Interpretation of 24% Eosinophils on CBC
A blood eosinophil count of 24% on a CBC is significantly elevated and indicates an underlying eosinophilic disorder that requires further investigation to determine the specific cause.
Normal Values and Classification
- Normal eosinophil percentage in peripheral blood is 1-3% of total leukocytes 1
- Eosinophilia is defined as a peripheral blood eosinophil count >0.5 × 10⁹/L 2
- Severity classification:
- Mild: 0.5-1.5 × 10⁹/L
- Moderate: 1.5-5.0 × 10⁹/L
- Severe: >5.0 × 10⁹/L 2
Potential Causes of Elevated Eosinophils (24%)
Allergic/Atopic Conditions
- Allergic rhinitis, asthma, or eczema 3
- Eosinophilic asthma (particularly if counts fluctuate seasonally) 3
- Chronic rhinosinusitis with nasal polyps 3
Gastrointestinal Disorders
- Eosinophilic esophagitis (EE) - 10-50% of adults and 20-100% of children with EE have elevated peripheral eosinophil counts 3
- Other eosinophilic gastrointestinal disorders
Hematologic Disorders
- Myeloid/lymphoid neoplasms with eosinophilia and rearrangement of PDGFRA, PDGFRB, or FGFR1 3
- Chronic eosinophilic leukemia, not otherwise specified (CEL, NOS) 2
- Hypereosinophilic syndrome (HES) 2
Parasitic Infections
- Various helminthic infections can cause marked eosinophilia 4
Other Causes
- Drug reactions
- Autoimmune disorders
- Certain vasculitides (e.g., eosinophilic granulomatosis with polyangiitis)
Recommended Diagnostic Approach
Initial Evaluation
Complete history and physical examination:
- Focus on allergic symptoms, respiratory symptoms, gastrointestinal complaints
- Medication review for potential drug reactions
- Travel history for parasitic infections
- Skin examination for rashes or lesions
Laboratory testing:
- Complete blood count with differential (to confirm eosinophilia)
- Peripheral blood smear (to evaluate blood cell morphology)
- Comprehensive metabolic panel with liver function tests
- Serum tryptase (to evaluate mast cell activation)
- IgE levels (often elevated in allergic disorders) 3
Specialized testing based on clinical suspicion:
Tissue Evaluation
- Tissue biopsy may be necessary if organ involvement is suspected:
Clinical Implications and Management
Prognostic Significance
- Persistent blood eosinophilia correlates with persistent symptoms in some conditions 3
- The degree of elevation may correlate with disease severity 3
- In some respiratory infections, eosinophilia may indicate better prognosis 4
Treatment Considerations
- Treatment depends on the underlying cause:
- Allergic disorders: antihistamines, corticosteroids, allergen avoidance
- Eosinophilic esophagitis: proton pump inhibitors, topical corticosteroids, elimination diets 1
- Hematologic disorders: targeted therapies (e.g., imatinib for PDGFRA/B rearrangements) 3
- Hypereosinophilic syndrome: corticosteroids, hydroxyurea, interferon-α, or IL-5 antagonists 2
Important Considerations
- A single elevated eosinophil count should be confirmed with repeat testing 5
- Eosinophil counts can vary seasonally (up to 20% difference between summer and winter) 5
- Smoking can decrease eosinophil levels by approximately 23% 5
- Counts between 150-299 cells/μL show the greatest variability over time 5
Follow-up Recommendations
- Regular monitoring of blood counts to track response to treatment
- Evaluation for end-organ damage in cases of persistent eosinophilia
- Referral to specialists (allergist, hematologist, gastroenterologist) based on suspected etiology
A 24% eosinophil count is markedly elevated and warrants prompt and thorough evaluation to identify the underlying cause and prevent potential end-organ damage.