Blood smear evaluation is a necessary diagnostic tool for assessing and recognizing neutrophil abnormalities. Properly interpreting morphologic abnormalities and identifying infectious agents can lead to improved patient care by enabling the clinician to recognize the early onset of inflammation and\/or disease; monitor treatment efficacy; and, in some instances, provide an immediate diagnosis. Automated hematology analyzers aid in the detection of abnormal leukocyte counts; however, manual blood smear evaluation is recommended because analyzers may not accurately classify neutrophils with certain morphologic abnormalities (e.g., left shift). In addition, accurately interpreting abnormalities of neutrophil concentration provides valuable diagnostic information and facilitates the inclusion and exclusion of a wide variety of differential diagnoses.<\/p>\n
Take-Home Points<\/strong><\/p>\n <\/div><\/div><\/p>\n Blood smear evaluation remains a critical part of a hematologic evaluation of veterinary patients, complementing the results of a CBC by enabling clinicians to identify morphologic abnormalities that may not be detected by an in-house benchtop analyzer.1-3<\/sup> This article focuses on the identification of abnormalities of peripheral blood neutrophils that may facilitate the early detection of inflammation, monitor response to treatment, and inform long-term prognosis (<\/span>BOXES 1 AND 2<\/b><\/span>). In some instances, neutrophils may contain certain infectious agents or other abnormal inclusions, and the ability to recognize these abnormalities may lead the clinician to an immediate diagnosis.<\/span><\/p>\n Cytoplasmic abnormalities<\/strong><\/p>\n Neutropenia <\/strong><\/p>\n a<\/sup>most common Neutrophils are the first immune cells to respond to inflammation and infection and are derived from myeloid (granulocytic) precursors in the bone marrow. Granulocytic precursors exhibit pyramidal maturation progressing from the earliest precursors, myeloblasts, to progranulocytes; myelocytes; metamyelocytes; band cells; and, lastly, mature, segmented neutrophils. The stages can be distinguished by their nuclear and cytoplasmic features.<\/span><\/p>\n Figure 1A. Myeloblast in bone marrow aspirate from a dog. Myeloblasts are uncommonly encountered in peripheral blood, and their presence raises concern for myeloid leukemia; however, myeloblasts may also be seen with severe inflammation as a part of left shift. Wright-Giemsa stain, 100\u00d7 objective.<\/p><\/div><\/li>\n Figure 1B. Progranulocyte in canine blood. Wright-Giemsa stain, 100\u00d7 objective.<\/p><\/div><\/li>\n Figure 1C. Neutrophilic myelocyte in canine blood. Wright-Giemsa stain, 100\u00d7 objective.<\/p><\/div><\/li>\n Figure 1D. Neutrophilic metamyelocyte in canine blood. Wright-Giemsa stain, 100\u00d7 objective.<\/p><\/div><\/li>\n Figure 1E. Band cell in canine blood. Wright-Giemsa stain, 100\u00d7 objective.<\/p><\/div><\/li>\n\n
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\nb<\/sup>less common in dogs<\/div><\/div>\nNeutrophil Maturation and Normal Morphology<\/h2>\n
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<\/a><\/a><\/a><\/a><\/a>Figure 2A. Normal neutrophil in canine blood. Wright-Giemsa stain, 100\u00d7 objective.<\/span><\/a><\/div><\/div>