From the Guidelines
The workup for eosinophilia should begin with a thorough history and physical examination, including assessment of travel, new medications, recurrent history of infections, and/or family history of eosinophilia, as recommended by the NCCN clinical practice guidelines in oncology 1. This initial evaluation is crucial in identifying potential causes of eosinophilia, such as infections, allergies, or immunodeficiency syndromes.
Key Components of the Workup
- A complete blood count with differential to confirm eosinophil elevation (normal range is typically 0-500 cells/μL)
- Comprehensive metabolic panel
- Stool examination for ova and parasites
- Additional first-line tests, such as IgE levels, chest X-ray, and urinalysis, may be considered based on the patient's history and symptoms 1.
Further Investigations
If the cause remains unclear, second-tier investigations may include:
- Specific parasite serologies
- CT scans of chest and abdomen
- Skin testing for allergies
- Evaluation for hematologic disorders with peripheral blood smear and possibly bone marrow examination For suspected organ involvement, targeted testing such as pulmonary function tests, echocardiogram, or specific organ biopsies may be necessary 1.
Importance of Identifying the Underlying Cause
Identifying the underlying cause of eosinophilia is crucial, as treatment depends on addressing the specific etiology rather than the eosinophilia itself. The workup should progress from common to rare causes, with consideration of both reactive eosinophilia (secondary to infection, allergy, or medication) and primary eosinophilic disorders. By following this systematic approach, clinicians can provide effective management and improve patient outcomes, reducing the risk of morbidity, mortality, and impact on quality of life.
From the Research
Workup for Eosinophilia
The workup for eosinophilia involves a thorough approach to determine the underlying cause of the condition. The following steps are recommended:
- Determine the absolute eosinophil count (AEC) by multiplying the percentage of eosinophils by the total white blood cell count 2
- Define eosinophilia as an AEC of >500 eosinophils/μL and hypereosinophilia as an AEC of ≥1500 eosinophils/μL 2
- Conduct a meticulous medical history to assess increased AECs and narrow the list of possible etiologies 2
- Pay special attention to the onset of eosinophilia and any coincident events, such as travel or the start of new medications 2
- Identify any possible eosinophil-associated end-organ damage, and consider a biopsy of suspected involved areas for confirmation 2
Diagnostic Approach
The diagnostic approach for eosinophilia should include:
- A detailed history and physical examination to elicit eosinophilic organ involvement 3
- Histological confirmation whenever possible 3
- Serologic, blood, and bone marrow cell analyses, genetic testing, and radiologic imaging to distinguish many of the causes 3
- Input from specialists, such as hematology, dermatology, pulmonary, gastroenterology, and neurology, to help narrow down the possibilities and eventually result in a specific diagnosis 3
Key Considerations
Key considerations in the workup for eosinophilia include:
- Eosinophilia can be caused by a wide variety of allergic, rheumatologic, infectious, neoplastic, and rare idiopathic disorders 4
- The prognosis and choice of treatment depend on the degree of eosinophilia, severity of organ involvement, and etiology of the eosinophilia 4
- A rational approach to diagnosis and treatment is necessary to distinguish many of the causes and choose the optimal treatment for a particular condition 3