Chapter 41 Hematology

Hematologic Tests Second most common type of tests performed in POL Cellular components of blood affected by changes in organs or tissues of body

Hematologic Tests Hemoglobin Hematocrit WBC count Differential WBC count RBC count RBC indices Platelet count Erythrocyte sedimentation rate (ESR) Prothrombin time (PT)

Hematologic Tests Tests provide valuable information for diagnosis, evaluating patient’s progress, regulating further treatment

Hematologic Tests Complete blood count Hemoglobin determination Hematocrit determination RBC count (and indices) WBC count (and differential) Platelet count

Hematologic Tests Complete blood count Performed by manual testing procedures or automated hematology analyzer Results recorded in patient’s medical record Accurate and timely documentation important

Hemoglobin and Hematocrit Tests Major component of RBC Carrier of oxygen and carbon dioxide in body 85% of dry weight of RBC Synthesis of heme requires iron Adult man requires 0.5 mg/day of iron Menstruating woman requires 2 mg/day of iron

Hemoglobin and Hematocrit Tests Carries 95% of oxygen to cells Carries away 27% of carbon dioxide to lungs to be expelled Acts as blood buffer

Hemoglobin and Hematocrit Tests Frequent hemoglobin disease is anemia Measured in POL using automated device (HemoCue) Reference values vary according to both age and sex (See Procedure 41-1: Hemoglobin Determination Using a CLIA Waived Hemoglobin Analyzer)

Hemoglobin and Hematocrit Tests Packed RBC volume is ratio of volume of packed RBCs to that of whole blood specimen Cellular components of blood sample separate into layers when centrifuged at high speeds WBCs RBCs Plasma (See Procedure 41-2: Microhematocrit Determination)

Hemoglobin and Hematocrit Tests Microhematocrit Centrifuge Packed cell column showing separation of cellular components >> [FIGURES 41-5 and 41-6]

White and Red Blood Cell Counts White blood cells and differential WBCs travel to tissues of body to find and destroy pathogens Abscess: localized accumulation of pus Antibiotics are useful Normal values for WBCs vary with age

Leukocyte Identification Guide [FIGURE 41-7]

White and Red Blood Cell Counts White blood cells and differential Granulocytes: contain granules within their cytoplasm Neutrophils Basophils Eosinophils Leukocyte identified by contents of cytoplasm and shape of their nuclei Agranulocytes: do not contain granules

White and Red Blood Cell Counts White blood cells and differential Specialized protection methods Phagocytosis Detoxification Inflammation Immune response

Red Blood Cells Erythrocytes carry oxygen to body’s cells and bring back carbon dioxide Formed in bone marrow Varying sizes; round or slightly oval shape Contains hemoglobin

Platelets Platelets (thrombocytes) 140,000 to 400,000 per microliter of blood Have no nuclei Involved in clotting of blood (coagulation)

Erythrocyte Indices Mean corpuscular (cell) volume (MCV) Mean corpuscular hemoglobin (MCH) Mean corpuscular hemoglobin concentration (MCHC) Calculations that provide information about size of RBCs and hemoglobin content

Erythrocyte Indices Blood parameters: RBC count, hematocrit, hemoglobin Important in diagnosis or classification and treatment of different types of anemia

Erythrocyte Indices Using erythrocyte indices to diagnose MCH and MCV increased in megaloblastic anemias MCH and MCV increased in acute blood loss anemia, chronic hemolytic anemias, aplastic anemias, hypothyroidism, liver disease MCH and MCV decreased in hypochromic and microcytic anemias and hyperthyroidism

Erythrocyte Indices Using erythrocyte indices to diagnose MCHC increased in hereditary spherocytosis MCHC normal in macrocytosis MCHC decreased in iron deficiency anemia

Erythrocyte Sedimentation Rate Measures rate at which RBCs fall toward bottom when placed in vertical tube >> [FIGURE 41-8]

Erythrocyte Sedimentation Rate ERS or “sed rate” Used in diagnosis and treatment of many diseases Inexpensive Accurate Easy test to perform (See Procedure 41-3: Erythrocyte Sedimentation Rate)

Erythrocyte Sedimentation Rate Wintrobe method EDTA venous blood sample mixed Blood transferred with Pasteur pipette to Wintrobe tube No air bubbles Place tube vertically in rack to stand for 60 minutes Read number of millimeters red cells settled Normal values for Wintrobe method of ESR

Erythrocyte Sedimentation Rate Westergren method Mix blood sample with 3.8% sodium citrate solution before filling tube Normal values for Westergren method of ESR Sediplast ESR system

Erythrocyte Sedimentation Rate Guidelines for Wintrobe and Westergren ESR procedures to measure accurate results Erythrocytes forming rouleaux >> [FIGURE 41-10]

Erythrocyte Sedimentation Rate Using the ESR to screen ESRs increased in infections, acute stress, inflammatory diseases, tissue destruction, other conditions that lead to increase in plasma fibrinogen Increased with menstruation, pregnancy, lupus, malignant neoplasms, multiple myeloma With anemia, increases to severity of condition Decreased in polycythemia, spherocytosis, sickle cell anemia

C-Reactive Proteins CRP level rise and drop is quicker than ESR Better inflammation indicator than ESR Helps in determining systemic inflammatory conditions CRP made by liver hsCRP used in conjunction with lipid profile and cardiac risk assessment

Coagulation Studies Prothrombin time (PT) “Protime” Measures time it takes patient’s blood to clot Normal blood clots in 11-13 seconds International normalized ratio (INR) Can be universally applied (See Procedure 41-4: Prothrombin Time (Using CLIA Waived ProTime Analyzer))

Automated Hematology Advantages over manual methods: Faster Less expensive Simple to operate Accurate Instruments can be calibrated and lend themselves to control testing; most equipped with printers

Automated Hematology Can calculate part or all of RBC indices and print results Can be connected to other computers in medical facility

Automated Hematology Turn on machine and perform control testing Always follow manufacturer’s instructions [FIGURE 41-10A]