screening program Signed informed consent Exclusion Criteria: Diagnosis of inflammatory bowel disease, Lynch syndrome or (serrated) polyposis syndrome