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Red Blood Cells (Erythrocytes)
Red Blood Cells (Erythrocytes)
Routine Measurements:
Routine Measurements:
◦ Packed Cell Volume (PCV): The proportion of whole blood volume occupied by RBCs.
◦ Packed Cell Volume (PCV): The proportion of whole blood volume occupied by RBCs.
◦ Hemoglobin (Hgb) concentration: Measured from whole lysed blood.
◦ Hemoglobin (Hgb) concentration: Measured from whole lysed blood.
◦ RBC count: The number of cells per unit volume.
◦ RBC count: The number of cells per unit volume.
Calculated Parameters:
Calculated Parameters:
◦ Mean Corpuscular Volume (MCV): Varies widely by species (Goats ~15 fL; Humans ~90 fL; Birds/Reptiles ~300 fL).
◦ Mean Corpuscular Volume (MCV): Varies widely by species (Goats ~15 fL; Humans ~90 fL; Birds/Reptiles ~300 fL).
◦ Mean Corpuscular Hemoglobin Concentration (MCHC): Varies little across species, averaging ~330 g/L.
◦ Mean Corpuscular Hemoglobin Concentration (MCHC): Varies little across species, averaging ~330 g/L.
Common Artifacts:
Common Artifacts:
◦ Old samples: Causes RBC swelling (High PCV/MCV, Low MCHC).
◦ Old samples: Causes RBC swelling (High PCV/MCV, Low MCHC).
◦ Lipemia: Falsely high Hgb and MCHC.
◦ Lipemia: Falsely high Hgb and MCHC.
◦ Hemolysis: Falsely low PCV but unchanged Hgb, leading to high MCHC.
◦ Hemolysis: Falsely low PCV but unchanged Hgb, leading to high MCHC.
◦ Underfilling tubes: Causes RBC shrinkage (Low PCV/MCV, High MCHC).
◦ Underfilling tubes: Causes RBC shrinkage (Low PCV/MCV, High MCHC).
Morphological Descriptions:
Morphological Descriptions:
◦ Size: Normocytic (normal), Macrocytes (large/polychromatophilic), Microcytes (small/lack of precursors), and Anisocytosis (size variation).
◦ Size: Normocytic (normal), Macrocytes (large/polychromatophilic), Microcytes (small/lack of precursors), and Anisocytosis (size variation).
◦ Color: Normochromic (normal), Polychromasia (juvenile bluish-staining "reticulocytes"), and Hypochromasia (decreased staining, often due to iron deficiency).
◦ Color: Normochromic (normal), Polychromasia (juvenile bluish-staining "reticulocytes"), and Hypochromasia (decreased staining, often due to iron deficiency).
Clinical Conditions:
Clinical Conditions:
◦ Polycythemia (High PCV): Can be Relative (plasma shift) or Absolute (Primary/Polycythemia vera or Secondary to other disease).
◦ Polycythemia (High PCV): Can be Relative (plasma shift) or Absolute (Primary/Polycythemia vera or Secondary to other disease).
◦ Anemia (Low PCV): Classified as regenerative or nonregenerative based on causes like hemorrhage, hemolysis, or bone marrow hypoplasia.
◦ Anemia (Low PCV): Classified as regenerative or nonregenerative based on causes like hemorrhage, hemolysis, or bone marrow hypoplasia.
▪ Regenerative signs: Polychromatophilic macrocytes and normoblasts (nucleated RBCs) appear within days (except in horses).
▪ Regenerative signs: Polychromatophilic macrocytes and normoblasts (nucleated RBCs) appear within days (except in horses).
▪ AIHA (Autoimmune Hemolytic Anemia): Characterized by spherocytes (pathognomonic), where cells lose their biconcave shape.
▪ AIHA (Autoimmune Hemolytic Anemia): Characterized by spherocytes (pathognomonic), where cells lose their biconcave shape.
▪ Nonregenerative: Often secondary to renal failure (low erythropoietin), chronic infection, or bone marrow failure.
▪ Nonregenerative: Often secondary to renal failure (low erythropoietin), chronic infection, or bone marrow failure.
White Blood Cells (Leukocytes)
White Blood Cells (Leukocytes)
Interpretation Rule: Meaningful analysis requires absolute numbers rather than percentages.
Interpretation Rule: Meaningful analysis requires absolute numbers rather than percentages.
Granulocytes:
Granulocytes:
◦ Neutrophils: Phagocytes; band nuclei indicate high demand. Neutrophilia is caused by infection, stress, or steroids; Neutropenia is caused by viral infections, toxins, or marrow aplasia.
◦ Neutrophils: Phagocytes; band nuclei indicate high demand. Neutrophilia is caused by infection, stress, or steroids; Neutropenia is caused by viral infections, toxins, or marrow aplasia.
◦ Eosinophils: Inactivate histamine; increased in allergies, parasites, or mast cell tumors. Glucocorticoids cause eosinopenia.
◦ Eosinophils: Inactivate histamine; increased in allergies, parasites, or mast cell tumors. Glucocorticoids cause eosinopenia.
◦ Basophils: Rare; initiate inflammatory response via histamine release.
◦ Basophils: Rare; initiate inflammatory response via histamine release.
Agranulocytes:
Agranulocytes:
◦ Monocytes: Tissue macrophages; increased in chronic inflammation, neoplasia, or steroid responses in dogs.
◦ Monocytes: Tissue macrophages; increased in chronic inflammation, neoplasia, or steroid responses in dogs.
◦ Lymphocytes: Smallest WBCs; primary immunologic function. Lymphocytosis may indicate leukemia; Lymphopenia is often due to steroids or viral infections like parvovirus.
◦ Lymphocytes: Smallest WBCs; primary immunologic function. Lymphocytosis may indicate leukemia; Lymphopenia is often due to steroids or viral infections like parvovirus.
Platelets (Thrombocytes)
Platelets (Thrombocytes)
Function: Maintain endothelial integrity and aid in clotting.
Function: Maintain endothelial integrity and aid in clotting.
Thrombocytosis (High Count): Reaction to injury, after splenectomy, or certain treatments (vincristine).
Thrombocytosis (High Count): Reaction to injury, after splenectomy, or certain treatments (vincristine).
Thrombocytopenia (Low Count): Caused by autoimmune reactions, marrow suppression, or neoplasia.
Thrombocytopenia (Low Count): Caused by autoimmune reactions, marrow suppression, or neoplasia.
◦ Clinical Signs: Characterized by petechiae (pinpoint spots) and ecchymosis (bruising) rather than frank hemorrhage.
◦ Clinical Signs: Characterized by petechiae (pinpoint spots) and ecchymosis (bruising) rather than frank hemorrhage.
Clumping: Platelets may form "rafts" in older samples; slides must be scanned for these before reporting low numbers.
Clumping: Platelets may form "rafts" in older samples; slides must be scanned for these before reporting low numbers.
Sample Preparation and Laboratory Evaluation
Sample Preparation and Laboratory Evaluation
Collection: Use EDTA anticoagulant (purple-top) and fill the tube exactly to the mark.
Collection: Use EDTA anticoagulant (purple-top) and fill the tube exactly to the mark.
Blood Smears: Should be made immediately if analysis is delayed to prevent WBC deterioration.
Blood Smears: Should be made immediately if analysis is delayed to prevent WBC deterioration.
◦ Technique: Pull a drop of blood across a slide to create a feathered edge; air-dry quickly.
◦ Technique: Pull a drop of blood across a slide to create a feathered edge; air-dry quickly.
Evaluation Methods:
Evaluation Methods:
◦ Microhematocrit: The reference method for measuring PCV; involves spinning blood in a capillary tube for 6 minutes.
◦ Microhematocrit: The reference method for measuring PCV; involves spinning blood in a capillary tube for 6 minutes.
◦ Blood Film Examination: Essential for every patient; qualitative estimates are made for WBCs (Low to High) and Platelets (Rare to Abundant).
◦ Blood Film Examination: Essential for every patient; qualitative estimates are made for WBCs (Low to High) and Platelets (Rare to Abundant).
◦ Automated Counters: Impedance (Coulter principle) counters are standard but require technical staff. Automated differential counts are often poor for nonhuman blood and must be cross-checked with a manual film.
◦ Automated Counters: Impedance (Coulter principle) counters are standard but require technical staff. Automated differential counts are often poor for nonhuman blood and must be cross-checked with a manual film.
Analogy for Anemia Interpretation: Diagnosing anemia is like inspecting a factory assembly line. If the warehouse is empty (low PCV), you must check if there was a theft (hemorrhage), if the products were destroyed on the truck (hemolysis), or if the machinery has broken down (marrow hypoplasia).
Analogy for Anemia Interpretation: Diagnosing anemia is like inspecting a factory assembly line. If the warehouse is empty (low PCV), you must check if there was a theft (hemorrhage), if the products were destroyed on the truck (hemolysis), or if the machinery has broken down (marrow hypoplasia).
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