Chapter 9:	Laboratory Test Data
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White Blood Cell (WBC) Count The white blood cell (WBC) count indicates how many white blood cells are found in a microliter of whole blood. Strenuous exercise, digestion of a meal, daily stress, or the presence of disease can cause the WBC count to fluctuate by as much as 2000 daily. As a diagnostic tool, WBCs are only useful when analyzed along with the patient’s overall health status and the white cell differential.

The purposes of WBC Counts are in:

• Identifying the existence of infections or inflammation.
• Determining whether further diagnostic tests (such as the WBC differential or bone marrow biopsy) are needed.
• Monitoring the patient’s response to chemo- or radiation therapy.

Values: The WBC count can range from 4100 to 10900/microliter.

Interpretation

• Elevated WBC counts generally signals the presence infection (i.e., an abscess, meningitis, appendicitis, or tonsillitis). Elevated WBCs can also be caused by leukemia and tissue necrosis caused by burns, myocardial infarction, or gangrene.

• Low WBC counts generally indicate bone marrow depression resulting from viral infections or toxic reactions.

Interfering Factors

• If the blood sample is excessively jostled or agitated it can cause hemolysis, interfering with the accuracy of the test results.

• If the patient exercises excessively, is stressed, or is digesting a meal when the count is taken, it can raise the WBC count, skewing the accuracy of the results.

• Some medications can cause the WBC to drop, resulting in inaccurate results.

White Blood Cell (WBC) Differential

The WBC differential (relative number of each type of white cell in the blood) includes information regarding white blood cell morphology and distribution. It yields more specific data regarding the immune function than the WBC count.

The purposes of the WBC differential are to:

• Evaluate immune capacity regarding infections

• Detect presence of leukemia

• Determine severity and status of infections

• Detect and evaluate allergic reactions

Values and Interpretation

Relative and absolute values are both important in evaluating the WBC differential. For example, a patient who has a seemingly high lymphocyte count might actually be well within the normal range depending on his white cell count.