Leukocytosis

Basics

Description

Definition:
  • Any elevation of total number of white blood cells (WBCs) beyond expected value
  • Normal range for total WBCs (/mm3):
    • Adults: 4,500–11,000
    • Children: WBC count decreases with age:
      • Infant, 1 wk old: 5,000–21,000
      • Toddler, 1 yr old: 6,000–17,500
      • Child, 4 yr old: 5,500–15,500
    • Pregnancy:
      • First trimester: 5,000–14,000
      • Second trimester: 5,000–15,000
      • Third trimester: 5,000–17,000
  • Normal ranges shift upward with:
    • Exercise
    • Female gender
    • Smoking
    • Daytime hours
  • Given wide range of normal values, numbers must be interpreted in clinical context
  • Specific subsets
  • Neutrophil predominance (neutrophilia):
    • Absolute neutrophil count >7,500/mm3
    • Half of circulating neutrophils are adherent to blood vessel walls. They can be rapidly released (demarginate) in response to acute stressors. This can double the WBC count
    • An additional pool of mature neutrophils, immature metamyelocytes, and band neutrophils are stored in the bone marrow. These can be released, increasing the neutrophil count, typically during inflammation or infection. Release of immature forms results in a “left shift”
  • Lymphocyte predominance (lymphocytosis):
    • Absolute lymphocyte count >4,000/mm3
    • Stored in the spleen, lymph nodes, thymus, and bone marrow. They are typically released in response to foreign antigens or viral infections
  • Hyperleukocytosis (WBC >100,000/mm3):
    • Seen primarily in hematologic malignancies
    • Associated with leukostasis, which can lead to cerebral infarction, pulmonary insufficiency, death

Epidemiology

  • CBC most common test ordered from the ED
  • Leukocytosis is one of the most commonly found lab abnormalities
  • Elevated WBC count can be found in 17% of ED patients in whom a CBC is checked

Etiology

  • Neutrophilia:
    • Demargination/stress reaction:
      • Stress
      • Exercise
      • Surgery
      • Seizures
      • Trauma
      • Hypoxia
      • Pain
      • Vomiting
    • Inflammation:
      • Rheumatoid arthritis
      • Gout
      • Inflammatory bowel disease
      • Vasculitis
    • Infection, generally bacterial
    • Lab error
    • Labor
    • Leukemoid reaction (TB, Hodgkin, sepsis, metastasis)
    • Medications:
      • β-agonist (epinephrine, cocaine, parenteral albuterol)
      • Corticosteroids
      • Lithium
      • Granulocyte colony stimulating factor
    • Metabolic disorders:
      • DKA
      • Thyrotoxicosis
      • Uremia
    • Malignancy, nonhematogenous
    • Myeloproliferative disorders:
      • Chronic myeloid leukemia
      • Polycythemia vera
    • Pregnancy
    • Rapid RBC turnover:
      • Hemorrhage
      • Hemolysis
    • Smoking
    • Tissue necrosis:
      • Cancer
      • Burns
      • Infarction
  • Lymphocytosis:
    • Infection, generally viral, early stages:
      • Infectious mononucleosis
      • VZV
      • CMV
      • Viral hepatitis
    • Bacterial infection, specifically:
      • Pertussis
      • TB
      • Syphilis
      • Rickettsia
      • Babesia
      • Bartonella
    • Hypothyroidism
    • Immunologic responses:
      • Immunization
      • Autoimmune diseases
      • Graft rejection
    • Lymphoproliferative disease:
      • Acute lymphocytic leukemia
      • Chronic lymphocytic leukemia
      • Non-Hodgkin lymphoma
    • Splenectomy
  • Monocytosis:
    • Infection:
      • EBV
      • Fungal
      • Protozoa
    • Autoimmune/rheumatologic disorders
    • Splenectomy
  • Eosinophilia:
    • Infection, primarily parasitic and fungal
    • Allergic disorders
      • Allergic rhinitis
      • Asthma
      • Drug reaction/hypersensitivity
    • Hematologic malignancy
    • Connective tissue disease
  • Basophilia:
    • Allergic disorders
    • Hematologic malignancy

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