Veterinary Clinical Biochemistry and Laboratory Diagnosis

BLOOD

Blood smear

• It is essential that slides used in making smear preparations be unscratched, non-corroded and meticulously clean, free from grease, dust, acid or alkali; that slides be handled by their edges; that the blood be taken as it exudes; that the process be done rapidly so as to prevent coagulation; and that smears be left to dry in a horizontal position away from flies and dust.
• Mark necessary data with wax pencil on the end of each slide. Blood films should be stained as soon as possible after drying to ensure proper staining.
• A small drop of blood is applied to the slide approximately 20 mm from one end. A spreader (or another clean slide) is placed on the slide at an angle of 20-30^ºC and drawn back to make contact with the blood. The blood is allowed to run to each end of the spreader. The blood is spread along the slide in a fairly rapid but smooth motion.
• The blood should be pulled behind the slide and non-pushed ahead of it at an angle of less that 45^º. A thin and even blood smear should result. Wave the slide in the air until it dries (a matter of few seconds if the smear is thin enough).
• If the smear is to be stained in Giemsa’s stain, fix it by dipping in absolute methyl alcohol.
• If the smear is to be stained in Wright or Leishman’s stain, fixation is not necessary since it will take place during the staining process.
• If the smear is to be stored for more than a day or so before staining, it should be fixed in methyl alcohol. The fixed smears can be stored in slide boxes protected from dust for a period of six months.