Blood Smear and Complete Blood Count Quiz

Blood Smear

• A blood smear is created by spreading a drop of peripheral blood on a slide.
• Examined microscopically.
• Procedure used to obtain a WBC count, differential count, estimate platelet count, and evaluate RBC morphology.

Complete Blood Count

• Hemoglobin, hematocrit, RBC count, WBC count, mean cell volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC) make up a complete blood count.
• Hemoglobin: measures the oxygen-carrying capacity of red blood cells.
• Hematocrit: measures the percentage of red blood cells in the blood.
• RBC Count: measures the number of red blood cells per volume of blood.
• WBC Count: measures the number of white blood cells per volume of blood.
• MCV: measures the average size of red blood cells.
• MCH: measures the average amount of hemoglobin in red blood cells.
• MCHC: measures the average concentration of hemoglobin in red blood cells.

Coagulation Tests

• Bleeding Time: A test that assesses the time it takes for bleeding to stop after a standardized skin incision is made, evaluating platelet quantity and function.
• Activated Partial Thromboplastin Time (aPTT): assesses the intrinsic clotting pathway (all clotting factors except VII).
• Prothrombin Time (PT): assesses the extrinsic and common clotting pathway.

Direct Coombs' Test

• A positive direct Coomb's test result indicates that an immune mechanism is attacking the patient's own red blood cells.
• Used to detect hemolytic anemia, lupus, and drug-induced hemolysis, such as caused by methyldopa, penicillin, and quinidine.

Indirect Coombs' Test

• Used for prenatal testing of pregnant women and in testing blood prior to a blood transfusion.

Crossmatching

• Determines compatibility between donor and recipient blood.
• Agglutination between the donor's red blood cells and the recipient's serum indicates incompatibility.

Hemoglobin Electrophoresis

• Uses electrophoretic separation and immunodiffusion to screen for abnormalities such as multiple myeloma.

Red Blood Cell Appearance

• Acanthocytes (Spur Cells): Red blood cells with long, thin, irregularly placed spikes on the membrane associated with alcoholic cirrhosis and heparin therapy.
• Echinocytes (Burr Cells): Red blood cells with evenly distributed spicules on the membrane associated with uremia and hyperlipidemia.
• Schistocytes: Fragmented red blood cells.
• Spherocytes: Small round red blood cells associated with iron deficiency anemia.
• Stomatocytes: Red blood cells with central slit-like areas of pallor.
• Target Cells: Red blood cells appear pale with a dark central area.
• Elliptocytes: Rod-shaped red blood cells associated with sickle cell trait and thalassemia.
• Ovalocytes: Oval-shaped red blood cells associated with microcytic and megaloblastic anemia.
• Macrocytes: Larger than normal red blood cells.
• Microcytes: Smaller than normal red blood cells.
• Normocytes: Normal sized red blood cells.
• Anisocytosis: Unequal size of red blood cells.
• Hypochromia: Decrease in the hemoglobin content of red blood cells.
• Normochromia: Normal red blood cell color.

White Blood Cells

• Granulocytes: Include basophils, eosinophils, and neutrophils.
• Lymphocytes: Provide humoral, cell-mediated, and cytotoxic immune responses.
• Monocytes: Macrophage precursors.

Basophils

• Produce heparin.
• Increased during chronic hypersensitivity states and myeloproliferative diseases.

Eosinophils

• Contain numerous inflammatory mediators.
• Increased during parasitic infections and allergic reaction.
• May also increase in some neoplastic disease, skin disorders, and collagen vascular diseases.

Neutrophils

• Also known as polymorphonuclear cells.
• Phagocytic cells that engulf and destroy bacteria.
• Increased during infection, tissue necrosis, inflammatory disease, metabolic disorders, and some leukemias.

T lymphocytes

• Derived from the thymus.
• Responsible for cell-mediated immunity.
• Activate phagocytes, antigen-specific cytotoxic T-lymphocytes, and release cytokines in response to an antigen.
• CD4+ (Helper T cells): Further divided into Th1, Th2, Th17, and iTreg cells involved in various immune responses.
• CD8+: Increased in hepatitis B, acute mononucleosis, and cytomegalo infection.

B lymphocytes

• Derived from the bone marrow.
• Responsible for humoral immunity and produce antibodies.
• Increased during viral disease, bacterial disease, metabolic disease, and chronic inflammatory conditions.
• Decreased during immunodeficiency syndromes, severe illness, and diseases associated with abnormalities of the lymphatic circulatory system.

Null lymphocytes

• Neither T-cell nor B-cell lymphocytes.

Monocytes

• Increased during infection, granulomatous, and collagen vascular disease.
• AKA macrophages

Platelets

• Initiate hemostasis.
• Normal value: 150-400 cells/mm3.
• Platelet function is impaired by aspirin, dipyridamole, NSAIDs, uremia, multiple myeloma, and severe liver disease.
• Conditions with thrombocytopenia include bone marrow dysfunction, aplastic anemia, leukemia, viral infections, peripheral platelet destruction, idiopathic thrombocytopenic purpura, disseminated intravascular coagulation, and hemolytic uremic syndrome.

Carboxyhemoglobin (COHb)

• A compound formed by carbon monoxide and hemoglobin.
• Displaces oxygen in red blood cells.
• Normal COHb level for non-smokers is up to 3%.
• For smokers, 10-15% is normal.

Blood Lab Tests By Cell Type

• Red Blood Cells: Carboxyhemoglobin
• White Blood Cells: Basophils, Eosinophils, Neutrophils, T lymphocytes (CD4+ and CD8+), B lymphocytes, Null lymphocytes, and Monocytes
• Platelets: