Many veterinarians and technicians do not routinely evaluate blood films microscopically, largely because they lack confidence in either preparing a well-made blood film or in being able to accurately identify important abnormalities. But blood films should be evaluated whenever a complete blood count (CBC) is requested, regardless of whether the CBC is done in the clinic or at a reference laboratory. Blood film evaluation is as essential to a CBC as a microscopic examination of urine sediment is to a complete urinalysis or two views are to proper radiographic interpretation. No single hematology procedure produces more valuable information yet requires so little additional time (we recommend three minutes) and expense.

Even the most expensive hematology analyzers are not designed to eliminate peripheral blood film evaluation. Morphologic features that instruments cannot identify include left shifts (increased immature neutrophils), neutrophil toxicity, lymphocyte reactivity, white blood cell (WBC) malignancy, red blood cell (RBC) poikilocytosis, RBC inclusions, and platelet abnormalities. A quick blood film review will help validate certain numerical data including platelet counts, WBC counts, WBC differentials, and RBC density, since even reference laboratory analyzers prove inaccurate with some of the more abnormal samples.

We hope this symposium will provide veterinary practitioners and technicians with the skills to properly prepare, stain, and evaluate a peripheral blood film and will encourage them to use this vital hematology tool in their practices.

Dr. Fred L. Metzger, Jr.