Eosinophilic Esophagitis Does Not Show Up on Routine Laboratory Tests
No, eosinophilic esophagitis (EoE) cannot be reliably detected through routine laboratory work—endoscopy with esophageal biopsy remains the only reliable diagnostic test. 1
Why Blood Tests Are Inadequate
Peripheral blood eosinophils are not diagnostic for EoE because the disease is primarily a local mucosal immune reaction (IgG4-mediated) confined to the esophageal tissue. 1
Only 10-50% of patients with EoE have elevated peripheral blood eosinophil counts, and when present, these elevations are typically modest (approximately 2-fold increases). 2
Even when peripheral eosinophilia exists, it is non-specific and cannot distinguish EoE from other eosinophilic disorders or allergic conditions. 2
It is very unlikely that a blood test will ever be an accurate diagnostic marker due to the pathophysiology of EoE as a localized tissue-based immune response. 1
The Gold Standard: Endoscopic Biopsy
Endoscopy with esophageal biopsy is the only reliable diagnostic test for EoE. 1, 3
Biopsy Requirements:
- 2-4 mucosal biopsy specimens from both proximal and distal esophagus should be obtained. 1
- Diagnostic sensitivity increases with more biopsies: 84% with 2 specimens, 97% with 3 specimens, and 100% with 6 specimens. 1
- Biopsies must be taken even if the esophagus appears normal endoscopically, as approximately 10% of patients with histologically confirmed EoE have normal-appearing mucosa. 1, 4
Diagnostic Criteria:
- ≥15 eosinophils per high-power field (0.3 mm²) on esophageal biopsy 3, 2
- Symptoms of esophageal dysfunction (dysphagia, food impaction, chest pain, heartburn) 3
- Exclusion of other causes of esophageal eosinophilia 3
Common Pitfalls to Avoid
Do not rely on endoscopic appearance alone: Only 38% of patients with endoscopic features suggestive of EoE are confirmed on biopsy, while 9.8% with normal endoscopy have histologic EoE. 3
Do not skip biopsies in patients on PPI therapy: Proton pump inhibitors may affect biopsy results, and patients on PPIs with normal biopsies cannot be definitively ruled out for EoE. 3
Do not assume typical allergy tests will help with diagnosis: Standard IgE-mediated allergy testing is not effective because EoE involves a non-IgE mediated allergic reaction. 5
Emerging Non-Invasive Methods (Not Yet Ready for Clinical Use)
Research is underway on alternative diagnostic methods including the Cytosponge, string tests, and blood messenger RNA levels of specific eosinophil markers (CD101 and CD274), but these are not yet validated or recommended for clinical practice. 1, 6