Medical Sciences Notes on Blood Analysis and Conditions

  • Introduction to Medical Sciences

    • Topic 4: Blood

    • Overview of Full Blood Count (FBC)

  • Hematology Parameters

    • Hemoglobin (HB): Measured in g/L

    • Hematocrit (HCT)

    • Red Blood Cell (RBC) Count

    • Mean Corpuscular Volume (MCV)

    • Mean Corpuscular Hemoglobin (MCH)

    • Mean Corpuscular Hemoglobin Concentration (MCHC): Measured in g/L

    • Red Cell Distribution Width (RDW)

    • Platelet Count

    • Mean Platelet Volume (MPV)

    • White Blood Cell (WBC) Count

    • Subtypes: Neutrophils, Lymphocytes, Monocytes, Eosinophils, Basophils

  • Blood Sample Request Form

    • Personal Information:

    • Surname, Forename, Sex, Date of Birth (DoB)

    • Consultations: GP or Consultant

    • Sample Collection Details:

    • Fasting Status

    • Sample Type (Blood/Urine/CSF)

    • Time of Collection and Urgent - Yes/No

  • Key Definitions

    • Anemia: Low haemoglobin (Hb)

    • Polycythemia/Erythrocytosis: High Hb & hematocrit

    • Leukopenia: Low WBC count

    • Leucocytosis: High WBC count

    • Thrombocytopenia: Low platelet count

    • Thrombocytosis/Thrombocythaemia: High platelet count

    • Pancytopenia: Low Hb, WBCs, and platelets

  • Symptoms of Anemia

    • Fatigue (commonly referred to as "TATT")

    • Weakness

    • Pallor

    • Dizziness and Fainting

    • Shortness of Breath (SOB)

    • Chest Pain

  • Classification of Anemia

    • Microcytic: MCV LOW

    • Causes: Iron deficiency, Thalassemia

    • Normocytic: MCV NORMAL

    • Absent Reticulocytes: Aplastic anemia, Anaemia of chronic disease

    • Present Reticulocytes: Hemolysis, Sickle Cell, G6PD Deficiency

    • Macrocytic: MCV HIGH

    • Absent Megaloblasts: Myelodysplastic syndrome, Liver disease

    • Present Megaloblasts: B12 and Folate (B9) deficiencies

  • Common Treatment for Anemia

    • Address underlying cause

    • Nutritional support (diet, vitamin replacement)

    • Erythropoietin (EPO) injection

    • Blood transfusions

Polycythemia is characterized by an increased number of red blood cells in the bloodstream, leading to elevated hemoglobin and hematocrit levels. It is essential to classify polycythemia to determine its underlying causes and appropriate treatment choices.

Classification

Polycythemia is classified into two main categories:

  1. Relative Polycythemia:

    • This condition results from a decrease in plasma volume, which can falsely elevate red blood cell counts.

    • Causes may include dehydration, diuretic use, or other factors that lead to a reduction in plasma volume.

  2. Absolute Polycythemia:

    • This involves a true increase in red blood cell mass. It is further divided into two subcategories:

      • Primary Absolute Polycythemia:

      • The most well-known cause is Polycythemia Vera, which is a myeloproliferative neoplasm often associated with mutations in the JAK2 gene.

      • This condition typically leads to increased production of not just red blood cells but also white blood cells and platelets, and it can predispose individuals to thrombotic events.

      • Secondary Absolute Polycythemia:

      • This occurs as a response to external stimuli that cause increased erythropoietin (EPO) production.

      • Common causes include:

        • Renal cell carcinoma: This cancer can produce EPO, leading to increased red blood cell production.

        • Chronic hypoxia: Conditions like chronic obstructive pulmonary disease (COPD) or sleep apnea can stimulate erythropoietin synthesis due to low oxygen levels.

        • Exogenous EPO: Used as a performance-enhancing drug in athletes or in patients with certain anemias, it can lead to elevated hemoglobin levels associated with red blood cell proliferation.

The diagnosis and management of polycythemia depend on distinguishing between these classifications, and identifying underlying causes is crucial for appropriate treatment and minimizing complications such as thrombosis or hemorrhage.

  • Leukopenia Causes

    • Cancer (especially affecting bone marrow)

    • Cancer treatment (chemotherapy/radiotherapy)

    • Viral infections (e.g. HIV)

    • Autoimmune conditions

    • Low neutrophils: Neutropenia/Agranulocytosis

  • Leukocytosis

    • Causes based on WBC type:

    • Neutrophils high: Bacterial infection

    • Eosinophils high: Allergy

    • Lymphocytes high: Viral infection

  • Leukemias and Lymphomas

    • Leukemias:

    • Acute: AML (Acute Myeloid Leukemia), ALL (Acute Lymphoblastic Leukemia)

    • Chronic: CML (Chronic Myeloid Leukemia), CLL (Chronic Lymphocytic Leukemia)

    • Lymphomas:

      • Hodgkin's

      • Non-Hodgkin's (B cell, T cell)

  • Thrombocytopenia

    • Causes:

    • Decreased production from marrow (malignancies, myelodysplastic syndromes)

    • Increased platelet sequestration (e.g., splenomegaly)

    • Increased destruction (e.g., ITP, DIC, drug-related)

  • Thrombocytosis

    • Primary: Essential thrombocythemia

    • Secondary: Reactive causes (inflammation, drugs)

  • Pancytopenia

    • Causes relate to decreased production, increased destruction, or sequestration

    • Conditions include myelofibrosis, aplastic anemia

Leukopenia Causes:

  • Cancer: Especially cancers that affect the bone marrow, such as leukemias, can significantly reduce white blood cell (WBC) production.

  • Cancer Treatment: Treatments like chemotherapy and radiotherapy can suppress bone marrow activity, leading to reduced WBC counts.

  • Viral Infections: Viral infections like HIV can target and destroy specific types of white blood cells, decreasing overall WBC counts.

  • Autoimmune Conditions: In diseases where the immune system mistakenly attacks the body, like lupus, it can lead to decreased WBC levels.

  • Low Neutrophils: When neutrophil levels are low, a condition known as Neutropenia or Agranulocytosis can occur, increasing infection risk.

Leukocytosis Causes:
Leukocytosis refers to elevated WBC counts and varies based on the type of increased cells:

  • Neutrophils High: Indicates bacterial infections that cause the body to produce more neutrophils to fight the infection.

  • Eosinophils High: Often seen in allergic reactions, where eosinophils elevate as part of the immune response to allergens.

  • Lymphocytes High: Elevated levels may indicate viral infections, where the body increases lymphocyte production to combat the virus.

Leukemias and Lymphomas:

  • Leukemias are cancers of the blood-forming tissues and can be classified into:

    • Acute: Rapidly progressing conditions like Acute Myeloid Leukemia (AML) and Acute Lymphoblastic Leukemia (ALL) that require immediate intervention.

    • Chronic: These types progress more slowly and include Chronic Myeloid Leukemia (CML) and Chronic Lymphocytic Leukemia (CLL).

  • Lymphomas: Cancer of the lymphatic system includes:

    • Hodgkin's Lymphoma: Characterized by the presence of Reed-Sternberg cells.

    • Non-Hodgkin's Lymphoma: A diverse group that can arise from B or T lymphocytes with varied treatment outcomes.

Thrombocytopenia Causes:

  • Decreased Production from Marrow: Conditions like malignancies or myelodysplastic syndromes inhibit normal platelet production.

  • Increased Platelet Sequestration: Enlarged spleen (splenomegaly) can sequester more platelets, reducing their numbers in circulation.

  • Increased Destruction: Conditions like immune thrombocytopenic purpura (ITP), disseminated intravascular coagulation (DIC), or reactions to certain drugs can lead to increased destruction of platelets.

Thrombocytosis:

  • Primary: Refers to essential thrombocythemia, a disorder where the bone marrow produces too many platelets without any external cause.

  • Secondary: Also called reactive thrombocytosis, can occur in response to inflammation, infection, or side effects of certain medications.

Pancytopenia:
This condition involves depressed levels of all three blood components (red cells, white cells, and platelets). Causes include decreased production, increased destruction, or sequestration, with conditions such as myelofibrosis and aplastic anemia being notable examples.