Procedure for Making Blood Smears


Procedure for making Blood smears (thin films) :

  • To do a blood smear you need two slides. On one slide the blood sample is placed - this is the "sample" slide. The second slide is used to smear the drop of blood - this the "spreader" slide.
  • Clean the sample slide by wiping it with alcohol. Handle slides by edges only. (any grease on the slide will cause the dried blood to flake off during staining).
  • Place a very small drop of blood near the end of the sample slide.
  • Place the end of the spreader slide on the sample slide so that the short sided edge of the spreader is just below the drop of blood.
  • The next two steps should be done quickly to avoid smears that are too thick. Holding the spreader at an angle of 30o (relative to the sample slide), push the spreader so that the edge just barely touches the drop of blood. By capillary action, a thin line of blood will spread along the edge of the spreader .
  • Quickly drag the spreader along the entire length of the sample slide in one fluid motion. Note that the blood is being dragged by the spreader.   To view a Quick Time Video of the procedure click here.  NOTE: This is a large file and it is recommended you do not download it if you are using a modem connection.
  • If the correct amount of blood was used, and the technique was performed correctly, the smear should end before the end of the sample slide. The smear should also end in a "feathered edge" - a region where the blood cells are well separated.
  • Air dry the sample slide. Fix and stain the slide. Various methods may be used. Normally a commercial staining kit is utilized following the manufacturer's instructions.

University of Pennsylvania  2004

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