Do plasma eosinophils (white blood cells) increase in patients with Eosinophilic Esophagitis (EE)?

Peripheral Blood Eosinophils in Eosinophilic Esophagitis

Peripheral blood eosinophil counts may be elevated in 40-50% of patients with Eosinophilic Esophagitis (EoE), but are not consistently increased and cannot be used as a reliable diagnostic marker for the disease.

Peripheral Eosinophilia in EoE

Peripheral blood eosinophilia is a common but inconsistent finding in patients with EoE:

• Studies show that approximately 40-50% of adults and 20-100% of children with EoE have elevated peripheral eosinophil counts (>300-350 per mm³) 1
• The elevation is typically modest (about 2-fold increase) 1
• Peripheral eosinophil counts can correlate with tissue eosinophilia in some patients with EoE 1
• Changes in peripheral eosinophilia should be interpreted considering:
  • Patient's age
  • Adherence to aeroallergen avoidance
  • Pollen season
  • Control of comorbid allergic diseases 1

Diagnostic Value and Limitations

• Peripheral eosinophil counts alone have insufficient sensitivity and specificity to serve as a standalone diagnostic marker for EoE 1
• When combined with other markers like plasma eosinophil-derived neurotoxin (EDN), the diagnostic value improves (sensitivity 63%, specificity 92%, positive predictive value 83%, negative predictive value 79%) 1, 2
• Peripheral blood eosinophil counts may decrease after successful treatment with topical corticosteroids 1

Relationship with Disease Activity

• In some patients, persistent blood eosinophilia correlates with persistent dysphagia 1
• One study demonstrated that the degree of elevation of serum eosinophils correlated with the severity of EoE 1
• Blood eosinophil counts, plasma EDN levels, and eotaxin-3 levels significantly correlate with esophageal eosinophil density 2

Clinical Context

• EoE is defined by a pathological eosinophilic infiltrate in the esophageal mucosa (≥15 eosinophils per high-powered field) 1, 3
• The majority of EoE patients (50-80%) have concurrent atopic conditions such as asthma, allergic rhinitis, and/or eczema 1
• These concurrent allergic conditions can independently contribute to peripheral eosinophilia 1
• According to general eosinophilia guidelines, eosinophilia is defined as a peripheral blood eosinophil count >0.5 × 10⁹/L, with severity classified as mild (>0.5 × 10⁹/L), moderate (>1.5 × 10⁹/L), or severe (>5.0 × 10⁹/L) 4

Clinical Recommendations

• Evaluation of peripheral blood eosinophils may provide supportive evidence for EoE but is not diagnostic 1
• A thorough evaluation by an allergist or immunologist is recommended due to the high rates of concurrent atopic diseases 1
• When monitoring treatment response, blood eosinophil counts should be drawn at diagnosis and again at each evaluation for response to treatment (dietary or medical) 1
• Esophageal biopsies remain mandatory for the diagnosis of EoE, as peripheral markers cannot replace histopathological confirmation 1, 5

Potential Biomarkers for EoE

Research is ongoing to identify reliable non-invasive biomarkers for EoE:

• Plasma EDN and eotaxin-3 levels show promise as potential biomarkers 2
• Other candidate biomarkers include IL-5, IL-13, IL-15, and basic fibroblast growth factor 1
• Currently, there is insufficient evidence to support the clinical utility of any single peripheral marker as a surrogate disease indicator of histologic inflammation in EoE 1

In conclusion, while peripheral blood eosinophil counts may be elevated in some patients with EoE and can correlate with disease activity in certain cases, they lack the sensitivity and specificity to serve as a reliable diagnostic marker for the disease. Esophageal biopsies remain the gold standard for diagnosis.