The WBC count determines the number of leukocytes per cubic millimeter of whole blood. The counting is performed very rapidly by electronic devices. The WBC may be performed as part of a CBC, alone, or with differential WBC count. An elevated WBC count is termed leukocytosis; a decreased count, leukopenia. In addition to the normal physiological variations in WBC count, many pathological problems may result in an abnormal WBC count (see Table 1-2).

If the WBC count is low, a buffy coat smear can be performed to identify leukemia or solid tumor cells in the blood. An alteration in total WBC count indicates the degree of response to a pathological process but is not specifically diagnostic for any one disorder. A more complete evaluation is obtained through the differential WBC count.

• The normal range of WBCs for adults is 5,000 to 10,000. Variations in the WBC count across the life cycle are shown in Table 1-4 . Abnormal results may be classified by degree of severity as indicated.

• Routine screening as part of a CBC
• Suspected inflammatory or infectious process (see Table 1-2)
• Suspected leukemia, autoimmune disorder, or allergy
• Suspected bone marrow depression
• Monitoring response to stress, malnutrition, and therapy for infectious or malignant processes

Nursing Care Before the Procedure

Client preparation is the same as that for any study involving the collection of a peripheral blood sample (see Appendix I).

A venipuncture is performed and the sample collected in a lavender-topped tube. A capillary sample may be obtained in infants and children as well as in adults for whom venipuncture may not be feasible.

Because of the normal diurnal variation of WBC levels, it is important to note the time when the sample was obtained.

Nursing Care After the Procedure

Care and assessment after the procedure are the same as for any study involving the collection of a peripheral blood sample (see Appendix I).

• Abnormal test results: Provide support when diagnostic findings are revealed, especially if malignancy is a possibility or is confirmed. Reinforce information given by the physician, and answer questions or direct them to the appropriate professionals.
• Abnormal values: Note and report signs and symptoms of infection or inflammation associated with an increased count (temperature, chills), including those reflective of the site affected (pain, edema, redness, drainage). Carry out appropriate standard precautions to prevent spread to other sites. Collect a specimen for culture and sensitivities. Administer ordered antipyretic and antibiotic therapy to treat infection. Administer chemotherapeutic agents for malignancy identified and monitored by WBC and differential counts. Note and report decreased count and carry out reverse isolation procedures to protect immunosuppressed client from infection.
• Critical values: Notify the physician at once if a new client has a WBC count of less than 2,000 per microliter or greater than 50,000 per microliter or if a client whose WBC count was less than 4,000 per microliter has a change of 1,000 per microliter. Take precautions to protect the client from infection. Prepare for further diagnostic procedures to identify the cause or source of increases or decreases in the count.