From the Guidelines
The workup for elevated eosinophils should begin with a thorough history and physical examination, focusing on potential causes such as allergies, medications, parasitic infections, and autoimmune disorders, and initial laboratory testing should include a complete blood count with differential to confirm eosinophilia (>500 eosinophils/μL) 1. The initial evaluation should also consider the patient's travel history, as helminth infections are a common cause of eosinophilia in returning travelers and migrants 1. Key points to consider in the workup include:
- Initial laboratory testing: complete blood count with differential, comprehensive metabolic panel, and stool examination for ova and parasites
- Additional first-line tests: IgE levels, erythrocyte sedimentation rate, and C-reactive protein
- Consideration of medication-induced eosinophilia and discontinuation of potential offending agents
- Second-line testing for persistent unexplained eosinophilia: chest imaging, specific parasite serologies based on travel history, and testing for specific autoimmune markers like ANCA or specific IgE
- Bone marrow examination may be necessary to rule out hematologic malignancies if peripheral eosinophilia persists without an identified cause
- Consultation with specialists in allergy/immunology, infectious disease, or hematology is recommended for eosinophil counts exceeding 1,500/μL or when associated with organ dysfunction 1. The urgency of the workup depends on the degree of eosinophilia and presence of end-organ damage, with severe eosinophilia (>5,000/μL) requiring more immediate evaluation due to the risk of eosinophilic tissue infiltration and subsequent damage to the heart, lungs, and nervous system. It is also important to note that allergy testing to foods (skin prick, specific IgE, patch testing) is not recommended for choosing the type of dietary restriction therapy for eosinophilic oesophagitis, as the evidence suggests that targeted dietary elimination on the basis of IgE testing is no more effective than empirical dietary elimination 1.
From the FDA Drug Label
mast cells, eosinophils, neutrophils, macrophages, lymphocytes) and mediators (e.g., histamine, eicosanoids, leukotrienes, cytokines) are involved in inflammation. Mepolizumab, by inhibiting IL-5 signaling, reduces the production and survival of eosinophils; The pharmacodynamic response (blood eosinophil reduction) following repeat doses of mepolizumab administered subcutaneously or intravenously was evaluated in adult subjects with asthma and blood eosinophil levels >200 cells/mcL.
The work up for elevated eosinophils may involve evaluating the patient's inflammatory response and eosinophil levels. Mepolizumab has been shown to reduce blood eosinophil levels in a dose-dependent manner, with a geometric mean reduction of 64% to 90% observed in clinical trials 2. Key considerations in the work up may include:
- Eosinophil count: Evaluating the patient's blood eosinophil levels to determine the severity of the elevation.
- Inflammatory markers: Assessing other inflammatory markers, such as histamine, eicosanoids, leukotrienes, and cytokines, to understand the underlying inflammatory response.
- IL-5 signaling: Considering the role of IL-5 signaling in the production and survival of eosinophils, and potentially evaluating the patient's response to IL-5 inhibition.
From the Research
Workup for Elevated Eosinophils
The workup for elevated eosinophils involves a thorough approach to determine the underlying cause of eosinophilia.
- A detailed history and physical examination are essential to identify potential eosinophilic organ involvement 3.
- The differential diagnosis of hypereosinophilia is extensive, and a rational approach is necessary to distinguish between various causes 3.
- Diagnostic tests may include:
- Serologic tests
- Blood cell analyses
- Bone marrow cell analyses
- Genetic testing
- Radiologic imaging 3
- Input from specialists, such as hematologists, dermatologists, pulmonologists, gastroenterologists, and neurologists, may be necessary to narrow down the possibilities and arrive at a specific diagnosis 3.
Conditions Associated with Eosinophilia
Eosinophilia can be associated with a wide range of conditions, including:
- Allergic diseases
- Parasitic diseases
- Autoimmune diseases
- Connective tissue diseases
- Rheumatologic diseases
- Primary eosinophilia, such as hypereosinophilic syndrome
- Malignant states 4, 5, 6
Treatment Options
Treatment options for eosinophilia depend on the underlying cause and may include: