Blood Tests in Eosinophilic Esophagitis: Diagnosis and Management
Blood tests are not useful for diagnosing or managing eosinophilic esophagitis (EoE), and endoscopy with esophageal biopsy remains the only reliable diagnostic test. 1
Why Blood Tests Are Not Recommended
It is very unlikely that a blood test will be an accurate diagnostic marker of EoE because of the pathophysiology of the condition as a local mucosal immune reactivity. 1 The disease is characterized by tissue-specific eosinophilic infiltration confined to the esophageal mucosa, which does not reliably correlate with systemic markers. 1
Peripheral Eosinophilia Has Poor Diagnostic Utility
- Peripheral blood eosinophilia occurs in only 10-50% of adults with EoE and 20-100% of children, and when present is usually only modestly elevated (2-fold). 2, 3, 4
- Normal blood eosinophil counts do not exclude EoE, making peripheral eosinophil measurement unreliable as a screening or diagnostic tool. 2, 3
- Tissue biopsy is the gold standard; peripheral eosinophil count alone is insufficient for diagnosis. 3
Investigational Biomarkers Are Not Ready for Clinical Use
While research into systemic biomarkers is ongoing—including blood messenger RNA levels of CD101 and CD274 expressing eosinophils—none are ready for clinical application. 1 These remain research priorities rather than established diagnostic tools. 1
The Gold Standard: Endoscopy with Biopsy
Endoscopy with esophageal biopsy remains the only reliable diagnostic test for EoE. 1 The diagnosis requires:
- Upper endoscopy with at least 6 biopsies: 2-3 from the proximal esophagus and 2-3 from the distal esophagus. 2, 3
- Histologic confirmation of ≥15 eosinophils per 0.3 mm² (high-power field) in esophageal tissue. 2, 3, 4
- Biopsies should be obtained even when the esophagus appears endoscopically normal, as 9.8-10% of patients with normal-appearing esophagus have histologic EoE. 1, 5, 6
Monitoring Disease Activity
Blood tests are equally unhelpful for monitoring treatment response or disease activity. 1 Management decisions require:
- Repeat endoscopy with biopsies if symptoms recur during treatment. 2, 3
- Histological remission is defined as <15 eosinophils per 0.3 mm², with deep remission as <5 eosinophils per 0.3 mm². 2, 3, 4
- Topical swallowed corticosteroids decrease blood eosinophil counts in 88% of patients, but this peripheral change does not reliably reflect mucosal disease activity and should not guide management. 2, 3
Common Pitfalls to Avoid
- Do not rely on peripheral eosinophil counts to diagnose or exclude EoE—tissue diagnosis is mandatory. 2, 3
- Do not use blood eosinophil levels to assess treatment response—repeat endoscopy with biopsy is required to document histologic remission. 2, 3
- Do not assume that normalizing peripheral eosinophilia indicates mucosal healing, as these parameters do not correlate reliably. 2, 3
Ancillary Testing Considerations
While not blood tests per se, allergy testing (skin prick, specific IgE, patch testing) is not recommended for choosing dietary restriction therapy for EoE, as targeted dietary elimination based on IgE testing is no more effective than empirical elimination. 1 Food-specific IgE/IgG antibody testing in blood or tissue samples has no established role in EoE management. 1
Aeroallergen sensitivity testing may be warranted to identify concurrent atopic conditions (present in 50-80% of EoE patients), but this serves to manage comorbid allergic disease rather than to diagnose or monitor EoE itself. 1, 2, 3