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.
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.