HEMA

• Hematology


  The study of blood
• Sample collection in clinical chemistry

  Tests are performed primarily on SERUM collected in gel barrier tubes, but the serum may also be collected in tubes with red, green, gray, or royal blue stoppers
• Samples are also performed on plasma, urine, and other body fluids
• Hematology


  • Primarily deals with the cellular elements of the peripheral blood and bone marrow
  • Includes morphologic appearance, function, and disease of blood
  • The body's main fluid for transporting nutrients, waste products, gases, and hormones through the circulatory system
• Blood composition


  • Total blood volume in an adult is 5 to 6 liters or 7 to 8% of the total body weight
  • Blood is analyzed in the form of whole blood, plasma, or serum
• Plasma


  The liquid portion of anticoagulated blood
• Serum


  The liquid portion of clotted blood

  
• Sample collection and handling

  1. Serum and plasma are obtained by centrifugation, which should be performed within 1 to 2 hours of collection

  2. Differences in the appearance or color of a specimen may adversely affect the test results
• Whole blood composition


  • Erythrocytes
  • Leukocytes
  • Platelets
  • Plasma

  
• Specimens of concern


  • Hemolyzed specimens
  • Icteric specimens
  • Lipemic specimens
• Whole blood includes erythrocytes, leukocytes, platelets, and plasma
• When a specimen is centrifuged, leukocytes and platelets make up the buffy coat (small white layer of cells lying between the packed red blood cells and the plasma)
• Plasma


  Composed of 90% water and contains proteins, enzymes, hormones, lipids, and salts
• Serum


  Normally appears clear and straw colored (lacks fibrinogen group coagulation proteins)
• 45% of blood is composed of formed elements: RBC, WBC, Platelets
• Remaining 55% of blood is fluid composed of 90% water and 10% proteins, CHO, vitamins, hormones, enzymes, lipids and salts
• Blood characteristics


  • Color: arterial blood is bright scarlet red, venous blood is dark red
  • Viscosity (resistance to flow): thick and sticky fluid that normally flows with difficulty
  • Specific gravity: 1.055 to 1.065
  • pH: 7.35 to 7.45
• Most common hematologic procedures

  • Complete Blood Count (CBC)
  • Erythrocyte Sedimentation Rate (ESR)
  • Blood Indices
  • Reticulocyte Count

  
• Specimen collection and handling

  1. Venipuncture procedure

  2. Using syringe method

  3. Using evacuated tube system

  4. Butterfly collection
• Whole blood


  • The most common body fluid analyzed in the hematology section, a mixture of cells and plasma
  • Obtained by using a collection tube with an anticoagulant to prevent clotting of the sample

  
• Most tests performed in the hematology section require blood that has been collected in tubes with a lavender stopper that contain the anticoagulant ethylenediaminetetraacetic acid (EDTA)
• Immediate inversion of the EDTA tube eight times is critical to prevent clotting and ensure accurate blood counts
• Coagulation section


  • Sometimes a part of the hematology section, but in larger laboratories it is a separate section
  • Specimen: Plasma from light blue stopper tubes (sodium citrate)
  • The overall process of hemostasis is evaluated and this includes: platelets, blood vessels, coagulation factors, fibrinolysis, inhibitors, and anticoagulant therapy (heparin and Coumadin)

  
• Routine hematology procedures


  • Complete Blood Count (CBC)
  • Erythrocyte Sedimentation Rate (ESR)
  • Reticulocyte count
  • Peripheral blood smear - morphology

  
• Reasons for specimen rejection

  • Test order requisition does not match with the identification of the patient
  • Unlabeled specimen
  • Hemolyzed sample
  • Wrong specimen collection
  • Wrong tube
  • Clotted specimen for CBC
  • Contaminated specimen
  • Lipemic sample
• Complete Blood Count (CBC)


  • Most frequent blood test
  • Provides detailed information about the cells in the blood
  • Screening test for most diseases

  
• CBC measurements


  • WBC count
  • Differential count
  • RBC count
  • Hemoglobin
  • Hematocrit
  • Blood indices
  • Platelet count
• Hematocrit


  Volume of packed red cells (VPRC)
• Microhematocrit method


  1. Fill heparinized capillary tube

  2. Seal with clay

  3. Centrifuge

  4. Read using direct reading device or caliper
• Sources of error in hematocrit count

  • Excess of anticoagulant
  • Undercentrifugation
  • Overcentrifugation
  • Improper use of reader
  • Wash out blood
  • Bubbles/spaces in the tube
• Hematocrit


  • Volume of packed RBCs that occupies a given volume of whole blood
  • Reported as percentage (%) or L/L
• Microhematocrit procedure


  1. Fill capillary tube approximately three-quarters full with anticoagulated blood

  2. Seal the end with clay and wax

  3. Centrifuge for 10,000 G for 5 minutes

  4. Determine hct using microhematocrit reader

  
• Hematocrit range: Male 40-54%, Female 35-49%, Neonates 48-68%
• Preparation of blood smear

  1. Collect before other samples to avoid platelet clumping

  2. Dermal puncture or venipuncture (EDTA within 1 hour of collection)
• Characteristics of a good blood smear

  • Smooth film of blood that covers approximately one-half to two-thirds of the slide
  • Does not contain ridges or holes
  • Has a lightly feathered edge without streaks
• Effects of technical errors in the slide

  • Uneven distribution of blood (ridges)
  • Holes in the smear
  • No feathered edge
  • Streaks in the feathered edge
  • Smear too thick and short
  • Smear too thin and long
• Peripheral blood smear (PBS) technique

  1. Wedge slide

  2. Coverslip
• PBS smear staining


  Wright's stain (eosin and methylene blue)
• Erythrocytes


  • Red blood cells
  • Anuclear biconcave disks approximately 7.2 microns in diameter
  • Contain hemoglobin to transport oxygen and carbon dioxide
  • Life span: 120 days
• Leukocytes


  • White blood cells
  • Provide immunity by producing antibodies and destroying harmful pathogens
  • Normal number: 4,500 to 11,000 per μL of blood
  • Differential cell count determines the percentage of each type