WBC differential

White Blood Cell Differential Count

• Purpose: To determine types and counts of white blood cells (WBCs) in blood.

• Procedure Overview:

  • Preparation of Blood Smear:

    • A small drop of blood is placed on a clean microscope slide.

    • Another slide is used to smear the blood drop by pulling it across the slide at a shallow angle.

    • The smearing technique aims to spread the blood thinly over the slide creating a monolayer of cells for optimal viewing.

    • After spreading, the slide is waved to speed up drying.

    • Checking for a monolayer can be done by holding the slide to light; a rainbow effect indicates a good smear worth staining.

Staining the Blood Smear

• Staining Process:

  1. Fixative Step (Alcohol): Not a stain but preserves cells on the slide to prevent washing off.

  2. Eosin Stain (Orange): Stains cytoplasmic components of certain cells.

  3. Hematoxylin Stain (Purple): Stains cell nuclei.

• Microscope Examination:

  • Ensure the slide is dry before placing it under the microscope to avoid confusion from wet slides.

Counting White Blood Cells

• Only the first 100 WBCs encountered are identified and counted to represent the overall WBC population.

• Classification of White Blood Cells:

  • Granulocytes (3 Types): Cells with granules in cytoplasm.

    • Neutrophils: Most abundant WBCs, identifiable by their segmented nuclei. Essential for fighting bacteria.

    • Band Cells: Immature neutrophils; not red blood cells or platelets.

    • Eosinophils & Basophils: Less common; eosinophils involved in allergic responses and basophils release histamine.

  • Agranulocytes (2 Types): Smaller and larger WBCs.

    • Lymphocytes: Small cells with round nuclei, involved in immune responses.

    • Monocytes: Larger with kidney-shaped nuclei; differentiate into macrophages in tissues.

• Identification Tips:

  • Granulocyte nuclei are typically segmented and may show hypersegmentation if older.

  • Lymphocytes appear round, with minimal cytoplasm, and monocytes have a significant amount of cytoplasm with distinct shapes.

Total White Blood Cell Count Calculation

• Total WBC Count: Total number of WBCs per microliter of blood.

• Absolute Neutrophil Count (ANC): Crucial for understanding immune status, especially in patients undergoing cancer treatment.

  • Calculation: Multiply total WBC count by the percentage of neutrophils found.

  • Example: If total WBC count is 10,000 and neutrophils are 55%, then ANC = 10,000 x 0.55 = 5,500 neutrophils per microliter.

• Calculating Other Cell Types:

  • Use the same method for calculating absolute counts of eosinophils, monocytes, and lymphocytes, ensuring percentages are converted correctly (e.g., 5% = 0.05).

• All absolute counts should add back to the total white blood cell count to validate accuracy.