Introduction to Hematology

Hematology Introduction

• Hematology is the study of formed cellular blood elements, including white blood cells, red blood cells, and platelets.
• Hemostasis is the process of stopping bleeding by forming a barrier to blood loss, maintaining an adequate number of cells to perform their functions.
• Hematopoiesis is the dynamic formation and development of blood cells, primarily in the bone marrow, responsible for replacing circulating blood cells.

Functions of the Hematology Lab

• Confirm a physician's clinical impression of a possible hematological disorder.
• Establish a diagnosis or rule out a diagnosis.
• Detect an unsuspected disorder.
• Monitor the effects of radiation or chemotherapy.

Blood Composition

• Plasma (55%):

  • Primarily water (92%).
  • Solutes (8%):
    • Albumins
    • Globulins
    • Fibrinogen
    • Electrolytes, hormones, vitamins, lipids, salts, enzymes, and carbohydrates.

• Functions of Plasma:

  • Transport medium for nutrients and metabolites.
  • Immune defense.
  • Coagulation.

• Cellular Elements (1%):

  • Leukocytes (White Blood Cells):
    • Granulocytes: fight infection.
    • Lymphocytes: cellular and humoral immunity.
    • Monocytes: phagocytosis of foreign substances and dead cells.
  • Platelets (Thrombocytes):
    • Help maintain hemostasis by plugging capillaries and forming clots.
    • Fragments of cytoplasm from megakaryocytes.
  • Erythrocytes (Red Blood Cells):
    • Transport oxygen to tissues.
    • Excretee carbon dioxide from tissues.
    • Do not have a nucleus within the RBCs

Cell Types on Peripheral Blood Smears

• Erythrocytes (RBCs)
• Lymphocytes
• Segmented neutrophils
• Eosinophils
• Monocytes
• Platelets
• Neutrophilic band
• Basophils

CBC Parameter affected by Hemolysis:

• WBC- Possibly unaffected
• RBC- Possibly Falsely low due to lysis or fragments
• HGB- Reportable, accurate measurement relies on RBC being completely lysed
• HCT- Falsely low, calculated with invalid MCV, and falsely low RBC.
• MCV- Falsely low or high depending on the degree of hemolysis
• MCH- Invalid, calculated with falsely low RBC count
• MCHC- Invalid, calculated with a falsely low HCT
• RDW- Falsely high due to RBC fragments
• PLT-Falsely high due to RBC fragments being incorrectly counted as platelets

Sample and Storage Requirements

• Sample: Whole blood, non-hemolyzed, avoiding clots.
• Anticoagulant: K2 or K3 EDTA.
• Storage: Room temperature for up to 1 day and up to 4°C for longer preservation, but cold may induce agglutination.

Erythrocyte and Neutrophil Changes in Aging EDTA Samples.

• Erythrocytes: Hypochromic, schistocytes, elliptocytes, spherocytes, crenated
• Neutrophils: Smudge/basket cells, cytoplasm rupture, pyknotic nuclei, loss of granulation, cytoplasmic vacuoles, loss of shape/chromatin

Observations from Aged EDTA

• Microscopic image/illustration of aged EDTA sample showing changed blood cell morphology.

Reference Ranges

• Vary according to age, race, sex, and geographic location.
• Established by individual facilities to account for patient population.

Overview of Laboratory Testing

• Complete Blood Count (CBC):
  • Measures WBC, RBC, hemoglobin, hematocrit, and platelets.
  • Calculates RBC indices.
  • WBC differential enumerates WBC types and assesses RBC morphology and platelets.
  • Indications: fatigue, weakness, infection, inflammation, bruising, bleeding.

This quiz covers the essential aspects of hematology, including the study of blood cells, hemostasis, and hematopoiesis. It also discusses the functions of the hematology lab and the composition of blood. Test your knowledge on these foundational topics in blood science.