RBC powerpoint

Unit 2: Hematology

Transcription Overview

  • Instructor: Scott Wilson, DVM

Erythrocytes

  • Function: Transport oxygen and carbon dioxide between lungs and tissues.

  • Hemoglobin: Protein that binds oxygen for transport.

  • Variability: Size, shape, and lifespan of erythrocytes vary between species.

    • Canine erythrocytes lifespan: 100-120 days

    • Feline erythrocytes lifespan: Approximately 70 days

    • Equine erythrocytes lifespan: 140-150 days

    • Avian erythrocytes lifespan: 28-45 days

  • Diagnostics: Analyzing erythrocytes aids in diagnosing conditions such as anemia, infections, parasitic burdens, or other hematological disorders.

Automated Analyzers

  • Purpose: Designed for veterinary hospitals to facilitate the generation of hematologic data for complete blood counts (CBCs).

  • Benefits:

    • Lower cost

    • Reduced labor investment

    • More comprehensive information

    • Reliability: Preference given to manual analysis over machine results by experienced laboratory veterinary technicians (LVTs).

Types of Cell Counts via Automated Analyzers

  • Analyzed Cells:

    • Red Blood Cells (RBCs)

    • White Blood Cells (WBCs)

    • Platelets

  • Manual Cell Count Methods: Rarely performed, except in avian and exotic practices.

Polycythemia and Anemia

  • Polycythemia:

    • Also known as erythrocytosis.

    • Increased number of RBCs

    • Accompanied by increased Packed Cell Volume (PCV) and hemoglobin concentration.

    • Types:

    • Relative polycythemia: Caused by splenic contraction or dehydration.

    • Primary polycythemia: Associated with myeloproliferative disorders.

    • Secondary polycythemia: Related to renal and lung disorders.

  • Anemia:

    • Decreased oxygen-carrying capacity of the blood.

    • Typically results from decreased numbers of circulating RBCs.

Impedance Analyzers

  • Mechanism:

    • Operates by the passage of electric current across two electrodes separated by a glass tube with a small opening (aperture).

    • Electrolyte fluid conducts the current.

    • Cells impede the flow of current due to their poor conductivity.

    • Change in current correlates with cell size.

Disadvantages of Impedance Analyzers

  • Variation in cell size can lead to inaccuracies.

  • Morphologic abnormalities may not be noted.

  • Errors in platelet and nucleated RBC counts may occur.

Quantitative Buffy Coat Analysis System

  • Function: Utilizes differential centrifugation and staining to estimate blood cells.

  • Equipment: Specialized micro-hematocrit tube.

  • Output: Provides hematocrit value and estimates of WBC and platelet concentrations.

  • Limitation: May overlook left shifts in leukocyte populations, providing only estimates.

Laser-Based Flow Cytometer Analyzers

  • Functionality: Uses focused laser beams to evaluate cell size and density based on how cells scatter light differently.

  • Application: Veterinary practice laboratories.

Combination Methods for Analyzers

  • Some systems integrate both laser-based and impedance methods (e.g., Genesis Hematology System).

Histograms from Automated Analyzers

  • Utility: Histograms can indicate anomalies in blood component distributions, particularly WBC counts.

Manual Cell Counts

  • Rarely performed in general practice, primarily utilized in avian and exotic animal practices.

  • Equipment used includes the Leukopet system and hemocytometer, allowing for precise counts of cells per microliter of blood.

Complete Blood Count (CBC)

  • Components:

    • Total RBC count

    • PCV

    • Plasma protein concentration

    • Total WBC count

    • Blood smear examination, differential WBC count, RBC and leukocyte morphology assessment

    • Reticulocyte count, especially if the patient is anemic.

    • Hemoglobin concentration

    • Erythrocyte indices

Packed Cell Volume (PCV)

  • Definition: Percentage of whole blood composed of RBCs.

  • Microhematocrit Tubes:

    • Red ring indicates heparinized tubes.

    • Blue ring indicates non-treated tubes.

  • Layers Post-Centrifugation:

    • RBC Layer: Dark-red (high specific gravity).

    • Buffy Coat: Whitish-gray layer consisting of WBCs and platelets.

    • Plasma Layer: Clear to pale yellow fluid.

  • Significance of Results:

    • Below normal: Indicates anemia or insufficient blood volume to anticoagulant ratio.

    • Above normal: Suggests polycythemia or dehydration.

Plasma Protein Concentration Measurement

  • Equipment: Plasma from hematocrit tube analyzed with a refractometer.

  • Unit: Measured in g/dL.

  • Consideration: Lipemic samples may lead to false increases in protein concentrations.

Hemoglobin Testing

  • Function: Essential component of RBCs for oxygen transport.

  • Components:

    • Heme: Contains iron.

    • Globin: Composed of amino acids.

  • Dynamics of Synthesis: Occurs during the maturation of RBCs.

  • Forms of Hemoglobin:

    • Oxyhemoglobin: Oxygen replaces CO2 during respiration.

    • Methemoglobin: Naturally occurring form within the body.

    • Sulfhemoglobin: Form generated due to cellular aging.

Erythrocyte Indices

  • Purpose: Classifies anemia and provides objective measures of RBC size and hemoglobin concentrations.

  • Accuracy Dependent On:

    • Total RBC count

    • PCV

    • Hemoglobin concentration

  • Comparative Analysis: Compare values to morphologic features to interpret results accurately.

Mean Corpuscular Volume (MCV)

  • Definition: Average size of RBCs calculated by dividing PCV by RBC concentration and multiplying by 10.

  • Example Calculation:

    • Dog with aPVC of 42% and RBC count of 6.0 million/mL:
      MCV=rac426imes10=70extfLMCV = rac{42}{6} imes 10 = 70 ext{ fL}

Mean Corpuscular Hemoglobin (MCH)

  • Measurement: Mean weight of hemoglobin in an average RBC calculated by dividing hemoglobin concentration by RBC concentration and multiplying by 10.

  • Example Calculation:

    • Hemoglobin concentration of 14 g/dL and RBC concentration of 7 million/mL:
      MCH=rac147imes10=20extpgMCH = rac{14}{7} imes 10 = 20 ext{ pg}

Mean Corpuscular Hemoglobin Concentration (MCHC)

  • Definition: Concentration of hemoglobin in the average RBC, calculated by dividing hemoglobin concentration by PCV and multiplying by 100.

  • Example Calculation:

    • Hemoglobin concentration of 14 g/dL and PVC of 42%:
      MCHC=rac1442imes100=33.3extg/dLMCHC = rac{14}{42} imes 100 = 33.3 ext{ g/dL}

Reticulocyte Counts

  • Definition: Percentage of RBCs that are reticulocytes, performed primarily on anemic patients.

  • Purpose: Assesses bone marrow's response to anemia, interpreted based on severity of anemia.

  • Reticulocyte Dynamics: In anemia, mature RBCs decrease while reticulocytes are released earlier, resulting in prolonged presence in circulation.

  • Variance: Higher percentages of reticulocytes typically correlate with hemolytic anemia compared to hemorrhagic anemia.

Calculation of Reticulocyte Counts

  • Methodology: Number of reticulocytes counted out of 1000 RBCs, expressed as a percentage.

  • Example Calculation: Count of 15 reticulocytes for a dog:
    ext{Reticulocyte ext{%}} = rac{15}{1000} imes 100 = 1.5 ext{%}

Corrected Reticulocyte Counts

  • Purpose: More accurately assess reticulocyte percentage adjusted for anemia severity.

  • Calculation Method: Observed Reticulocyte percentage multiplied by the ratio of the patient's PCV to normal PCV for that species.

  • Example Calculation:

    • Fido’s reticulocyte count = 1.5%, PCV = 25%, normal canine PCV 37-55%:
      ext{Corrected Reticulocyte} = 1.5 imes rac{25}{46} = 0.8 ext{%}

Hematologic Abnormalities

  • Hematologic abnormalities can be primary diseases or secondary to other disorders and can affect specific blood cells or all types.

  • Changes in tests of peripheral blood or bone marrow will help in diagnosing conditions.

Classifications of Abnormalities

  • Cell Number and Morphology:

    • Hypercellular: Increased cellularity.

    • Hypocellular: Decreased cellularity.

    • Aplastic: Absent cellularity.

Box 13.1: Terminology of Bone Marrow Aspiration

  • Terms and Definitions:

    • Aplasia: Less than 25% myeloid cells

    • Basophilic Hyperplasia: Basophilia in marrow and peripheral blood

    • Dyserythropoiesis: Abnormal RBC maturation

    • Dysgranulopoiesis: Abnormal granulocyte development

    • Myelodysplasia: Atypical cells with less than 30% blast calls

Inflammatory Conditions in Hematology

  • Types of Inflammatory Conditions:

    • Fibrinous: No inflammatory cells present.

    • Chronic: Increased plasma cells, mature lymphocytes, and mast cells.

    • Chronic granulomatous: Elevated macrophage counts.

Neoplasia in Hematology

  • Commonly Referred To As: Leukemia, characterized by predominance of blast cells in the bone marrow.

  • Classifications:

    • Lymphoproliferative

    • Myeloproliferative

Classification of Anemia

  • Function of RBCs: Transport and protection of hemoglobin (O2 carrier).

  • Causes of Anemia: Decreased production, increased loss, or destruction of RBCs leading to reduced oxygen capacity.

Classification Based on Bone Marrow Response

  • Regenerative Anemia:

    • Evidence of increased erythrocyte production; reticulocytes are present.

    • Typically observed with 4-7 days post-injury.

  • Nonregenerative Anemia:

    • Insufficient response from bone marrow; reticulocytes absent.

    • Common causes include Iron deficiency, Ehrlichiosis, Drug toxicity, Histoplasmosis, Renal insufficiency.

Classification by RBC Size and Hemoglobin Concentration

  • Normocytic Anemia: Normal size RBCs, often due to acute or chronic disorders.

  • Macrocytic Anemia: Larger RBCs, often transitory.

  • Microcytic Anemia: Smaller RBCs typically due to iron deficiency.

Types of Hemoglobination

  • Hypochromic: Reduced hemoglobin, common in iron deficiency.

  • Normochromic: Normal hemoglobin levels across most other types of anemia.

  • Hyperchromatic: Not typical; cells have a fixed total capacity for hemoglobin.

Box 13.2: Classification of Anemias by Erythrocyte Indices

  • Normocytic Normochromic Anemia: Conditions like hemolytic or hemorrhagic anemia if reticulocytes are absent or insufficiently responsive.

  • Macrocytic Anemia: Regenerative forms with marked reticulocytosis.

  • Microcytic Normochromic/Hypochromic Types: Chronic iron deficiency, portosystemic shunts, anemia of inflammatory disease.

Classification by Etiology

  • Types of Anemias:

    • Hemolytic: RBC destruction.

    • Hemorrhagic: Blood loss due to trauma, parasites, etc.

    • Iron Deficiency: Including nutritional or chronic blood loss.

  • Production Disorders: Includes various systemic or inherited conditions affecting erythropoiesis.

Morphologic Abnormalities of Blood Cells

  • Important to evaluate morphologic features during differential diagnosis.

  • Quantification Methods:

    • Relative percentages indicating severity using a 1+ to 4+ scale.

    • Fundamental for assessing the extent of morphologic changes.

Pelger-Huet Anomaly

  • Description: Hyposegmentation of all granulocyte nuclei, often a congenital defect.

Nuclear Hypersegmentation

  • Characterization: Neutrophils with 5 or more lobes, associated with aging.

Toxic Changes in Neutrophils

  • Indicated by basophilia, Döhle bodies, toxic granulation, and gigantism observed in conditions like infections.

Inclusions in Leukocytes

  • Presence of various pathogenic inclusions can indicate specific conditions.

Smudge Cells

  • Also known as basket cells, represent degenerative leukocytes.

Variability in Cell Arrangement and Size

  • Rouleaux & Autoagglutination: Normal in some species while pathogenic in others.

  • Anisocytosis: Variation in RBC size indicates underlying pathology.

Variation in Cell Color and Shape

  • Includes hypochromasia, normochromasia, poikilocytes, acanthocytes and others.

Inclusions in Erythrocytes

  • Identifies conditions like lead poisoning and fetal RBC remnants.

Blood Parasites

  • Include Dirofilaria, Mycoplasma, and other species' interactions.

Group Work

  • Related to chapters 8, 9, 11, 12, and 13. Blood smears will be covered in lab.