Longitudinal Oral Microbiome Sampling for BE

Inclusion Criteria: * Scheduled for an upper endoscopy or had upper endoscopy within past three years * Eighteen years of age or older * Capable of producing a saliva sample * Able to give informed consent * For BE patients only: Endoscopic evidence of Barrett's esophagus (at least 1 cm maximal BE length; i.e. Prague classification: any C, M≥1), and intestinal metaplasia present on esophageal biopsies Exclusion Criteria: * History of head and neck cancer or esophageal squamous cell or gastric cancer * History of esophageal or gastric surgery * Scheduled to undergo colonoscopy on the day of initial saliva collection * Scheduled only for Endoscopic retrograde cholangiopancreatography (ERCP) or Endoscopy ultrasound (EUS) without accompanying standard upper endoscopy on the day of initial saliva collection * For BE patients only: History of prior endoscopic therapy for BE except a history of prior Endoscopic mucosal resection (EMR) of focal lesions without subsequent ablative therapy is permitted