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.
In this symposium, we suggest using a systematic method for evaluating blood films. This method--which requires veterinarians
and technicians to answer basic questions about RBC, WBC, and platelet numbers and morphology--maximizes hematologic information.
And we cover the most common and important morphologic findings in the peripheral blood.
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.