Reflux esophagitis is defined as pH of esophagus to be less than:

A reflux episode is defined as esophageal pH drop below four. Esophageal pH monitoring is performed for 24 or 48 hours and at the end of recording, patients tracing is analyzed and the results are expressed using six standard components. Of these 6 parameters a pH score called composite pH Score or DeMeester Score measure of esophageal acid exposure DeMeester score > 14.72 indicates reflux. Components of 24-h Esophageal pH Monitoring (DeMeester scoring) Percent total time pH < 4 Percent Upright time pH < 4 Percent Supine time pH < 4 Number of reflux episodes Number of reflux episodes > 5 min Longest reflux episode (minutes)