Exclusion criteria for controls:

• Patients with history of esophagectomy or mucosal ablation, gastric fundoplication or other gastric surgery, or known non-Barrett's esophageal pathology (e.g. eosinophilic esophagitis or achalasia) will be excluded.
• Patients with prior history of colon polyps or colon/esophageal/gastric/pancreatic carcinoma (unless had negative colonoscopy within 2 years to clear polyps).
• Control patients without endoscopic evidence of Barrett's will be frequency matched by age (± 5 years) and gender (similar distribution) to cases. To ensure similar age and gender distribution between cases and controls, monitoring of recruited cases and controls age and gender distribution will be performed every two weeks. Data on height, weight, smoking history, medications (NSAIDS, PPIs) and indications (as well as findings on endoscopy) for endoscopy will be abstracted from medical records. All participants will be >18 years of age and will provide informed consent.

Exclusion criteria for cases:

• Patients with history of esophagectomy or mucosal ablation, gastric fundoplication or other gastric surgery, or known non-Barrett's esophageal pathology (e.g. eosinophilic esophagitis or achalasia) will be excluded.
• Patients with prior history of colon polyps or colon/gastric/pancreatic carcinoma (unless had negative colonoscopy within 2 years to clear polyps).
• Patients with esophageal varices or esophagitis LA Grade B,C, or D