Esophageal biopsies are essential for confirming the presence of EE, since there are no symptoms or blood tests that can accurately diagnose EE and rule out other possible disorders. Biopsies are taken during an upper endoscopy, and should be taken from multiple locations in the esophagus. The reason for multiple esophageal biopsies is that EE can be a patchy disease so one or two biopsies can miss this diagnosis. Furthermore, the biopsies should be taken while a person is on adequate anti-reflux medications to prevent acid reflux disease confusing the diagnosis. If anti-reflux medications were not being regularly taken, a pH or impedance study may be used to identify any underlying acid reflux.
Theses biopsies should be evaluated by a pathologist who has experience with eosinophilic gastrointestinal disorders. They need to be examined under a microscope to look for the presence of eosinophils which is the hallmark of this disease. The generally accepted criteria is that the PEAK eosinophil counts of more than 15 to 20 eosinophils seen on a single high powered microscopic field indicates that the diagnosis of eosinophilic esophagitis likely. In addition other microscopic findings may be seen to give clues to this diagnosis. Also eosinophilic inflammation of the upper esophagus with relative sparing of the lower esophagus may be more suggestive of EE vs GERD, since reflux disease is considered to be a continuum of inflammation, with signs of inflammation usually decreasing as you proceed higher up in the esophagus.