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Eosinophil count

Nursing2019 Critical Care: May 2019 - Volume 14 - Issue 3 - p 32
doi: 10.1097/
Department: Looking at Labs
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An eosinophil count measures the number of eosinophils in peripheral blood. Eosinophils, capable of phagocytosis, ingest antigen-antibody complexes and become active in the later stages of inflammation. Eosinophils respond to allergic and parasitic diseases. Eosinophilic granules contain histamine and account for one-third of all the histamine in the body. Eosinophilia occurs when there is an increased number of circulating eosinophils; conversely, eosinopenia occurs when there is a decreased number of circulating eosinophils. This test is used to diagnose allergic disorders, assess severity of parasitic infections, and monitor response to treatment.

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Normal reference values in adults

Absolute eosinophil count (determined by multiplying the total white blood cell (WBC) count by the percentage of eosinophils): 0 to 500 cells/mcL (<0.5 x 109/L)

Differential: 0%-3% of total WBC count

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Possible causes of eosinophilia

(>5% or >0.5 x 109/L)

  • allergies, asthma
  • parasitic disease
  • some endocrine disorders, such as Addison disease, hypopituitarism
  • Hodgkin disease and myeloproliferative disorders, chronic myeloid leukemia, polycythemia vera
  • chronic skin diseases, such as eczema
  • some infections, such as HIV
  • idiopathic hypereosinophilic syndrome and autoimmune and idiopathic disorders, such as sarcoidosis, inflammatory bowel disease, immunoglobulin G4-related disease, and other connective tissue disorders and immunodeficiency disorders
  • aspirin sensitivity, allergic drug reactions
  • poisons, such as phosphorus
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Possible causes of eosinopenia

(<1% or 0.0 cells/mm3 or 0.0 x 109/L)

Eosinopenia is usually caused by an increased adrenal steroid production that accompanies most stress disorders and is associated with:

  • Cushing syndrome
  • use of certain drugs, such as epinephrine, thyroxin
  • acute bacterial infections
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Interfering factors

  • Normal eosinophil count is lowest in the morning, then rises from noon until after midnight. For this reason, serial eosinophil counts should be repeated at the same time each day.
  • Stressful situations, such as burns, trauma, and postoperative states, cause a decreased eosinophil count.
  • After administration of corticosteroids, eosinophils disappear.

Sources: Fischbach FT, Fischbach MA. A Manual of Laboratory and Diagnostic Tests. 10th ed. Philadelphia, PA: Wolters Kluwer; 2018. Wei S, Kao LS. Eosinopenia and adverse outcomes after Clostridium difficile infections: of mice and men. JAMA Surg. 2018;153(12):1133-1134. Matono T, Kutsuna S, Kato Y. Role of classic signs as diagnostic predictors for enteric fever among returned travellers: relative bradycardia and eosinopenia. PLoS ONE. 2017;12(6):e0179814.

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