Examination of the blood smear (differential) is an important part of the hematologic evaluation. The reliability of the information obtained depends heavily on well-made smears. Blood smears should be prepared immediately after venipuncture. Smears may also be made directly from a capillary (finger) puncture. Smears may be made from well-mixed EDTA blood, but may not be suitable for optimal interpretation.


  1. Lay the slide on a flat surface. Place a small drop of blood to the slide about 1/2 to 1 inch from one end (next to frosted portion).
  2. Place the end of a second slide (spreader slide), held with the fingertips at an angle no greater than 30 degrees, in front of the drop of blood.
  3. Pull the spreader (top) slide back into the drop of blood. When the blood has spread along 2/3 of the width of the slide, push the spreader slide forward with a steady, even motion. The angle of the spreader slide and the speed of pushing may be changed to vary the thickness of the smear. The greater the angle, the thicker the smear. Likewise, the quicker the speed, the thicker the smear.
  4. Label the slide with a lead pencil or indelible marker on the frosted end of the slide with the patient's first and last name and date of collection. Allow the smear to air dry.
  5. Prepare 4 to 6 smears for pathologist consultation or, along with bone marrow smears, for bone marrow evaluation. Place smears in slide holders for submission. Do NOT refrigerate.

    NOTE: For a bone marrow evaluation, it is requested that peripheral blood smears accompany bone marrow aspirate slides, aspirate specimen, and biopsy.
  6. Transport to WPM, along with a properly filled out WPM “SURGICAL PATHOLOGY & NON-GYN CYTOLOGY” request form requesting: [X] Peripheral Smear for Pathologist Interpretation for a peripheral smear consultation.
NOTE: Formalin/formaldehyde exposure has been shown to have a detrimental effect on peripheral blood and bone marrow smears. The vapors cause the smears to not stain adequately. Therefore, we request that peripheral blood and bone marrow smears be submitted in one specimen transport bag and the bone marrow aspirate and biopsy and/or any other specimens in formalin/formaldehyde in another, separate, specimen transport bag.

contact us

  • WPM Pathology Laboratory
  • 338 N. Front St.
  • Salina, KS 67401
  • 785.823.7201