Eosinophil Count

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Eosinophil Count

Synonym/acronym: Eos count, total eosinophil count.

Common use

To assist in diagnosing conditions related to immune response such as asthma, dermatitis, and hay fever. Also used to assist in identification of parasitic infections.

Specimen

Whole blood (1 mL) collected in a lavender-top (EDTA) tube.

Normal findings

(Method: Manual count using eosinophil stain and hemocytometer or automated analyzer)

Absolute count: 50 to 500 cells/microL [SI units (0.05–0.5 × 109/L)]

Relative percentage: 1% to 4%

Description

Eosinophils are white blood cells whose function is phagocytosis of antigen-antibody complexes and response to allergy-inducing substances and parasites. Eosinophils have granules that contain histamine used to kill foreign cells in the body. Eosinophils also contain proteolytic substances that damage parasitic worms. The binding of histamine to receptor sites on cells results in smooth muscle contraction in the bronchioles and upper respiratory tract, constriction of pulmonary vessels, increased mucus production, and secretion of acid by the cells that line the stomach. The contents of eosinophilic granules are very effective in neutralizing allergens. However, the substances released by the eosinophils can also damage normal cells in the area where the histamine and other enzymes are released. Eosinophil counts can increase to greater than 30% of normal in parasitic infections; however, a significant percentage of children with visceral larva migrans infestations have normal eosinophil counts.

This procedure is contraindicated for

    N/A

Indications

  • Assist in the diagnosis of conditions such as allergies, parasitic infections, drug reactions, collagen diseases, and myeloproliferative disorders.

Potential diagnosis

Increased in

  • Eosinophils are released and migrate to inflammatory sites in response to numerous environmental, chemical/drug, or immune-mediated triggers. T cells, mast cells, and macrophages release cytokines like interlukin-3 (IL3), interlukin-5 (IL5), granulocyte/macrophage colony–stimulating factor, and chemokines like the eotaxins, which can result in the activation of eosinophils.

  • Addison’s disease (most commonly related to autoimmune destruction of adrenal glands)
  • Allergy
  • Asthma
  • Cancer
  • Dermatitis
  • Drug reactions
  • Eczema
  • Hay fever
  • Hodgkin’s disease
  • Hypereosinophilic syndrome (rare and idiopathic)
  • Löffler’s syndrome (pulmonary eosinophilia due to allergic reaction or infection from a fungus or parasite)
  • Myeloproliferative disorders (related to abnormal changes in the bone marrow)
  • Parasitic infection (visceral larva migrans)
  • Rheumatoid arthritis (possibly related to medications used in therapy)
  • Rhinitis
  • Sarcoidosis
  • Splenectomy
  • Tuberculosis

Decreased in

    Aplastic anemia (bone marrow failure) Eclampsia (shift to the left; relative to significant production of neutrophils) Infections (shift to the left; relative to significant production of neutrophils) Stress (release of cortisol suppresses eosinophils)

Critical findings

    N/A

Interfering factors

  • Numerous drugs and substances can cause an increase in eosinophil levels as a result of an allergic response or hypersensitivity reaction. These include acetophenazine, allopurinol, aminosalicylic acid, ampicillin, butaperazine, capreomycin, carisoprodol, cephaloglycin, cephaloridine, cephalosporins, cephapirin, cephradine, chloramphenicol, clindamycin, cloxacillin, dapsone, epicillin, erythromycin, fluorides, gold, imipramine, iodides, kanamycin, mefenamic acid, methicillin, methyldopa, minocycline, nalidixic acid, niridazole, nitrofurans (including nitrofurantoin), NSAIDs, nystatin, oxamniquine, penicillin, penicillin G, procainamide, ristocetin, streptokinase, streptomycin, tetracycline, triamterene, tryptophan, and viomycin.
  • Drugs that can cause a decrease in eosinophil levels include acetylsalicylic acid, amphotericin B, corticotropin, desipramine, glucocorticoids, hydrocortisone, interferon, niacin, prednisone, and procainamide.
  • Clotted specimens should be rejected for analysis.
  • Specimens more than 4 hr old should be rejected for analysis.
  • There is a diurnal variation in eosinophil counts. The count is lowest in the morning and continues to rise throughout the day until midnight. Therefore, serial measurements should be performed at the same time of day for purposes of continuity.

Nursing Implications and Procedure

Pretest

  • Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
  • Patient Teaching:   Inform the patient this test can assist in diagnosing immune response conditions and parasitic infections.
  • Obtain a history of the patient’s complaints, including a list of known allergens, especially allergies or sensitivities to latex.
  • Obtain a history of the patient’s hematopoietic, immune, and respiratory systems; symptoms; and results of previously performed laboratory tests and diagnostic and surgical procedures.
  • Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values).
  • Review the procedure with the patient. Inform the patient that specimen collection takes approximately 5 to 10 min. Address concerns about pain and explain that there may be some discomfort during the venipuncture.
  • Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
  • Note that there are no food, fluid, or medication restrictions unless by medical direction.

Intratest

  • Potential complications: N/A
  • Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
  • Instruct the patient to cooperate fully and to follow directions. Direct the patient to breathe normally and to avoid unnecessary movement.
  • Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient, and label the appropriate specimen container with the corresponding patient demographics, initials of the person collecting the specimen, date, and time of collection. Perform a venipuncture.
  • Remove the needle and apply direct pressure with dry gauze to stop bleeding. Observe/assess venipuncture site for bleeding or hematoma formation and secure gauze with adhesive bandage.
  • Promptly transport the specimen to the laboratory for processing and analysis.

Post-Test

  • Inform the patient that a report of the results will be made available to the requesting HCP, who will discuss the results with the patient.
  • Nutritional Considerations: Consideration should be given to diet if food allergies are present.
  • Instruct the patient with an elevated eosinophil count to report any signs or symptoms of infection, such as fever.
  • Instruct the patient with an elevated count to rest and take medications as prescribed, to increase fluid intake as appropriate, and to monitor temperature.
  • Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. Answer any questions or address any concerns voiced by the patient or family.
  • Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.

Related Monographs

  • Related tests include allergen-specific immunoglobulin E, biopsy bone marrow, blood gases, CBC, culture stool, ESR, fecal analysis, hypersensitivity pneumonitis screen, IgE, lung perfusion scan, ova and parasites, plethysmography, and PFT.
  • Refer to the Hematopoietic, Immune, and Respiratory systems tables at the end of the book for related tests by body system.
References in periodicals archive ?
1 Eosinophilia is generally considered when the total eos count is greater than 450-500 eos/[micro]L of blood and is most often associated with parasitic infections, some bacterial infections, drug or other allergies, respiratory disorders, GI disorders, certain immunodeficiences, various malignancies and leukemias, and connective tissue diseases.