A pH Probe, or impedance study, is a test to measure how much reflux of stomach contents goes up into the esophagus. To perform this test, typically a long thin tube is placed through thenose down into the esophagus. The tube then remains in place for about a day which can measure changes in pH throughout the day. You are to record each time there are symptoms of acid reflux. The study looks to see how often there is increased acidity in the esophagus and if it correlates with symptoms of reflux. Results should be interpreted by a physician experienced with these studies.
If endoscopy was performed off of any type of antacid medication and biopsies revealed high numbers of eosinophils, a negative impedance or pH probe study can rule out reflux disease as the cause of the findings within the esophagus. If the pH probe study showed no evidence of reflux but there is eosinophilic inflammation, then eosinophilic esophagitis may be the likely diagnosis.