Natee Faknak MD1,Rapat Pittayanon MD1, Kasenee Tiankanon MD1,Anapat Sanpavat MD2, Naruemon Klaikaew MD2, Rungsun Rerknimitr MD1

1Division of Gastroenterology, Department of Medicine, Faculty of Medicine, Chulalongkorn University and King Chulalongkorn Memorial Hospital, The Thai red Cross Society, Bangkok, Thailand, 2Department of pathology, Faculty of Medicine, Chulalongkorn University and King Chulalongkorn Memorial Hospital, The Thai Red Cross Society, Bangkok, Thailand

Background/Aims: According to the 2019 British Society of Gastroenterology guideline, patients with gastric intestinal metaplasia (GIM) should have at least 5 biopsies performed under the Sydney protocol to evaluate for the risk of extensive GIM.However, certain evidences showed that only narrow band imaging (NBI) guided biopsy may be adequate to diagnose extensive GIM. To date, there has been no direct comparison on the validities of these two protocols.

Methods: A cross-sectional study from a tertiary care center in Thailand performed during November 2019 to October 2020.Patients with histology proven of GIM were enrolled in the study. All patients underwent standard esophagogastroduodenoscopy (EGD) by gastroenterology trainees.The performing endoscopists took biopsy from either suspected GIM area (NBI-guided biopsy) or randomly to complete 5 areas of stomach (lesser and greater curvature side of antrum, Incisura, lesser curvature and greater curvature of the body) as per the Sydney protocol.The gold standard for GIM diagnosis was the pathology read by two gastrointestinal pathologists.

Results: Total of 95 patients were enrolled in the study and 50 (52.6%). Extensive GIM was diagnosed in 43 patients (45.3%). There were no differences in baseline characteristic, indication for endoscopy and Helicobacter pylori status between patients with extensive and non-extensive GIM. The sensitivity, specificity, positive predictive value, negative predictive value (NPV) and accuracy of NBI guided biopsy vs. the Sydney protocol were 88.4% vs.100%, 90.3% vs. 90.3%, 88.4% vs. 89.6%, 90.3% vs.100% and 89.5% vs.94.7%, respectively.The area under the curve of NBI guided biopsy for extensive GIM diagnosis was significantly lower than that of from the Sydney protocol (0.88 vs. 0.95, p-value <0.001).

Conclusion: Both NBI-guided biopsy alone and NBI-guided biopsy under Sydney protocol by non-NBI expert gastroenterologist provided NPV higher than 90% and passed the PIVI threshold. Only NBI guided biopsy that requires less number of specimens is enough to diagnose extensive GIM.

Keywords: Gastric intestinal metaplasia, Sydney protocol