Clinical Hematology - Lecture N1

Clinical Hematology - Lecture N1

• Hematology studies the numbers and morphology of blood cells (RBCs, WBCs, and platelets) and how these results help diagnose and monitor disease.

Origin and Differentiative Stages of Circulating Blood Cells

• Pluripotent hemopoietic stem cells divide slowly, maintaining their own population and giving rise to myeloid and lymphoid progenitor cells.
• Myeloid lineage precursors (blasts) are for erythropoiesis, thrombopoiesis, granulopoiesis, and monocytopoiesis, all in the bone marrow.
• Lymphoid lineage forms B and T lymphocytes and natural killer cells in lymphoid organs.
• Erythropoietin (EPO), colony-stimulating factors (CSFs), and growth factors promote growth and differentiation.

Products and Functions of Blood Cells

• Erythrocytes: Main product is hemoglobin, main function is transporting CO₂ and O₂.
• Leukocytes (Neutrophils, Eosinophils, Basophils): Specific granules and modified lysosomes; phagocytosis of bacteria, defense against parasites, release of mediators.
• Monocytes: Granules with lysosomal enzymes; generate mononuclear phagocytes, phagocytosis, digestion.
• Lymphocytes (B and T): Immunoglobulins; kill virus-infected cells.
• Natural Killer Cells (NK): kill virus-infected and some tumor cells
• Platelets: Blood-clotting factors; clotting of blood

Composition of Whole Blood

• Whole blood consists of plasma and formed elements.
• Plasma contains amino acids, nutrients, proteins (albumins, fibrinogen, globulins), electrolytes, gases, and nitrogenous waste.
• Formed elements include platelets, leukocytes (granulocytes and agranulocytes), and erythrocytes.

Erythrocytes

• Erythrocytes, or red blood cells, are anucleated and packed with hemoglobin.
• They are biconcave disks without nuclei.
• Their shape provides a large surface-to-volume ratio, enabling efficient gas exchange.
• Human erythrocytes are typically 7.5 micrometers in diameter.

RBC Measurements

• Packed cell volume (PCV), hemoglobin concentration, and RBC count are done to measure RBCs.
• These measurements allow for calculation of Mean Corpuscular Volume (MCV) and Mean Corpuscular Hemoglobin Concentration (MCHC).

Approach to Anemia in the Adult

• Anemia is a clinical state of low red blood cell mass.
• It's defined as a reduction in the red blood cell mass.

Mechanisms of Anemia

• Three main categories of anemia: blood loss, hypoproliferative, and hemolytic anemias.
• Blood loss can be acute or chronic. Acute cases initially don't show a drop in hemoglobin due to the time needed for plasma volume restoration. Chronic blood loss eventually causes hypoproliferative anemia due to iron deficiency.

Erythropoiesis

• Erythropoiesis is the process of red blood cell production.
• Hypoxia stimulates the kidney to produce erythropoietin.
• Erythropoietin stimulates the bone marrow to produce more red blood cells.

Anemia Classification

• Categorized as absolute or relative (increased plasma volume).
• Can be acquired or hereditary.
• Can be based on red cell production or destruction.
• Includes a range of causes, e.g., mechanical damage, antibody issues, chemical injury, physical injury, membrane issues, and enzyme defects.

Reticulocyte Production

• Reticulocyte count is essential in anemia investigation.
• Modern flow cytometers measure reticulocytes using fluorescent probes.
• Normal absolute reticulocyte count is between 25,000 and 75,000 /μL.
• Absolute reticulocyte count <75,000 /μL during anemia indicates hypoproliferative processes.
• Absolute reticulocyte count > 100,000 /μL in anemia suggests hemolysis or a response to blood loss.

Mean Corpuscular Volume (MCV) and Red Blood Cell Distribution Width (RDW)

• MCV measures average red blood cell size.
• RDW measures variation in red blood cell size.
• These parameters are helpful for classifying anemia types.

More Specific Findings in Anemia

• Angular cheilitis, koilonychia, splenomegaly, cardiac murmurs, microangiopathic changes on peripheral blood smear and the presence of findings such as signs of iron deficiency.
• Splenomegaly present early in life often indicates a congenital hemolytic anemia.

Examination of the Peripheral Blood Smear

• Reviewing a properly prepared peripheral blood smear is a crucial diagnostic tool.

Bone Marrow Examination

• Bone marrow aspiration and biopsy evaluate cell morphology and bone marrow architecture.
• Used when there's diagnostic uncertainty in hypoproliferative anemia cases.
• It helps identify various disorders (e.g., myelodysplasia, leukemia, lymphoma) and certain infiltrative diseases.