A blood smear review is a cost-effective, minimally invasive, and important part of a complete blood count that can be used to identify underlying disease and illness. A systematic approach to manual blood smear review is recommended, starting with a low-magnification scan of the entire smear (to identify cellular patterns and large structures) followed by a high-magnification review of the monolayer (to assess red blood cell, white blood cell, and platelet morphology and numbers). This article describes the steps of a blood smear review with a focus on key features expected in clinically healthy dogs and cats, highlighting species- and breed-related differences to facilitate detection of clinically relevant findings.<\/p>\n
Take-Home Points<\/strong><\/p>\n <\/div><\/div><\/p>\n A complete blood count (CBC) is an important part of a minimum database, providing information on peripheral blood cells that can help identify underlying disease and illness. Hematology analyzers are commonly used to survey mammalian blood cells, and they perform relatively well for objective cellular quantifications and measurements. However, currently available in-house benchtop analyzers cannot assess morphologic changes and may be subject to interferences and misclassification of cells.1-3<\/sup> Therefore, concurrent blood smear review is recommended to verify and complement hematology analyzer findings, particularly for sick patients, for patients with flagged analyzer results, and\/or if results do not match the clinical picture.<\/span><\/p>\n A blood smear is cost-effective, minimally invasive, and relatively easy to perform and review in-house. In addition to verifying analyzer results, a blood smear can confirm a white blood cell (WBC) differential count, reveal morphologic changes of blood cells (e.g., red blood cells [RBCs],WBCs, platelets), and may facilitate detection of hemoparasites. If the results are uncertain after the review is performed, samples can be sent to a veterinary pathologist for further interpretation. In that case, when mailing a CBC blood sample to a reference laboratory, clinicians are advised to submit a freshly made blood smear along with anticoagulated blood (ideally collected less than 48 hours from laboratory receipt) to mitigate any storage-related changes that can occur with transport.<\/span><\/p>\n This article describes the steps of performing a blood smear review and highlights normal findings for dogs and cats. Knowing what to expect in healthy animals can help clinic personnel recognize abnormalities. Similar to a physical examination, the approach for a thorough blood smear review should be stepwise and the smear should be properly prepared and stained (how that can be achieved is covered elsewhere).4-7<\/sup><\/span><\/p>\n Low-magnification scans (10\u00d7 objective) help identify key divisions of a blood smear and screen for cell patterns and large structures. A blood smear can be divided into 3 parts (<\/span>FIGURES 1 AND 2<\/b><\/span>):<\/span><\/p>\n\n
Step 1: Review Entire Slide at Low Magnification<\/h2>\n
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