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Lab Test: Eosinophil Count

    Lab Test
    • Eosinophil Count
    • Measurement of eosinophils in whole blood for the evaluation and management of allergic, hematologic, and infectious diseases, as well as parasitic infestations
    Reference Range
    • Adults:
      • Relative:  0%-8%
      • Absolute:  0-0.45 cells X 109/L
    • Neonates, birth to 28 days:
      • Absolute:  0-0.9 X 103 cells/microL
    • Infants, 1 week to 6 months:
      • Absolute:  0.2-0.3 X 103 cells/microL
    • Infants, 1 year:
      • Relative:  2.6%
      • Absolute:  0.3 X 103 cells/microL
    • Infants, 2 years:
      • Absolute:  0-0.7 X 103 cells/microL
    • Children, 4 to 10 years:
      • Relative:  2.4%-2.8%
      • Absolute:  0-0.6 X 103 cells/microL
    Indications & Uses
    • Evaluation of asthma severity - the eosinophil count is normally only 2% to 3%, but in asthmatics, the count may be elevated to 5% or more, and the absolute total eosinophil count may increase to more than 350/mm3.  Elevated eosinophil count in asthma is a marker of severity and risk of death. 
    • HIV/AIDS - eosinophilia in HIV infection is associated with a high incidence of cutaneous disease (e.g., atopic dermatitis, eosinophilic pustular folliculitis), but not with other conditions commonly associated with eosinophilia (e.g., parasitic infections, malignancy, allergic reactions).  Therefore, extensive work-up for asymptomatic eosinophilia in HIV-infected persons with cutaneous disease is probably unwarranted. 
    • Suspected anisakiasis - modest eosinophilia from 30% to 40% is a common finding in patients with gastric anisakiasis. 
    • Suspected atopic dermatitis - eosinophilia is associated with atopic dermatitis, particularly in conjunction with respiratory allergic disease. Elevated counts during infancy is predictive of allergic disease during the first six years of life.
    • Suspected hypereosinophilic syndrome - in the absence of other known causes, absolute eosinophil counts at or above 1500 cells/microL sustained for at least 6 months, in conjunction with organ damage, may be classified as hypereosinophilic syndrome. 
    • Suspected schistosomiasis - during the acute phase, eosinophilia may be as high as 70%. 
    • Suspected Strongyloidesinfection - tissue-invasive parasitosis, including strongyloidiasis, is a common cause of secondary eosinophilia, with values often exceeding 400 cells/microL. 
    • Suspected Trichnella spiralis infection (trichinosis) - eosinophilia occurs in more than 50% of cases of trichinosis.  Typically levels rise within days, peak during the third or fourth week, then gradually decline over a period of months.  Trichinosis is associated with a relative eosinophilia of at least 20%, commonly exceeds 50%, and may reach a maximum of 90%.  An absolute eosinophil count of 350 to 3,000/microL is associated with 75% of trichinosis cases.  Twenty percent of patients have eosinophil counts of 3,000 to 8,000/microL, while few cases may have normal or near-normal values.  Absolute eosinophil counts as high as 15 X 109/L have been noted.
    Clinical Application
    • White blood cells are divided into granulocytes and nongranulocytes.  Granulocytes include neutrophils, basophils, and eosinophils.  Eosinophils are involved in the allergic reaction.  They are capable of phagocytosis of antigen-antibody complexes.  As the allergic response diminishes, the eosinophil count decreases.  They do not respond to bacterial or viral infections. 
    • An elevated eosinophils count may be caused by:
      • "eosinophilia", parasitic infections, allergic reactions, eczema, leukemia, or autoimmune diseases
    • A decreased eosinophils count may be caused by:
      • "eosinopenia" or increased adrenosteroid production
    Related Tests

    Complete blood count with automated differential

    Drug-Lab Interactions
    • Results increased in smoking
    • Results decreased in labor
    Test Tube Needed
    • Purple top EDTA tube
    • Collect whole blood sample or use capillary blood
    • Apply pressure or a pressure dressing to the venipuncture site and check the site for bleeding.
    What To Tell Patient Before & After
    • Explain the procedure to the patient.
    • Tell the patient that no fasting is required.
    • LaGow B et al., eds. PDR Lab Advisor. A Comprehensive Point-of-Care Guide for Over 600 Lab Tests.  First ed. Montvale, NJ: Thomson PDR; 2007.
    • Pagana K, Pagana TJ eds. Mosby's Manual of Diagnostic and Laboratory Tests. 5th Ed.  St. Louis, Missouri. 2014.

MESH Terms & Keywords

  • Eosinophil