Upper GI Symptoms

The purpose of this prospective cohort study is to compare upper GI symptoms and endoscopy findings in Canada with Japan and Iran, and correlate this with the upper GI microbiome. The investigators plan to recruit 500 new patients referred for upper GI endoscopy in Canada (McMaster University) and 500 in Japan (Tohoku University Hospital) and 500 from Iran (Tehran University of Medical Sciences). Written consent will be obtained from all participants. Patients will complete three symptom questionnaires and a demographic one before endoscopy. Then saliva collection device will be applied for collecting saliva and microbiota from the oral cavity. Esophagogastroduodenoscopy (EGD) will be performed thereafter and brushing of the esophagus, stomach, and the duodenum will be done using a sterile sheathed brush (one for each site) to sample collect gut microbiota and gastric biopsies will be done for assessing H.pylori status. In addition, a group of these patients will undergo measurement of nitrate reductase activity (NRA) in their oral cavity. This will be done on twenty erosive gastro-esophageal reflux disease (GERD) patients, twenty non-erosive GERD patients, and twenty patients without any endoscopic or clinical GERD. This latter part of the study will be done at the Canadian and Iranian sites only. Bacterial community profiling of the 16S rRNA gene will be carried out using paired end reads of the V3 region. Triplicate amplifications will be pooled for 150 or 250 nt paired-end Illumina sequencing in the McMaster Genome Center. For specific substudies analysis of the mycome will also be carried out.