The Gastroscopy RAte of Cleanliness Evaluation (GRACE) Scale: an international reliability and validation study

Background and study aims: mucosal visualization during upper gastrointestinal (UGI) endoscopy can be impaired by the presence of foam, bubbles, and mucus. Some UGI endoscopy visibility scales were proposed but without a multicenter validation. This study aimed to develop and validate the Gastroscopy RAte of Cleanliness Evaluation (GRACE) scale. Patients and methods: a multicenter international cross-sectional study was conducted. The GRACE scale is based on a score from 0-worst to 3-excellent of esophagus, stomach, and duodenum, for a total ranging from 0 to 9. In the first phase, four expert endoscopists evaluated 60 selected images twice with a two-week interval; in the second phase, the same 60 images were scored twice by one expert and one non-expert endoscopist from 27 different Endoscopy Departments worldwide. For reproducibility assessment and clinical validation, a real-time scale application was performed on consecutive patients undergoing gastroscopy in each center. Results: in the internal validation, the interobserver agreement was 0.81 (95%CI[0.73-0.87]) and 0.80 (95%CI[0.72-0.86]), with a reliability of 0.73 (95%CI[0.63-0.82]) and 0.72 (95%CI[0.63-0.81]), in the two rounds, respectively. In the external validation, the overall interobserver agreement was 0.85 (95%CI[0.82-0.88]) with a reliability of 0.79 (95%CI[0.73-0.84]). In the real-time evaluation phase, the overall percentage of correct classifications was 0.80 (95%CI[0.77-0.82]). Conclusions: the GRACE scale showed good interobserver agreement and reliability and good validity. The spread of this scale could enhance the quality and standardize the cleanliness of the mucosa assessment during UGI endoscopy, pushing endoscopists to obtain excellent visibility and reducing the risk of missing lesions.