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https://en.wikipedia.org/wiki/White_blood_cell

White Blood Cell Count

• Normal range (4.0-11.0 x 10³ cells/mm³)
• 2 Parts
  • Actual count of the number of leukocytes in one cubic millimeter of blood
  • Differential count (% of each of the 5 types of leukocytes)
• < 4.0 x 10³ cells/mm³ = leukopenia
  • Bone marrow failure, blood malignancies, infections
• > 11.0 x 10³ cells/mm³ = leukocytosis
  • Infections, inflammation, blood malignancies
• Differential
  • Granulocytes
    • Neutrophils (45-73%)
      • Bands (3-5%)
      • “Left shift”
      • Absolute Neutrophil Count (ANC)
        • (%PMN + %Bands) x WBC / 100
        • < 1500 = neutropenia
    • Eosinophils (0-4%)
    • Basophils (0-1%)
  • Non-granulocytes
    • Lymphocytes (20-40%)
      • 3 Main Types
        • T-Cells = cell mediated immunity
        • B-Cells = humoral immunity (immunoglobulins)
        • Natural Killer Cells (NKC)
    • Monocytes (2-8%)

Red Blood Cell Count

• Actual count of RBC in one cubic millimeter of blood
  • Normal range
    • Male (4.5-5.9 x 10¹² cells/L)
    • Female (4.1-5.1 x 10¹² cells/L)
  • Reasons for gender differences in RBC markers
    • Blood loss from menstruation
    • Testosterone is hematapoetic
  • 2 main markers
    • Hemoglobin
      • Amount of Hgb contained in a given volume of blood
      • Normal Range
        • Male (14-17.5 g/dL)
        • Female (12.3-15.3 g/dL)
    • Hematocrit
      • % of total blood volume made up by RBC
      • Normal range
        • Male (42-50%)
        • Female (36-45%)
      • As a general rule of thumb, most agreed upon transfusion trigger is Hgb < 7.0 g/dL and/or Hct < 20%

Red Blood Indices

• Essentially assess the size and hemoglobin content of the RBC and is useful in the evaluation of anemias, polycythemias, and nutritional deficiencies
• Mean Corpuscular Volume (MCV)
  • Average size of the volume of RBC (Hct/RBC count)
  • Normal range (80-100 fL/cell)
    • < 80 = Microcytic
    • > 100 = Macrocytic
• Mean Corpuscular Hemoglobin (MCH)
  • Average amount of hemoglobin within a RBC
  • Closely resembles MCV and of little clinical use
• Mean Corpuscular Hemoglobin Concentration (MCHC)
  • Calculation of Hgb/Hct
  • Normal range (32-36 g/dL)
    • < 32 = hypochromic
    • > 36 = hyperchromic
• Red Blood Cell Distribution Width (RDW)
  • Indication of RBC size variability (degree of anisocytosis)
  • Normal range (11-14%)
• Reticulocyte Count
  • Measure of immature RBC in circulation
    • Evaluates bone marrow function and erythropoetic activity
  • Normal range (0.5-2.5%)
  • Reticulocyte Index
    • Measures whether this response is appropriate
    • Reticulocyte Count % x (Patient’s Hct/Normal Hct)
      • < 1.0 = poor response

Platelet Count

• Actual count of thrombocytes in one cubic millimeter of blood
• Normal range (150,000-450,000/µL)
• Mean Platelet Volume (MPV)
  • Relationship between size and count
  • Immature platelets are larger
  • MPV is analogous to the MCV

Strategies for Quick Interpretation

• If abnormal WBC:
  • Correlate with clinical picture
    • An abnormal number may be a normal response to illness or a marker of illness severity
  • Look at your differential
  • If leukopenic, then calculate ANC
• If abnormal RBC:
  • Is your patient symptomatic?
  • Look at your indices
  • Calculate reticulocyte count for response
• If abnormal platelet:
  • Is the patient bleeding?

Fishbone diagram for CBC with differential

References

1) Pagana KD, Pagana TJ.  Mosby’s Manual of Diagnostic and Laboratory Tests.  5^th ed.  St. Louis, MO. Elsevier. 2014.

2) Lee M.  Basic Skills in Interpreting Laboratory Data.  5^th ed.  Bethesda, MD.  American Society of Health-Systems Pharmacists.  2013

3) Laposata M.  Laboratory Medicine: The Diagnosis of Disease in the Clinical Laboratory.  2^nd ed.  New York, NY.  2014.