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White Blood Cell Count, Blood Smear and Differential Core Lab Study

Synonym/Acronym

WBC with diff, leukocyte count, white cell count.

Rationale

To evaluate bacterial, parasitic, and viral infections; to assist in diagnosing conditions related to immune response such as asthma, dermatitis, and hay fever; and to assist in diagnosing and monitoring leukemic disorders.

A small group of studies in this manual have been identified as Core Lab Studies. The designation is meant to assist the reader in sorting the basic “always need to know” laboratory studies from the hundreds of other valuable studies found in the manual—a way to begin putting it all together.

Normal, abnormal, or various combinations of core lab study results can indicate that all is well, reveal a problem that requires further investigation with additional testing, signal a positive response to treatment, or suggest that the health status is as expected for the associated situation and time frame.

White blood cell (WBC) count is part of a complete blood count (CBC), one of the most requested laboratory studies, and is included in the Anemia profile, General Health panel, and Obstetric panel.

Patient Preparation

There are no food, fluid, activity, or medication restrictions unless by medical direction.

Normal Findings

Method: Automated, computerized, multichannel analyzers, flow cytometry. Many analyzers can determine a five- or six-part WBC differential. The six-part automated WBC differential identifies and enumerates neutrophils, lymphocytes, monocytes, eosinophils, basophils, and immature granulocytes (IG), where IG represents the combined enumeration of promyelocytes, metamyelocytes, and myelocytes as both an absolute number and a percentage. The five-part WBC differential includes all but the immature granulocyte parameters.

WBC Count and Differential

AgeConventional Units WBC × 103/microLNeutrophilsLymphocytesMonocytesEosinophilsBasophils
(Absolute) and %(Absolute) and %(Absolute) and %(Absolute) and %(Absolute) and %
Birth9.1–30.1(5.5–18.3) 24%–58%(2.8–9.3) 26%–56%(0.5–1.7) 7%–13%(0.02–0.7) 0%–8%(0.1–0.2) 0%–2.5%
1–23 mo6.1–17.5(1.9–5.4) 21%–67%(3.7–10.7) 20%–64%(0.3–0.8) 4%–11%(0.2–0.5) 0%–3.3%(0–0.1) 0%–1%
2–10 yr4.5–13.5(2.4–7.3) 30%–77%(1.7–5.1) 14%–50%(0.2–0.6) 4%–9%(0.1–0.3) 0%–5.8%(0–0.1) 0%–1%
11 yr–older adult4.5–11.1(2.7–6.5) 40%–75%(1.5–3.7) 12%–44%(0.2–0.4) 4%–9%(0.05–0.5) 0%–5.5%(0–0.1) 0%–1%

*SI Units (conventional units × 1 or WBC count × 109/L).

WBC Count and Differential

AgeImmature Granulocytes (Absolute) (103/microL)Immature Granulocyte Fraction (IGF) (%)
Birth–9 yr0–0.030%–0.4%
10 yr–older adult0–0.090%–0.9%

Reference values for the WBC count vary across the age continuum and with physical condition. For example, counts are affected by high levels of physical activity or stress (e.g., labor and delivery). Thus, the time of collection and the activity status of the patient should be taken into consideration when reviewing or comparing WBC counts.

Critical Findings and Potential Interventions

Consideration may be given to verifying the critical findings before action is taken. Policies vary among facilities and may include requesting immediate recollection and retesting by the laboratory.

The presence of abnormal cells, other morphological characteristics, or cellular inclusions may signify a potentially life-threatening or serious health condition and should be investigated. Examples are hypersegmented neutrophils, agranular neutrophils, blasts or other immature cells, Auer rods, Döhle bodies, marked toxic granulation, and plasma cells.

Overview

Study type: Blood from a lavender-top [EDTA] tube; related body system: Circulatory/Hematopoietic and Immune systems. The specimen should be mixed gently by inverting the tube 10 times. The specimen should be analyzed within 24 hr when stored at room temperature or within 48 hr if stored at refrigerated temperature. If it is anticipated the specimen will not be analyzed within 24 hr, two blood smears should be made immediately after the venipuncture and submitted with the blood sample. Smears made from specimens older than 24 hr may contain an unacceptable number of misleading artifactual abnormalities of the WBCs, such as necrobiotic WBCs.

WBCs constitute the body’s primary defense system against foreign organisms, tissues, and other substances. The life span of a normal WBC is 13 to 20 days. Old WBCs are destroyed by the lymphatic system and excreted in the feces. Reference values for WBC counts vary significantly with age. WBC counts vary diurnally, with counts being lowest in the morning and highest in the late afternoon. Other variables such as stress and high levels of activity or physical exercise can trigger transient increases of 2 × 103/microL to 5 × 103/microL. The main WBC types are neutrophils (band and segmented neutrophils), eosinophils, basophils, monocytes, and lymphocytes. WBCs are produced in the bone marrow. B-cell lymphocytes remain in the bone marrow to mature. T-cell lymphocytes migrate to and mature in the thymus. An increased WBC count is termed leukocytosis, and a decreased WBC count is termed leukopenia.

A total WBC count indicates the degree of response to a pathological process, but a more complete evaluation for specific diagnoses for any one disorder is provided by the differential count. The WBCs in the count and differential are reported as an absolute value and as a percentage. The relative percentages of cell types are arrived at by basing the enumeration of each cell type on a 100-cell count. The absolute value is obtained by multiplying the relative percentage value of each cell type by the total WBC count. For example, on a CBC report, with a total WBC of 9 × 103/microL and WBC differential with 92% segmented neutrophils, 1% band neutrophils, 5% lymphocytes, and 1% monocytes the absolute values are calculated as follows: 92/100 × 9 = 8.3 segs, 1/100 × 9 = 0.09 bands, 5/100 × 9 = 0.45 lymphs, 1/100 × 9 = 0.1 monos for a total of 9 WBC count. The absolute neutrophil count (ANC) for this patient would be 9 × (0.92 + 0.01) = 8.4.

The WBC count can be performed alone with the differential cell count or as part of the complete blood count (CBC). The WBC differential can be performed by an automated instrument or manually on a slide prepared from a stained peripheral blood sample. Automated instruments provide excellent, reliable information, but the accuracy of the WBC count can be affected by the presence of circulating nucleated red blood cells (RBCs), clumped platelets, fibrin strands, cold agglutinins, cryoglobulins, intracellular parasitic organisms, or other significant blood cell inclusions and may not be identified in the interpretation of an automated blood count. The decision to report a manual or automated differential is based on specific criteria established by the laboratory. The criteria are designed to identify findings that warrant further investigation or confirmation by manual review.

The ANC reflects the number of segmented and band type neutrophils in the total WBC count. It is used as an indicator of immune status because it reflects the type and number of WBC available to rapidly respond to an infection. Neutropenia is a decrease below normal in the number of neutrophils. ANC !!Calculator!!= Total WBC × [(Segs/100) + (Bands/100)] or total WBC × (% Segs + % Bands). The normal value varies with age but in general mild neutropenia is less than 1.5, moderate neutropenia is between 0.5 and 1, and severe neutropenia is less than 0.5. The ANC is helpful when managing patients receiving chemotherapy. It can drive decisions to place a hospitalized patient in isolation in order to protect the patient from exposure to infectious agents. Patients who are aware of their ANC can also make informed decisions in taking actions to avoid exposure to crowds, avoid touching things in public places that may carry germs, or avoid friends and family who may be sick.

Acute leukocytosis is initially accompanied by changes in the WBC count population, followed by changes within the individual WBCs. Leukocytosis usually occurs by way of increase in a single WBC family rather than a proportional increase in all cell types. Toxic granulation and vacuolation are commonly seen in leukocytosis accompanied by a shift to the left, or increase in the percentage of immature neutrophils to mature segmented neutrophils. An increased number or percentage of immature granulocytes, reflected by a shift to the left, represents production of WBCs and is useful as an indicator of infection. Immature neutrophils are called bands and can represent 3% to 5% of total circulating neutrophils in healthy individuals. Bandemia is defined by the presence of greater than 6% to 10% band neutrophils in the total neutrophil cell population. These changes in the white cell population are most commonly associated with an infectious process, usually bacterial, but they can occur in healthy individuals who are under stress (in response to epinephrine production), such as women in childbirth and very young infants. The WBC count and differential of a woman in labor or of an actively crying infant may show an overall increase in WBCs with a shift to the left. Before initiating any kind of intervention, it is important to determine whether an increased WBC count is the result of a normal condition involving physiological stress or a pathological process. The use of multiple specimen types may confuse the interpretation of results in infants. Multiple samples from the same collection site (i.e., capillary versus venous) may be necessary to obtain an accurate assessment of the WBC picture in these young patients.

Neutrophils

Neutrophils are normally found as the predominant WBC type in the circulating blood. Also called polymorphonuclear cells, they are the body’s first line of defense through the process of phagocytosis. They also contain enzymes and pyogenes, which combat foreign invaders.

Lymphocytes

Lymphocytes are agranular, mononuclear blood cells that are smaller than granulocytes. They are found in the next highest percentage in normal circulation. Lymphocytes are classified as B cells and T cells. Both types are formed in the bone marrow, but B cells mature in the bone marrow and T cells mature in the thymus. Lymphocytes play a major role in the body’s natural immune defense system. B cells differentiate into immunoglobulin-synthesizing plasma cells. T cells function as cellular mediators of immunity and comprise helper/inducer (CD4) lymphocytes, delayed hypersensitivity lymphocytes, cytotoxic (CD8 or CD4) lymphocytes, and suppressor (CD8) lymphocytes.

Monocytes

Monocytes are mononuclear cells similar to lymphocytes, but they are related more closely to granulocytes in terms of their function. They are formed in the bone marrow from the same cells as those that produce neutrophils. The major function of monocytes is phagocytosis. Monocytes stay in the peripheral blood for about 70 hr, after which they migrate into the tissues and become macrophages.

Eosinophils

The main function of eosinophils is response to allergy-inducing substances and parasites and phagocytosis of antigen-antibody complexes. 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.

A nasal smear can be examined for the presence of eosinophils to screen for allergic conditions. Either a single smear or smears of nasal secretions from each side of the nose should be submitted, at room temperature, for Hansel staining and evaluation. Normal findings vary by laboratory, but generally, greater than 10% to 15% is considered eosinophilia, or increased presence of eosinophils.

Basophils

Basophils are found in small numbers in the circulating blood. They have a phagocytic function and, similar to eosinophils, contain numerous specific granules. Basophilic granules contain heparin, histamines, and serotonin. Basophils may also be found in tissue and as such are classified as mast cells. Basophilia is noted in conditions such as leukemia, Hodgkin disease, polycythemia vera, ulcerative colitis, nephrosis, and chronic hypersensitivity states.

Indications

Interfering Factors

Factors That May Alter the Results of the Study

  • Drugs and other substances that may increase the overall WBC count include acetylsalicylic acid, anesthetics (chloroform, ether, isoflurane), antimicrobials (amphotericin B, chloramphenicol, erythromycin), colchicine (leukocytosis follows leukopenia), corticotropin, prednisone, and quinine.
  • Drugs and other substances that may decrease the overall WBC count include anticonvulsants, antiemetics (prochlorperazine, promethazine), antihistamines, antimalarials, antimicrobials (ampicillin, chloramphenicol, colistimethate, cycloheximide, lincomycin, penicillins, sulfa drugs, tetracycline), antineoplastics (amsacrine, busulfan, carmustine, chlorambucil, cisplatin, cyclophosphamide, cytarabine, dacarbazine, dactinomycin, mercaptopurine, methotrexate, mitomycin, procarbazine, tamoxifen), antiparasitics (pyrimethamine), antipsychotics (chlorpromazine, phenothiazine), antirheumatics (hydroxychloroquine), barbiturates, diuretics (chlorthalidone), colchicine, diazepam, dipyridamole, meprobamate, NSAIDs (dipyrone, mefenamic acid), procainamide, pyrazolone derivatives (antipyrin), quinines, radioactive compounds, ristocetin, stimulants (adrenaline, amphetamine, diethylpropion), sulfonylureas (tolazamide, tolbutamide), tolazoline, and toxins (chlordane, chlorophenothane, hexachlorobenzene, parathion).
  • Numerous drugs and other 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, cephalosporins, clindamycin, chloramphenicol, cloxacillin, dapsone, erythromycin, fluorides, gold salts, imipramine, iodides, kanamycin, mefenamic acid, methicillin, methyldopa, minocycline, nystatin, nalidixic acid, nitrofurans, procainamide, penicillin, penicillin G, ristocetin, streptokinase, streptomycin, tetracycline, triamterene, tryptophan, and viomycin.
  • Drugs and other substances that can cause a decrease in eosinophil levels include acetylsalicylic acid, amphotericin B, corticosteroids, (corticotropin, glucocorticoids, hydrocortisone, prednisone), desipramine, interferon, niacin, and procainamide.
  • A significant decrease in basophil count occurs rapidly after IV injection of anesthetics (thiopental).
  • A significant decrease in lymphocyte count occurs rapidly after administration of corticotropin, x-ray therapy, and after megadoses of niacin, pyridoxine, and thiamine.
  • Drug allergies may have a significant effect on eosinophil count and may affect the overall WBC count.
  • The WBC count may vary depending on the patient’s position, decreasing when the patient is recumbent owing to hemodilution and increasing when the patient rises owing to hemoconcentration.
  • Venous stasis can falsely elevate results; the tourniquet should not be left on the arm for longer than 60 sec.
  • The presence of nucleated RBCs or giant or clumped platelets affects the automated WBC, requiring a manual correction of the WBC count.
  • Patients with cold agglutinins or monoclonal gammopathies may have a falsely decreased WBC count as a result of cell clumping.

Other Considerations

  • Care should be taken in evaluating the CBC during the first few hours after transfusion.
  • Failure to fill the tube sufficiently (i.e., tube less than three-quarters full) may yield inadequate sample volume for automated analyzers and may be reason for specimen rejection.
  • Hemolyzed or clotted specimens 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.

Potential Medical Diagnosis: Clinical Significance of Results

Increased In

Leukocytosis

  • Normal physiological and environmental conditions:
    • Early infancy (increases are believed to be related to the physiological stress of birth and metabolic demands of rapid development)
    • Emotional stress (related to secretion of epinephrine)
    • Exposure to extreme heat or cold (related to physiological stress)
    • Pregnancy and labor (WBC counts may be modestly elevated due to increased neutrophils into the third trimester and during labor, returning to normal within a week postpartum)
    • Strenuous exercise (related to epinephrine secretion; increases are short in duration, minutes to hours)
    • Ultraviolet light (related to physiological stress and possible inflammatory response)
  • Pathological conditions:
    • Acute hemolysis, especially due to splenectomy or transfusion reactions (related to leukocyte response to remove lysed RBC fragments)
    • All types of infections (related to an inflammatory or infectious response)
    • Anemias(bone marrow disorders affecting RBC production may result in elevated WBC count)
    • Appendicitis
    • Collagen disorders (related to an inflammatory or infectious response)
    • Cushing disease(related to overproduction of cortisol, a corticosteroid, which stimulates WBC production)
    • Inflammatory disorders (related to an inflammatory or infectious response)
    • Leukemias and other malignancies (related to bone marrow disorders that result in abnormal WBC production)
    • Parasitic infestations(related to an inflammatory or infectious response)
    • Polycythemia vera (myeloproliferative bone marrow disorder causing an increase in all cell lines)

Decreased In

Leukopenia

  • Normal physiological conditions:
    • Diurnal rhythms (lowest in the morning)
  • Pathological conditions:
    • Anemias (related to WBC changes associated with nutritional deficiencies of vitamin B12 or folate, especially in megaloblastic anemias)
    • Bone marrow depression (related to decreased production)
    • Malaria (related to hypersplenism)
    • Malnutrition(related to WBC changes associated with nutritional deficiencies of vitamin B12 or folate)
    • Radiation (related to physical cell destruction due to toxic effects of radiation)
    • Rheumatoid arthritis(related to adverse effect of medications used to treat the condition)
    • Substance use disorder—alcohol (related to WBC changes associated with nutritional deficiencies of vitamin B12 or folate)
    • Systemic lupus erythematosus (SLE) and other autoimmune disorders (related to adverse effect of drugs used to treat the condition)
    • Toxic and antineoplastic drugs (related to bone marrow suppression)
    • Very low birth weight neonates(related to bone marrow activity being diverted to develop RBCs in response to hypoxia)
    • Viral infections (leukopenia, lymphocytopenia, and abnormal lymphocytes may be present in the early stages of viral infections)

Neutrophils Increased (Neutrophilia)

Neutrophils Decreased (Neutropenia)

Lymphocytes Increased (Lymphocytosis)

Lymphocytes Decreased (Lymphopenia)

Monocytes Increased (Monocytosis)

Eosinophils Increased (Eosinophilia)

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, such as interlukin-3 (IL3), interlukin-5 (IL5), granulocyte/macrophage colony-stimulating factor, and chemokines such as the eotaxins, which can result in the activation of eosinophils.

  • Addison disease (most commonly related to autoimmune destruction of adrenal glands)
  • Allergy
  • Asthma
  • Cancer
  • Dermatitis
  • Drug reactions
  • Eczema
  • Hay fever
  • Hodgkin disease
  • Hypereosinophilic syndrome (rare and idiopathic)
  • Löffler 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

Eosinophils Decreased (Eosinophilia)

  • 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)

Nursing Implications, Nursing Process, Clinical Judgement

Potential Nursing Problems: Assessment & Nursing Diagnosis

ProblemsSigns and Symptoms
Fever (related to increased basal metabolic rate, infection)Elevated temperature; flushed, warm skin; diaphoresis; skin warm to touch; tachycardia; tachypnea; seizures; convulsions
Fluid volume (deficit—related to metabolic imbalances associated with disease process, insensible fluid loss, excessive diaphoresis)Decreased urinary output, fatigue, sunken eyes, dark urine, decreased blood pressure, increased heart rate, and altered mental status
Infection (related to metabolic or endocrine dysfunction, chronic debilitating illness, cirrhosis, trauma, vectors, decreased tissue perfusion, presence of gram-positive or gram-negative organisms)Temperature, increased heart rate, increased blood pressure, shaking, chills, mottled skin, lethargy, fatigue, swelling, edema, pain, localized pressure, diaphoresis, night sweats, confusion, vomiting, nausea, headache

Before the Study: Planning and Implementation

Teaching the Patient What to Expect

  • Discuss how this test can assist in assessing for infection or monitoring conditions that affect the WBCs (e.g., leukemia).
  • Explain that a blood sample is needed for the test.

After the Study: Implementation & Evaluation Potential Nursing Actions

Treatment Considerations

Fever

  • Frequently assess and trend the temperature.
  • Ensure the patient’s immediate environment remains cool.
  • Encourage the use of light bedding and lightweight clothing to prevent overheating.
  • Increase fluid intake to offset insensible fluid loss.
  • Encourage bathing with tepid water for comfort and promotion of cooling.
  • Administer ordered antipyretics.

Fluid Volume

  • Record daily weight and monitor trends including an accurate intake and output.
  • Collaborate with HCP for administration of IV fluids to support hydration and encourage oral fluids to maximize hydration.
  • Monitor laboratory values that reflect alterations in fluid status: potassium, BUN, Cr, Ca, Hgb, and Hct.
  • Manage underlying cause of fluid loss.
  • Monitor urine characteristics and respiratory status.
  • Administer ordered replacement electrolytes.

Infection

  • Promote good hygiene and assist with hygiene when needed.
  • Administer prescribed antibiotics, antipyretics, and IV fluids.
  • Monitor vital signs and trend temperatures.
  • Adhere to standard precautions, isolate as appropriate, obtain ordered cultures, encourage use of lightweight clothing and bedding.
  • Monitor and trend indicators of infection: WBC count, CRP.
  • 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 eosinophil count to rest and take medications as prescribed, to increase fluid intake as appropriate, and to monitor temperature.

Nutritional Considerations

  • Infection, fever, sepsis, and trauma can result in an impaired nutritional status.
  • Malnutrition can occur for many reasons, including fatigue, lack of appetite, and gastrointestinal distress.
  • Carefully monitor dietary intake and facilitate the use of supplemental nutrition as appropriate to the clinical situation.
  • Adequate intake of vitamins A and C, and zinc are also important for regenerating body stores depleted by the effort exerted in fighting infections.
  • Provide information regarding the importance of following the prescribed diet including specific vitamin- or mineral-rich food sources.
  • Explain that the main dietary source of vitamin A comes from carotene, a yellow pigment noticeable in most fruits and vegetables, especially carrots, sweet potatoes, squash, apricots, cantaloupe, spinach, collards, broccoli, and cabbage.
  • Vitamin A is fairly stable at most cooking temperatures, but it is destroyed easily by exposure to light and air.
  • Explain that citrus fruits are excellent dietary sources of vitamin C.
  • Vitamin C is also found in green and red peppers, tomatoes, white potatoes, cabbage, broccoli, chard, kale, turnip greens, asparagus, berries, melons, pineapple, and guava.
  • Vitamin C is destroyed by exposure to air, light, heat, or alkalis.
  • Vegetables should be crisp and cooked as quickly as possible.
  • Boiling water before cooking eliminates dissolved oxygen that destroys vitamin C in the process of boiling.
  • Topical or oral supplementation may be ordered for patients with zinc deficiency.
  • Dietary sources high in zinc include shellfish, red meat, wheat germ, nuts, and processed foods such as canned pork and beans and canned chili.
  • Patients should be informed that phytates (from whole grains, coffee, cocoa, or tea) bind zinc and prevent it from being absorbed.
  • Decreases in zinc also can be induced by increased intake of iron, copper, or manganese.
  • Vitamin and mineral supplements with a greater than 3:1 iron/zinc ratio inhibit zinc absorption.
  • Consideration should be given to diet if food allergies are present.

Clinical Judgement

  • Consider how to emphasize the importance of completing all therapeutic management strategies to treat infection, preventing infection recidivism.

Follow-Up and Desired Outcomes

  • Acknowledges contact information provided for the U.S. Department of Agriculture’s resource for nutrition (www.choosemyplate.gov).
  • Acknowledges the correlation between an elevated WBC count and signs and symptoms of infection or allergic response.
  • Understands that other studies may be needed to confirm a diagnosis.
  • Recognizes the importance of compliance with follow-up laboratory tests to manage disease process.
  • Adheres to the request to increase fluid intake to offset fluid loss and prevent dehydration.