What is the appropriate management for elevated eosinophils (eosinophilia)?

Management of Elevated Eosinophils (Eosinophilia)

The appropriate management of eosinophilia requires a systematic diagnostic approach followed by targeted treatment based on the underlying cause, with empirical treatment with albendazole 400 mg plus ivermectin 200 μg/kg recommended for asymptomatic eosinophilia in travelers/migrants with negative initial testing. 1

Definition and Classification

• Eosinophilia is defined as a peripheral blood eosinophil count >0.5 × 10⁹/L 1, 2
• Severity classification:
  • Mild: >0.5 × 10⁹/L
  • Moderate: >1.5 × 10⁹/L (hypereosinophilia)
  • Severe: >5.0 × 10⁹/L 1

Diagnostic Approach

Initial Evaluation

1. Detailed clinical history:

   • Travel to tropical/subtropical areas
   • Exposure to freshwater
   • Consumption of raw foods
   • Walking barefoot
   • Current and recent medications
   • Allergy history 1

2. Essential laboratory tests:

   • Complete blood count with differential
   • Peripheral blood smear
   • Comprehensive metabolic panel with liver function tests
   • Urinalysis with protein-to-creatinine ratio
   • C-reactive protein
   • Serum tryptase
   • Vitamin B12 levels 1

3. Parasite-specific testing:

   • Microscopic examination of concentrated stool samples (3 samples)
   • Serological tests based on geographical exposure
   • Strongyloides serology (particularly important) 3, 1
   • HIV testing as recommended by guidelines 3

Secondary Diagnostic Tests

• Perianal swab or adhesive tape test for pinworm
• Tissue biopsy if organ involvement is suspected
• Specialized tests based on suspected cause (PCR, serology) 3, 1

Treatment Algorithm

1. For Asymptomatic Eosinophilia in Travelers/Migrants

• Empirical treatment with:
  • Albendazole 400 mg (single dose) PLUS
  • Ivermectin 200 μg/kg (single dose) 3, 1
  • Important: Exclude Loa loa in people who have traveled to endemic regions BEFORE treating with ivermectin 3
  • For children aged 12-24 months, consult with an expert 3

2. For Specific Parasitic Infections

• Hookworm: Albendazole 400 mg daily for 3 days 1
• Schistosomiasis: Praziquantel 40 mg/kg twice daily for 5 days 1
  • For acute schistosomiasis (Katayama syndrome): Praziquantel plus possible corticosteroids 3, 1
  • Repeat treatment at 8 weeks to treat any residual worms 3
• Strongyloidiasis: Ivermectin 200 μg/kg/day for 1-2 days 1
• Filariasis: Seek specialist advice; exclude co-existing onchocerciasis 3
• Cutaneous larva migrans: Ivermectin (200 μg/kg single dose) or Albendazole (400 mg/day for 3 days) 1

3. For Drug-Induced Eosinophilia

• Immediate withdrawal of the causative medication 1

4. For Persistent Unexplained Eosinophilia

• Refer to specialists (hematology, allergy/immunology) for further evaluation 1, 4
• Consider evaluation for hypereosinophilic syndromes, including genetic testing for myeloid/lymphoid neoplasms with eosinophilia 5

Monitoring and Follow-up

• Regular monitoring of blood counts to confirm resolution 1
• For mild, transient eosinophilia: Follow-up CBC to confirm resolution 1
• For persistent eosinophilia: Regular monitoring for end-organ damage 1, 5

Important Considerations and Pitfalls

1. Beware of persistent hypereosinophilia: Levels >1.5 × 10⁹/L for >3 months can cause significant organ damage (cardiac, pulmonary, neurological) 1, 5, 6

2. Don't miss strongyloidiasis: High prevalence in migrant populations with asymptomatic eosinophilia; concentrated stool microscopy has lower sensitivity for Strongyloides 3

3. Medication review is crucial: Many medications can cause eosinophilia, and discontinuation is often the only treatment needed 1, 6

4. Allergy alone rarely explains hypereosinophilia: While allergies commonly cause mild eosinophilia, counts ≥1.5 × 10⁹/L should prompt further investigation 2

5. Consider specialist consultation: Input from hematology, dermatology, pulmonary, gastroenterology, or neurology specialists may be needed for complex cases 4

By following this systematic approach to diagnosis and treatment, clinicians can effectively manage eosinophilia while preventing potential complications from untreated causes or inappropriate therapies.