Hematology and Body Temperature Review

Hematology and Body Temperature Review

Objectives

  • Assess and interpret commonly utilized hematology tests

  • Recognize potential causes for alterations in commonly utilized hematology tests

  • Discuss common disorders of white blood cells

  • Calculate absolute number of various types of white blood cells

  • Describe temperature regulation and the pathogenesis of fever

Hematopoietic Cascade

  • Components of Hematopoiesis:

    • Myeloid Stem Cell

    • Hematopoietic Stem Cell

    • Lymphoid Stem Cell

    • Megakaryoblast

    • Proerythroblast

    • Myeloblast

    • Monoblast

    • Lymphoblast

    • Reticulocyte

    • Megakaryocyte

    • Erythrocyte

    • Basophil

    • Neutrophil

    • Eosinophil

    • Monocyte

    • End Products: Platelets, Natural Killer Cells (large granular lymphocyte), Small Lymphocyte, T Lymphocyte, B Lymphocyte

Bone Marrow

  • Characteristics:

    • Highly structured and metabolically active

    • Production:

    • 2.5 billion RBCs

    • 1 billion granulocytes/kg body weight/day

    • 2.5 billion platelets

  • Cellularity by Age:

    • Prenatal: High activity in Yolk Sac, Bone Marrow, Liver, Spleen

    • Postnatal: Activity located mainly in the marrow of ribs, femurs, tibias, vertebrae, and pelvis, with age-related decline.

Red Blood Cell (RBC) Distribution Width (RDW)

  • Definition: Measures the variation in RBC size, indicating anisocytosis.

  • Diagnostic Indicators:

    • Microcytosis: RBCs smaller than normal

    • Macrocytosis: RBCs larger than normal

  • Associated Causes:

    • Microcytic RBC:** Iron deficiency anemia, Thalassemia

    • Macrocytic RBC:** Vitamin B12 deficiency, Folate deficiency, Liver disease, Myelodysplastic syndromes (MDS), Chemotherapy

Mean Corpuscular Hemoglobin (MCH)

  • Definition: Average weight of hemoglobin in RBCs, related to oxygen-carrying capacity.

  • Presence of Hemoglobin:

    • Hyperchromic: MCH > 31 pg/cell

    • Normochromic: MCH between 27-31 pg/cell

    • Hypochromic: MCH < 27 pg/cell

Folic Acid Deficiency

  • Chemical Identity: Pteroylglutamic acid (Vitamin B9)

  • Daily Requirement: 50 mcg; 20% absorbed, synthesis by GI microorganisms.

  • Association with Anemia: Results in macrocytic megaloblastic anemia. Symptoms: weakness, fatigue, pallor.

  • Developments: Accumulation of homocysteine in vitamin B12 and folate deficiencies over weeks to months.

Iron Deficiency

  • Common Causes:

    • Poor dietary intake

    • Increased requirements during pregnancy

    • Blood loss from lesions or diseases, e.g., peptic ulcer, inflammatory bowel disease, lead poisoning

  • Symptoms: Microcytic hypochromic anemia, weakness, fatigue, palpitations, pallor, tachycardia, peculiar dietary cravings (PICA).

Assessing Anemia

  • Test for Iron Deficiency Anemia:

    • Ferritin Level - < 15 ng/mL diagnostic for iron deficiency. Level < 50 ng/mL indicates chronic inflammation.

    • Other tests include serum iron, total iron-binding capacity (TIBC), and transferrin saturation to differentiate between types of anemia.

Examples:

  • For Microcytic Anemia:

    • Iron deficiency anemia shows decreased serum iron, increased TIBC.

    • Anemia of chronic disease shows normal to increased serum iron and average TIBC.

Hemoglobinopathies

  • Sickle Cell Disease:

    • A mutation substituting valine for glutamate in the beta chain (HbS) can lead to sickling of RBCs.

    • Carrying trait: one normal, one mutated beta chain; Disease: two mutated chains.

  • Thalassemia: Deficiency in hemoglobin subunits, diagnosed through hemoglobin electrophoresis.

White Blood Cells (WBC)

  • Granulocytes:

    • Function: Phagocytosis, and destroying foreign cells. Releases enzymes post-ingestion.

    • Types: Neutrophils, Eosinophils, Basophils

  • Neutrophils: Rapid responders; levels indicative of acute infections.

  • Eosinophils: Specialize in combating parasitic infections and found in higher numbers during allergic reactions, represented in immune responses.

  • Basophils: Long-lived, involved in hypersensitivity, and increased in chronic inflammation and leukemia.

  • Monocytes: Differentiate into macrophages and dendritic cells in tissues, function as antigen-presenting cells—active in chronic infections.

Body Temperature and Fever

  • Causes of Increased Temperature:

  • Infectious: e.g., bacterial bloodstream infections

  • Non-Infectious: e.g., medications (e.g., Amoxicillin/Clavulanate), gout

  • Normal Laboratory Value Variations: Vary between labs; interpret trends in WBC and temperature carefully as they may indicate significant changes in clinical status.

  • Key Takeaway: Fluctuations in laboratory values such as MCV are important for understanding anemia and associated disorders.

Conclusion and Contact

  • For further questions, reach out to Chelsea A. Keedy, Pharm.D., or Taylor Hewitt, Pharm.D.

Contextual Notes

  • Important Definitions:

    • Microcytic Anemia: Defined by MCV < 80 fL.

    • Hypochromic Anemia: Associated with diminished hemoglobin content.

  • Connection to Disease Management: The assessment of complete blood count (CBC) can aid in diagnosing various anaemia types and establishing therapeutic management.