ISSN 2398-2993      

Blood smear interpretation

obovis

Introduction

  • It is important to be able to recognize normal features in a blood smear Blood smear: preparation, so that when examining smears from clinically unwell animals, any abnormalities can be identified .
  • This article provides information to assist veterinarians in recognizing both normal and abnormal blood smear findings.

The normal blood smear

  • A normal blood smear will have the following cells:
    • RBCs (red blood cells) which make up most of the blood smear.
    • WBCs (white blood cells):
      • Segmented neutrophils: 15-45% of the white cell count (WCC).
      • Band neutrophils: 0-2%.
      • Lymphocytes: 45-75%.
      • Monocytes: 2-7%.
      • Eosinophils: 2-20%.
      • Basophils: 0-2%.
    • Platelets.
  • The absolute count of the three cell types can be roughly estimated by blood smear examination:
    • Gross staining intensity of the slide and length of the monolayer area: severe anemia – grossly pale slide against a white background and monolayer extends farther back even to where the drop of blood was applied; normal RBC count – grossly red or orange slide and monolayer area is a small to moderate elliptical area just behind the feathered edge; high RBC count - monolayer area is small or absent.
    • Assess distribution of WBCs (even versus uneven) throughout the smears and using the 10x microscope objective subjectively estimate whether the number of WBCs per field is more or less than normal.
    • Count platelets in ten 100x oil immersion fields in the monolayer area, calculate average number of platelets/100x oil immersion field, multiply by a factor of 15,000-20,000 and the result will provide an estimate of the number of platelets/ul of blood.
  • Details on individual cell types are given below.

Erythrocytes

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Neutrophils

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Eosinophils

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Basophils

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Further Reading

Publications

Refereed Papers

  • Recent references from PubMed and VetMedResource.
  • Abramowicz B, Kurek L & Lutnicki K (2019) Haematology in the early diagnosis of cattle diseases - a review. Veterinarski Arhi 89 (4), 579-590.
  • Roland L, Drillich M & Iwersen M (2014) Haematology as a diagnostic tool in bovine medicine. J Vet Diag Invest 26 (5), 592-598 PubMed.

Other sources of information

  • Hill J, Forster J H & Mapham P H (2015) The Utility of the Blood Smear in Bovine Medicine. Vet360. Website: Vet360.
  • Harvey J W (2012) Veterinary Hematology: A Diagnostic Guide and Color Atlas. Elsevier, USA. pp 49-168. ISBN: 978-1-4377-0173-9.
  • Jones M (2011) Interpreting of Blood Work in Small Ruminants. Website: www.dvm360.com

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