Understanding Complete Blood Count and WBCs

Oct 17, 2024

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Lecture Notes: Complete Blood Count (CBC) - White Blood Cells

Introduction

  • Lecturer: Dr. Joel
  • Topic: Complete Blood Count (CBC)
  • Importance: High, 5/5 on clinical rotations
  • Structure: Series of videos
    • Part 1: White Blood Cells
    • Part 2: Red Blood Cells
    • Part 3: Platelets and interpretation questions

What is a CBC?

  • A commonly ordered lab or blood panel
  • Provides information about cell types in blood:
    • White Blood Cells (WBCs)
    • Red Blood Cells (RBCs)
    • Platelets

Understanding CBC Columns

  1. Cell Type
  2. Sample Type: Blood vs. serum/urine/tissue
  3. Value
  4. Units
  5. Reference Range: Normal range

White Blood Cells (WBCs) Overview

  • Total WBC count is measured in cells per microliter
  • Normal range: 4.6k to 11.0k cells/μL
  • Five types of WBCs are primarily measured by percentage

Neutrophils

  • Most abundant WBCs
  • Part of the polymorphonuclear cells (neutrophils, eosinophils, basophils)
  • Function: Acute inflammation, especially bacterial infection
  • Increased Count (Neutrophilia):
    • Bacterial infections
    • Acute stress
    • Burns
    • Leukemia
    • Steroid use
    • Rheumatoid arthritis
  • Decreased Count (Neutropenia):
    • Folate or vitamin B12 deficiency
    • Aplastic anemia
    • Chemotherapy
    • Certain medications (e.g., chloramphenicol)

Eosinophils

  • Named for staining with eosin (red dye)
  • Function: Allergic reactions, parasitic infections
  • Increased Count (Eosinophilia):
    • Allergies (e.g., food allergy, bee sting)
    • Parasitic infections
    • Leukemia
    • Autoimmune disorders (e.g., polyarteritis nodosa)
  • Decreased Count (Eosinopenia):
    • Hard to define due to normal range including zero
    • Possible causes: Nutritional deficiency, glucocorticoid exposure

Basophils

  • Named for uptake of basic dyes (blue)
  • Function: Allergic responses
  • Increased Count (Basophilia):
    • Allergies
    • Chronic myelogenous leukemia
    • Blood cancers
    • Oral contraceptive pills
  • Decreased Count (Basopenia):
    • Difficult to measure (zero as lower limit)
    • Possible causes: Nutritional deficiency, glucocorticoid use

Monocytes

  • Largest WBCs
  • Function: Chronic inflammation, infection
  • Roles:
    • Phagocytosis
    • Antigen presentation
    • Cytokine production
  • Increased Count (Monocytosis):
    • Chronic inflammatory states
    • Stress response
    • Cushing's syndrome
    • Viral infections
  • Decreased Count (Monocytopenia):
    • Aplastic anemia
    • Acute myeloid leukemia (AML)
    • Glucocorticoid use
    • Myelotoxic drugs

Lymphocytes

  • Three main types: T-cells, B-cells, Natural killer cells
    • T-cells: Helper, cytotoxic, memory
    • B-cells: Plasma, memory
    • Natural Killer Cells
  • Increased Count (Lymphocytosis):
    • Viral infections
    • Leukemias
    • Adrenal insufficiency
  • Decreased Count (Lymphocytopenia):
    • HIV (targets CD4 T cells)
    • Aplastic anemia
    • Glucocorticoid use
    • Systemic lupus erythematosus
    • Rheumatoid arthritis

Conclusion

  • Part 1 focused on white blood cells
  • Encouragement to watch subsequent videos for further understanding
  • Request for feedback and comments for improvement