Hematology without the numbers: in-clinic blood film evaluation

Technical advances have made it possible for many private veterinary practices to purchase reasonably priced automated hematology instruments to perform in-clinic blood analyses. Although these instruments can quickly provide "numbers" to the clinician, evaluation of a well-made blood film can often provide information critical to the interpretation of those numbers. Blood film review is essential to identify important abnormalities such as neutrophilic left shifts and toxic change, neoplastic cells, hemoparasites, and erythrocyte morphologic changes that may suggest the cause of an anemia. Additionally, the blood film provides an important quality control measure for the automated hematology results. This article outlines a simple method of blood film evaluation, highlights the most common clinically important abnormalities, and reinforces the importance of blood film evaluation as a quality control measure.