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White Blood Cell Count and Differential Count
The measurement of the total and differential WBC count is part of all routine laboratory diagnostic evaluations. It is especially helpful in the evaluation of the patient with Infection, neoplasm, allergy or immunosuppression.
Noram Value WBC
Adult/child >2 years: 5000-10,000/mm³ or 5-10 × 10⁹/L (SI units)
Child ≤2 years: 6200-17,000/mm³
Newborn: 9000-30,000/mm³
Differential Count
- Neutrophils: 55-70%, 2500-8000 (Absolute per mm³)
- Lymphocytes: 20-40%, 1000-4000 (Absolute per mm³)
- Monocytes: 2-8%, 100-700 (Absolute per mm³)
- Eosinophils: 1-4, 50-500 ( Absolute per mm³)
- Basophils: 0.5-1, 25-100 (Absolute per mm³)
- WBC <2000 or >40,000/mm³
The WBC count has two components. The first is a count of the total number of WBC (leukocytes) in 1 mm³ of peripheral venous blood. The other component, the differential count, measures the percentage of each type of leukocyte present in the same specimen. An increase in the percentage of one type of leukocyte means a decrease in the percentage of another. Neutrophils and lymphocytes make up 75% to 90% of the total leukocytes. These leukocyte types can be identified easily by their morphology on a peripheral blood smear or by automated counters. The total leukocyte count has a wide range of normal values, but many diseases may induce abnormal values.
An increased total WBC count (leukocytosis, WBC count >10,000) usually indicates infection, inflammation, tissue necrosis, or leukemic neoplasia. Trauma or stress, either emotional or physical, may increase the WBC count. In some infections, especially sepsis, the WBC count may be extremely high and each levels associated with leukaemia. This is called a 'leukemoid" reaction and quickly resolves as the infection is successfully treated.
A decreased total WBC count (leukopenia; WBC count < 4000) occurs in many forms of bone marrow failure (e.g. following antineoplastic chemotherapy or radiation therapy, marrow infiltrative diseases, overwhelming infections, directly deficiencies, autoimmune diseases).
The major function of WBCs is to fight infection and react against foreign bodies or tissues. Five types of WBCcs may easily be identified on a routine blood smear. These cells, in order of frequency, include neutrophils, lymphocytes, monocytes, eosinophils, and basophils. All of these WBCs arise from the same 'pluripotent" stem cell within the bone marrow as the RBC. Beyond this origin, however, each cell line differentiates separately. Most mature WBC are then deposited into the circulating blood.
White blood cells are divided into granulocytes nongranulocytes. Granulocytes include neutrophils, basophils, and eosinophils. Because of their multilobed nuclei neutrophils are sometimes referred to as polymorphonuclear leukocytes (PMNs or 'polys'). The normal range for absolute counts depend on age, sex, and ethnicity. For example normal range for absolute neutrophils for adult African American males is 1400 to 7000 cells/ microliter.
The most common granulocyte, neutrophils, are produced in 7 to 14 days and exist in the circulation for only 6 hours. The primary function of the neutrophil is phagocytosis ( killing and digestion of bacterial microorganisms). Acute bacterial infections and trauma stimulate neutrophil production, resulting in an increased WBC count. When neutrophil production is significantly stimulated, early immature forms of neutrophils often enter the circulation. These immature forms are called band or stab cells. This occurrence, referred to as a " shift to the left" in WBC production, is indicative of an ongoing acute bacterial infection.
Basophils ( also called mast cells) and especially 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. Eosinophils and basophils do not respond to bacterial or viral infections. The cytoplasm of basophils contains heparin, histamine, and serotonin. These cells infiltrate the tissue (e.g. have in the skin) involved in the allergic reaction and serve to further the inflammatory reaction. Parasitic infestations also are capable of stimulating the production of these cells.
Nongranulocytes (mononuclear cells) include lymphocytes and monocytes ( the count also includes histiocytes). They have no cytoplasmic granules and have small, single, rounded nuclei. Lymphocytes are divided into two types: T cells 9mature in the thymus) and B cells ( mature in the bone marrow). T cells are involved primarily with cellular type immune reactions, whereas B cells participate in humoral immunity (antibody production). T cells are the killer cells, suppressor cells, and T4 helper cells. The primary function of lymphocytes to fight chronic bacterial infection and acute viral infections. The differential count does note separate the T and B cells but rather counts the combination of the two.
Monocytes are phagocytic cells capable of fighting bacteria similar to the way neutrophils do. Through phagocytosis, they remove necrotic debris and microorganisms from the blood. The monocytes produce interferon, which is the body's endogenous immunostimulant. Monocytes can be produced more rapidly, however, and can spend a longer time in the circulation then the neutrophils.
The WBC and differential count are routinely measured as part of the complete blood count. Serial WBC counts and differential counts have both diagnostic and prognostic value. For example, a persistent increase in the WBC count ( and particularly the neutrophils) may indicate worsening of an infectious process (e.g. appendicitis). A reduction in WBC count to the normal range from a previously elevated range indicates the resolution of infection. A dramatic decrease in the WBC count may contraindicate further chemotherapy.
The absolute count is calculated by multiplying the differential count (%) by the total WBC count. For example, the absolute neutrophil count (ANC) is helpful in determining the patients real risk for infection. It calculated by multiplying the WBC count by the percent of bands that is:
ANS=WBC x (% Neutrophils + Bands)
If the ANC is below 1000, the patient may need to be placed in protective isolation as he or she could be severely immunocompromised and is at great risk for infection.
Interfering Factors
- Eating, physical activity, and stress may cause an increased WBC count and alter the differential values.
- Pregnancy (final month) and labor may be associated with increased WBC levels.
- Patients who have had a splenectomy have persistent mild to moderate elevation o WBC counts.
- The WBC count lends to be lower in the morning and higher in the late afternoon.
- The WBC count tends to be age-related. Normal newborns and infants tend to have higher WBC counts than adults. It is not uncommon for the elderly to fail to respond to infection by the absence of leukocytosis. In fact, the elderly may not develop an increased WBC count even in the face of a severe bacterial infection.
- Drugs that may cause increased WBC levels include adrenaline, allopurinol, aspirin, chloroform, epinephrine, heparin, quinine, steroids.
- Drugs that may cause decreased WBC levels include antibiotics, anticonvulsants, antihistamines, antimetabolites, antithyroid drugs, arsenicals, barbiturates, chemotherapeutic agents, diuretics.
- An increased WBC count (leukocytosis) usually indicates infection, inflammation, tissue necrosis, or leukemic neoplasia.
- Serial WBC and differential counts have both diagnostic and prognostic valve. For example, a persistent increase in the WBC count may indicate a worsening of an infectious process (eg. appendicitis).
- A drastic decrease in WBC below the normal range may indicate bone marrow failure and subsequent high risk of septicemia and death.
Procedure and Patient Care
- See inside front cover for routine blood testing.
- Fasting: No
- Blood tube commonly used: lavender.
Increased WBC Count (Leukocytosis)
- Infection: WBCs are integral to initiating the body's defence mechanism against infection.
- Leukemic neoplasia or other myeloproliferative disorders: These neoplastic cells are produced by the marrow and are released into the blood stream.
- Other malignancy: Advanced non-marrow cancers (eg. lung) are associated with leukocytosis. The pathophysiology of this observation is not defined.
- Trauma, stress, or haemorrhage: The WBC count is probably under the hormonal influence (eg. epinephrine).
- Inflammation: The pathophysiology of these observations is complex, including the recognition of necrotic or normal tissue as "foreign" so that a WBC response is instituted.
- Dehydration: Not only is dehydration stress that, by itself, increases the WBC count, but also by virtue of hemoconcentration, the WBC count increases.
- Thyroid storm: The WBC count is probably influenced by thyroid hormones, marked increase in these hormones could be associated with an increased WBC count.
- Steroid use: Glucocorticocrticosteroids stimulate WBC production.
- Drug toxicity (eg. cytotoxic chemotherapy: see also drugs that decrease the WBC count).
- Bone marrow failure.
- Overwhelming infections.
- Dietary deficiency (eg. vitamin B12, iron deficiency).
- Congenital marrow aplasia.
- Autoimmune disease
- Hypersplenism.
- Lymphocyte Immunophenotyping
- Peripheral Blood Smear.
Neutrophils
Increased Levls
- Neutrophilia
- Physical or emotinal stress.
- Acute suppurative infection.
- Myelocytic leukemia.
- Trauma.
- Caushing syndrome.
- Inflammatory disorders.
- Metabolic disorders.
- Neutropenia
- Aplastic anemia
- Dietary deficiency
- Overwhelming bacterial infection
- Viral infections
- Radiation therapy
- Assison disease
- Drug therapy
Increased Levels
- Lymphocytosis
- Chronic bacterial infection
- Viral infection
- Lymphocytic leukemia
- Multiple myeloma
- Infectious mononucleosis
- Radiation
- Infectious hepatitis
- Lymphocytopenia
- Leukemia
- Sepsis
- Immunodeficiency disease
- Lupus erythematosus
- Later stages of HIV infection
- Radiation therapy
Increased Levels
- Monocytosis
- Chronic inflammatory disease
- Viral infections
- Tuberculosis
- Chronic ulcerative colitis
- Parasites
- Monocytopenia
- Apiastic anemia
- Hairy cell Leukemia
- Drug cell leukemia
- Drug therapy: prednisone
Increased levels
- Eosinophilia
- Parasitic Infections
- Allergic recations
- Eczema
- Leukemia
- Autoimmune diseases
- Eosinopenia
- Increased adrenosteroid production
Increased Levels
- Basophilia
- Myeloproliferative disease
- Leukemia
- Basopenia
- Acute allergic reactions
- Hyperthyroidism
- Stress reactions
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