Leukocyte count | definition of leukocyte count by Medical dictionary

Synonym/acronym: WBC with diff, leukocyte count, white cell count.

To evaluate viral and bacterial infections and to assist in diagnosing and monitoring leukemic disorders.

Whole blood from one full lavender-top (EDTA) tube.

White blood cells (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 2–5 × 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. 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. 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 = 0.1 bands, 5/100 × 9 = 0.45 lymphs, 1/100 × 9 = 0.1 monos for a total of 9.0 WBC count. The absolute neutrophil count (ANC) for this patient would be 9 ×.92+.1) = 8.4.

The absolute neutrophil count (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 = 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 them from exposure to infectious agents. When the patient is aware of their ANC they can also make informed decisions in taking actions to avoid exposure to crowds, avoid touching things in public places that may carry germs, or avoiding 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 3–5% of total circulating neutrophils in healthy individuals. Bandemia is defined by the presence of greater than 6–10% 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 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 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 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 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.

The function of eosinophils is phagocytosis of antigen-antibody complexes. They become active in the later stages of inflammation. Eosinophils respond to allergic and parasitic diseases: They have granules that contain histamine used to kill foreign cells in the body and proteolytic enzymes that damage parasitic worms (see monograph titled “Eosinophil Count”).

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’s disease, polycythemia vera, ulcerative colitis, nephrosis, and chronic hypersensitivity states.

Problem Signs & Symptoms Interventions 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 Promote good hygiene; assist with hygiene as needed; administer prescribed antibiotics, antipyretics; provide cooling measures; administer prescribed IV fluids; monitor vital signs and trend temperatures; encourage oral fluids; adhere to standard or universal precautions; isolate as appropriate; obtain cultures as ordered; encourage use of lightweight clothing and bedding; monitor and trend indicators of infection (WBC, C-reactive protein [CRP]) Fluid volume (Related to metabolic imbalances associated with disease process; insensible fluid loss; excessive diaphoresis) Deficient: decreased urinary output, fatigue, sunken eyes, dark urine, decreased blood pressure, increased heart rate, and altered mental status Record daily weight and monitor trends; record accurate intake and output; collaborate with physician with administration of IV fluids to support hydration; monitor laboratory values that reflect alterations in fluid status (potassium, blood urea nitrogen, creatinine, calcium, hemoglobin, and hematocrit); manage underlying cause of fluid alteration; monitor urine characteristics and respiratory status; establish baseline assessment data; collaborate with physician to adjust oral and intravenous fluids to provide optimal hydration status; administer replacement electrolytes as ordered Fever (Related to increased basal metabolic rate; infection) Elevated temperature; flushed, warm skin; diaphoresis; skin warm to touch; tachycardia; tachypnea; seizures; convulsions Assess the patient’s temperature frequently; monitor for emotional labile events that could precipitate a thyroid storm or crisis and precipitate an elevation in 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 prescribed antithyroid therapy Health management (Related to failure to regulate diet; lack of exercise; alcohol use; smoking; complexity of health-care system; complexity of therapeutic management; altered metabolic process; knowledge deficit; conflicted decision making; cultural family health patterns; barriers to healthy decisions; mistrust of health-care provider [HCP]) Inability or failure to recognize or process information toward improving health and preventing illness with associated mental and physical effects; ineffective health choices; increasing symptoms of illness; verbalizes that therapeutic regime is too difficult; patient and family do not support HCP’s suggestions for health improvement; refusal to follow recommended therapeutic regime Ensure regular participation in weight-bearing exercise; assess diet, smoking, and alcohol use; teach the importance of adequate calcium intake with diet and supplements; refer to smoking cessation and alcohol treatment programs; teach the signs and symptoms of infection; assess family or cultural factors that impact the success of the therapeutic regime; assess the patient’s self-assessment of his or her health status; include the patient and family in designing the plan of care; tailor the plan of care to the patient’s lifestyle; collaborate with the patient and family to develop a system of managing own health; focus on behaviors that will make the biggest positive impact on improved health

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