What is the appropriate workup for eosinophilia (Eosinophilia is a condition characterized by an elevated eosinophil count)?

From the Guidelines

The workup for eosinophilia should begin with a complete blood count with differential to confirm the elevation (>0.45 x 10^9/L) and assess its severity, as defined by 1. Initial evaluation should include a thorough history focusing on travel, medications, allergies, and symptoms of parasitic infections or autoimmune disorders. Physical examination should look for skin lesions, lymphadenopathy, and organomegaly. First-line laboratory tests include comprehensive metabolic panel, urinalysis, stool examination for ova and parasites (three samples), serum IgE levels, and specific IgE testing for common allergens. If travel history suggests parasitic infection, serologic testing for specific parasites like Strongyloides should be performed, as recommended by 1. For persistent unexplained eosinophilia, additional testing may include chest imaging, pulmonary function tests, and evaluation for hematologic malignancies with peripheral blood smear, flow cytometry, and bone marrow examination. Testing for autoimmune conditions with ANA, ANCA, and rheumatoid factor may be warranted based on clinical presentation. Management depends on identifying the underlying cause, with treatment directed at the specific etiology. Glucocorticoids may be used for symptomatic hypereosinophilic syndrome, typically starting with prednisone 1 mg/kg/day with gradual tapering based on clinical response, as eosinophilia can indicate various conditions ranging from benign allergic reactions to life-threatening disorders, so systematic evaluation is essential for proper diagnosis and treatment, as noted in 1.

Some key points to consider in the workup and management of eosinophilia include:

• The importance of travel history in identifying potential parasitic infections, as highlighted by 1 and 1
• The need for thorough laboratory testing, including stool examination for ova and parasites and serologic testing for specific parasites
• The potential for non-infectious causes of eosinophilia, such as autoimmune disorders or hematologic malignancies, and the need for additional testing to rule out these conditions
• The use of glucocorticoids in the management of symptomatic hypereosinophilic syndrome, as noted in 1.

Overall, a systematic and thorough approach to the workup and management of eosinophilia is essential to ensure proper diagnosis and treatment, and to prevent potential complications, as emphasized by 1 and 1.

From the Research

Definition and Classification of Eosinophilia

• Eosinophilia is defined as an absolute eosinophil count (AEC) of >500 eosinophils/μL, while hypereosinophilia is defined as an AEC of ≥1500 eosinophils/μL 2
• The causes of eosinophilia are broad and can be secondary to allergies, infections, medication reactions, autoimmune diseases, or other conditions 2
• Hypereosinophilia is rarely explained by allergy alone and should always prompt a further workup 2

Diagnostic Approach

• The first step in evaluating eosinophilia is to determine the AEC, which is calculated from multiplying the percentage of eosinophils by the total white blood cell count 2
• A meticulous approach to exploring key aspects of the medical history is recommended, including the onset of eosinophilia, coincident events, and possible eosinophil-associated end-organ damage 2
• Diagnostic evaluation of primary eosinophilias relies on morphologic review of the blood and marrow, standard cytogenetics, fluorescence in situ hybridization, next generation sequencing gene assays, and flow immunophenotyping 3

Treatment and Management

• The goal of therapy is to mitigate eosinophil-mediated organ damage 3
• For patients with milder forms of eosinophilia without symptoms or signs of organ involvement, a watch and wait approach with close follow-up may be undertaken 3
• Corticosteroids are first-line therapy for patients with lymphocyte-variant hypereosinophilic syndrome (HES) and idiopathic HES 3, 4
• Hydroxyurea and interferon-α have demonstrated efficacy as initial treatment and in steroid-refractory cases of HES 5, 3, 4
• Mepolizumab, an interleukin-5 (IL-5) antagonist monoclonal antibody, was recently approved by the US Food and Drug Administration for patients with idiopathic HES 3