Gastroesophageal reflux disease (GERD) is currently defined as "a condition which develops when the reflux of stomach contents causes troublesome symptoms and/or complications". Doctors often diagnose and treat GERD based on symptoms of heartburn and regurgitation. In recent years, the prevalence of partial or non-response to Proton Pump Inhibitors (PPI) has increased resulting in diagnostic testing with esophagogastroduodenoscopy (EGD) or ambulatory pH monitoring. Most patients do not have endoscopic evidence for reflux. Thus, in this group pH monitoring has emerged as an important physiologic test to determine the degree of esophageal acid exposure and to assess the association between patients' persistent symptoms and acid reflux events. The aims of this study are to assess the sensitivity and specificity of symptom associated indices and determine the best parameter for predicting GERD from a list of conventional pH measurement findings.

Inclusion Criteria:

• Male and female subjects ages 18 or older
• Presenting to the Vanderbilt GI outpatient clinic with symptoms of GERD
• Undergoing upper endoscopy and wireless pH monitoring (standard of care)
• Erosive disease: presence of esophageal mucosal injuries documented
• Non-erosive disease: normal esophagogastroduodenoscopy (EGD) with symptoms
• Control group: normal subjects without symptoms of GERD

Exclusion Criteria:

• Anti-reflux therapy within 7 days prior to the pH study
• Previous neck, esophagus, or stomach surgery
• Major motility disorders
• Previous neck, esophagus, or stomach cancer or radiations

Adult subjects presenting to Vanderbilt University Medical Center Gastroenterology outpatient clinic with symptoms consistent with gastroesophageal reflux disease (GERD)