Endoscopic grading of gastric intestinal metaplasia using blue light imaging in a low-risk population: Multicenter cross-sectional validation study.

Background study aims: Detecting gastric intestinal metaplasia (GIM) with white light endoscopy (WLE) remains a challenge and virtual chromoendoscopy methods have been shown to increase accuracy. We aimed to externally validate the Endoscopic Grading of Gastric Intestinal Metaplasia (EGGIM) using blue light imaging (BLI). Methods: First, the reliability of BLI and the EGGIM score was evaluated through assessment of 90 images divided into three sets of 30. A multicenter cross-sectional study was conducted at two Italian centers involving 102 patients (510 biopsies). Both per-biopsy and per-patient analyses were performed to ascertain accuracy of BLI in detecting and staging GIM (vs. histology). Results: BLI significantly enhanced interobserver agreement of endoscopic diagnosis of GIM, with a Fleiss Kappa of 0.4 (95% confidence interval [CI] 0.3-0.5), compared to 0.2 (95% CI 0.2-0.3) with WLE. Concordance was particularly strong in applying the EGGIM score (weighted Kappa 0.7; 95% CI 0.5-0.9). BLI showed significant improvements in sensitivity over WLE, with an increase observed in both per-biopsy analysis (82%; 95%CI 73.7-89.0 vs. 50%;95% CI 40.6-60.3) and per-patient analysis (96%; 95% CI 84.5-99.4 vs. 68%;95% CI 52.4-81.4). The area under the curve of EGGIM in diagnosing OLGIM III/IV was 0.9 (95% CI 0.8-1.0), confirming EGGIM > 4 being the optimal threshold (sensitivity of 80%, specificity of 88%). Conclusions: Our study validates BLI integrated with the EGGIM system as an effective strategy, highlighting its precision in identifying advanced GIM stages. BLI's notable sensitivity enhances its use as a complementary tool to WLE, significantly improving gastric cancer risk assessment.