LAUSR

BACKGROUND To date no scale has been validated to assess bubbles impairing bowel preparation. The use of different descriptions in randomized trials limit clinical interpretation. Therefore, our goal was to develop and determine reliability of a novel scale - the Colon Endoscopic Bubble Scale - CEBuS. METHODS Multicentre prospective observational study with two online evaluation phases (Phase 1 - evaluation by four expert endoscopists; Phase 2 - six expert and 13 non-expert) of 45 randomly distributed still colonoscopy images (15 per scale level). Observers assessed images twice with a 2-week interval both a) using the CEBuS (CEBuS-0 - no or minimal bubbles, covering <5% of the surface; CEBuS-1 - bubbles covering 5-50%; CEBuS-2 - bubbles covering >50%); and b) reporting the clinical action (do nothing; wash with water; wash with simethicone). RESULTS CEBuS provided high levels of agreement both in phase 1 (experts) and 2 (mix expert/non-expert) with intraobserver reliability - Kappa 0.82 (95%CI 0.75-0.88) vs. 0.86 (0.85-0.88) - and for interobserver agreement - ICC 0.83 (0.73-0.89) vs. 0.90 (0.86-0.94). Previous endoscopic experience had no influence on agreement comparing experts and non-experts intra- and interobserver reliability - Kappa 0.86 (0.80-0.91) vs. 0.87 (0.84-0.89) and - ICC 0.91 (0.87-0.94) vs. 0.90 (0.86-0.94), respectively. Interobserver agreement on clinical action was - ICC 0.63 (0.43-0.78) vs. 0.77 (0.68-0.84). Absolute agreement on clinical action per scale level was - CEBuS-0 85% (82-88), CEBuS-1 21% (16-26), CEBuS-2 74% (70-78). CONCLUSION The CEBuS proved to be a reliable instrument to standardise the evaluation of colonic bubbles during colonoscopy. Assessment in daily practice is warranted.