PBS & WBC DIFFERENTIAL

• Peripheral blood film


  Examination of the peripheral blood and correlation with the complete blood count
• Sources of blood specimens

  • Tripotassium ethylenediaminetetraacetic acid (EDTA) tubes
  • Finger and heel punctures
• Blood films from EDTA tubes

  • Unacceptable blood cell artifacts if left at room temperature for more than 5 hours: echinocyte red blood cells, spherocytes, necrobiotic leukocytes, vacuolated neutrophils
• Vacuolization of monocytes


  Normally occurs almost immediately with EDTA but causes no evaluation problems
• Advantages of making films from blood in EDTA tube

  • Multiple slides can be made if necessary and they do not have to be prepared immediately after the blood is drawn
  • EDTA generally prevents platelets from clumping on the glass slide, which makes the platelet estimate more accurate during film evaluation
• Pseudo leukocytosis


  Occurs when platelet agglutination are similar in size to WBCs and automated analyzers cannot distinguish the two, so the platelet clumps are counted as WBCs instead of platelets
• Peripheral film preparation


  1. Manual wedge technique

  2. Automated slide making and staining
• Drying of films


  All blood films and bone marrow smears should be dried as quickly as possible to avoid drying artifact
• Blowing breath on a slide

  Causes RBCs to become echinocytic (crenated) and develop water artifact (also called drying artifact)
• Staining of peripheral blood films

  Pure Wright stain or a Wright-Giemsa stain (Romanowsky stain) is used<|>Methanol in the stain fixes the cells to the slide<|>Oxidized methylene blue and eosin form a thiazine-eosinate complex, which stains neutral components<|>Free methylene blue stains acidic (and basophilic) cellular components, such as ribonucleic acid (RNA)<|>Free eosin stains basic (and eosinophilic) components, such as hemoglobin and eosinophilic granules<|>Neutrophils have cytoplasmic granules that have a neutral pH and pick up some staining characteristics from both stains
• Water or drying artifact appearances

  Heavily demarcated central pallor, refractive (shiny) blotches on the RBCs, echinocytes (crenation)