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Leukocytosis Workup

  • Author: Susumu Inoue, MD; Chief Editor: Robert J Arceci, MD, PhD  more...
Updated: Jul 10, 2015

Laboratory Studies

In interpreting leukocytosis on the CBC count, consider the following:

  • Clinical features
  • Duration
  • Differential
  • Remainder of the CBC count

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 count 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.

Contributor Information and Disclosures

Susumu Inoue, MD Professor of Pediatrics and Human Development, Michigan State University College of Human Medicine; Clinical Professor of Pediatrics, Wayne State University School of Medicine; Director of Pediatric Hematology/Oncology, Associate Director of Pediatric Education, Department of Pediatrics, Hurley Medical Center

Susumu Inoue, MD is a member of the following medical societies: American Academy of Pediatrics, American Society of Clinical Oncology, American Society of Hematology, American Society of Pediatric Hematology/Oncology, Society for Pediatric Research

Disclosure: Nothing to disclose.

Specialty Editor Board

Mary L Windle, PharmD Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Nothing to disclose.

Gary D Crouch, MD Associate Professor, Program Director of Pediatric Hematology-Oncology Fellowship, Department of Pediatrics, Uniformed Services University of the Health Sciences

Gary D Crouch, MD is a member of the following medical societies: American Academy of Pediatrics, American Society of Hematology

Disclosure: Nothing to disclose.

Chief Editor

Robert J Arceci, MD, PhD Director, Children’s Center for Cancer and Blood Disorders, Department of Hematology/Oncology, Co-Director of the Ron Matricaria Institute of Molecular Medicine, Phoenix Children’s Hospital; Editor-in-Chief, Pediatric Blood and Cancer; Professor, Department of Child Health, University of Arizona College of Medicine

Robert J Arceci, MD, PhD is a member of the following medical societies: American Association for the Advancement of Science, American Association for Cancer Research, American Pediatric Society, American Society of Hematology, American Society of Pediatric Hematology/Oncology

Disclosure: Nothing to disclose.


Gary R Jones, MD Associate Medical Director, Clinical Development, Berlex Laboratories

Gary R Jones, MD is a member of the following medical societies: American Academy of Pediatrics, American Society of Pediatric Hematology/Oncology, and Western Society for Pediatric Research

Disclosure: Nothing to disclose.

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WBC counts.
Table. Normal Leukocyte Counts
    Total Leukocytes*   Lymphocytes   Neutrophils   Monocytes   Eosinophils
Age   Mean Range   Mean Range %   Mean Range %   Mean %   Mean %
Birth   ... ...   4.2 2-7.3 ...   4 2-6 ...   0.6 ...   0.1 ...
12 h   ... ...   4.2 2-7.3 ...   11 7.8-14.5 ...   0.6 ...   0.1 ...
24 h   ... ...   4.2 2-7.3 ...   9 7-12 ...   0.6 ...   0.1 ...
1-4 wk   ... ...   5.6 2.9-9.1 ...   3.6 1.8-5.4 ...   0.7 ...   0.2 ...
6 mo   11.9 6-17.5   7.3 4-13.5 61   3.8 1-8.5 32   0.6 5   0.3 3
1 y   11.4 6-17.5   7.0 4-10.5 61   3.5 1.5-8.5 31   0.6 5   0.3 3
2 y   10.6 6-17   6.3 3-9.5 59   3.5 1.5-8.5 33   0.5 5   0.3 3
4 y   9.1 5.5-15.5   4.5 2-8 50   3.8 1.5-8.5 42   0.5 5   0.3 3
6 y   8.5 5-14.5   3.5 1.5-7 42   4.3 1.5-8 51   0.4 5   0.2 3
8 y   8.3 4.5-13.5   3.3 1.5-6.8 39   4.4 1.5-8 53   0.4 4   0.2 2
10 y   8.1 4.5-13.5   3.1 1.5-6.5 38   4.4 1.8-8 54   0.4 4   0.2 2
16 y   7.8 4.5-13   2.8 1.2-5.2 35   4.4 1.8-8 57   0.4 5   0.2 3
21 y   7.4 4.5-11   2.5 1-4.8 34   4.4 1.8-7.7 59   0.3 4   0.2 3

* Numbers of leukocytes are in X 109 \L or thousands per μ L; ranges are estimates of 95% confidence limits; and percentages refer to differential counts.

Neutrophils include band cells at all ages and a small number of metamyelocytes and myelocytes in the first few days of life.

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