Leukocytosis Workup

Updated: May 19, 2020
  • Author: Susumu Inoue, MD; Chief Editor: Jennifer Reikes Willert, MD  more...
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Laboratory Studies

In interpreting leukocytosis on the complete blood count (CBC), consider the following:

  • Clinical features

  • Duration

  • Differential

  • Remainder of the CBC

An isolated WBC count is often ordered to minimize cost. However, most of the time, the WBC count cannot be accurately interpreted without the rest of the CBC differential. Therefore, if any question of interpretation is noted, obtain the entire CBC with differential.

Bone marrow aspiration and biopsy may be necessary to differentiate leukemia from a benign condition (leukemoid reaction), if the patient has persistent leukocytosis.

Leukocyte alkaline phosphatase (LAP) score was used to differentiate chronic myelocytic leukemia from benign leukocytosis in the past. Currently, few laboratories use this technique. Molecular determination of bcr-abl rearrangement is a more direct and specific test to make the diagnosis.