PPR 6340 Hematology and Coagulation

Hematology and Coagulation

• Hematology and coagulation are covered in PPR 6340 Clinical Laboratory Medicine
• Objectives include defining red blood cell indices and their interpretation, describing the coagulation cascade, defining common laboratory tests for coagulation, and understanding situations requiring specific testing for drugs.

Red Blood Cells, Hemoglobin, and Hematocrit

• Another name for a red blood cell is a "corpuscle."
• Red blood cells transport oxygen.
• Normal red blood cell counts are 4.7-6.1 x 10⁶/µL for men and 4.2-5.4 x 10⁶/µL for women.
• Hemoglobin (Hgb) is the oxygen-carrying molecule.
• Normal Hgb levels are 13.8-17.2 g/dL for men and 12.1-15.1 g/dL for women.
• Hematocrit is the percentage of red blood cells (RBCs) in the blood.
• Normal hematocrit levels are 40.7-50.3% for men and 36.1-44.3% for women.

Red Blood Cell Indices

• Mean Corpuscular Volume (MCV) estimates the average volume of a red blood cell (RBC).
• Normal MCV range is 80-96 fL.
• MCV can be calculated by dividing hematocrit by RBC count.
• Mean Corpuscular Hemoglobin (MCH) represents the average amount of hemoglobin within a red blood cell.
• Normal MCH range is 27-33 pg/cell.
• Mean Corpuscular Hemoglobin Concentration (MCHC) is the average concentration of hemoglobin in a red blood cell.
• MCHC is calculated by dividing hemoglobin by hematocrit.

Anemia

• Low hemoglobin is associated with symptoms such as weakness, fatigue, and shortness of breath.
• Reticulocyte count measures immature red blood cells, increasing in conditions like acute blood loss or hemolysis.
• A decreased reticulocyte count suggests deficiencies in iron, folate, or vitamin B12.
• Identifying the Mean Corpuscular Volume (MCV) aids in characterizing anemias
• Lower MCV indicates microcytic anemia (commonly caused by iron deficiency), while higher MCV indicates macrocytic anemia (commonly caused by folate or vitamin B12 deficiencies).

Coagulation Cascade

• The coagulation cascade describes the process of blood clotting
• The coagulation cascade has intrinsic and extrinsic pathways that converge on a common pathway.
• Key players in the pathway include factors I (fibrinogen), II (prothrombin), V, VII, VIII, IX, X, and XIII.

Activated Partial Thromboplastin Time (aPTT)

• aPTT measures factors VIII, IX, XI, and XII in the intrinsic pathway and the common pathway (factors II, V, and X).
• It is used to monitor heparin therapy and some direct thrombin inhibitors.
• Measured in seconds.
• Variability between labs is high.
• Normal range: ~30 seconds (control value).
• Historically, aPTT goal was 1.5-2.5 x control value (45-75 secs)
• aPTT needs to be established and should be consistent throughout the testing process.

Low Molecular Weight Heparins (LMWHs)

• LMWHs (e.g., enoxaparin, dalteparin) primarily inhibit factor X.
• Anti-Xa levels are used to monitor LMWHs, not aPTT.
• LMWH dosing needs to be adjusted based upon clinical status.

D-Dimer

• A breakdown product formed during clot formation.
• Used to screen for suspected blood clots, including deep vein thrombosis (DVT) and pulmonary embolism (PE).
• Normal range is typically <0.5 mcg/mL.
• Highly sensitive but nonspecific.

Prothrombin Time (PT)

• PT is a measure of factors II, V, VII, and X activity.
• Measured in seconds.
• Normal range: approximately 12 seconds (control value).
• Used to monitor warfarin therapy.

International Normalized Ratio (INR)

• INR is used to standardize PT results across different labs and reagents.
• Calculated by the lab from the International Sensitivity Index (ISI), provided by the reagent manufacturer.
• A normal INR is usually 1.
• Therapeutic ranges for INR vary by indication (e.g., common ranges 2-3).

Case Studies

• Case studies of patients with various conditions involving hematology and coagulation are discussed.