White Blood Cell Count and Differential

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Latest Edit: Hector 2014-03-21 (EDT)

See Also Lab Tests

A white blood cell count and differential is part of the complete blood count. It is helpful in the evaluation of infection, allergy, neoplasm or immunosuppression.[1], [2]


The white blood cell count and differential is a measure of the total number of white blood cells and it measures the percentage of each type of leukocyte present in the blood. The different leukocytes include:

Patient Preparation

  • Fasting is not required for this test.

Interfering Factors:

  • Eating, physical activity and stress may increase the WBC count and alter the differential values.
  • Pregnancy in the final month and labor may increase the WBC level.
  • WBC count tends to be lower in the morning and higher in the late afternoon.
  • Newborns tend to have higher normal WBC counts, whereas the elderly often have lower WBC counts even when faced with an infection.
  • Drugs that may caused increased WBC levels include adrenaline, allopurinol, aspirin, chloroform, epinephrine, heparin, quinine, steroids, an triamterene.
  • Drugs that may cause decreased WBC levels include antibiotics, anticonvulsants, antihistamines, antimetabolites, antithyroid]] drugs, arsenicals, barbituates, chemotherapeutic agents, diuretics, and sulfonamides.

Clinical Implications

A WBC is typically used to assess for or monitor infection, inflammation, necrosis or leukemic neoplasia. Other indications include:

High levels (referred to as leukocytosis) indicates:

Low levels (referred to as leukopenia) indicates:

  • chronic or overwhelming infections
  • dietary deficiencies
  • drug toxicity
  • congenital marrow aplasia
  • bone marrow infiltration
  • autoimmune disease
  • hyperspenism

Associated Tests

The following white blood cell differentials are typically included: neutrophils, lymphocytes, monocytes, eosinophils and basophils. Other tests associated with a WBC count include lymphocyte immunophenotyping and peripheral blood smear.


  1. Pagana Kathleen D, Pagana Timothy J (2006) Mosby's Manual of Diagnostic and Laboratory Tests, Mosby.
  2. Weatherby Dicken, Ferguson Scott (2002) Blood Chemistry and CBC Analysis: Clinical Laboratory Testing from a Functional Perspective, Bear Mountain.