Leukocyte Total and Differential Count Lab 5

WBC TOTAL COUNT Can be determined: manually by haemocytometer and microscope automated by haematological analysers by estimation from a blood smear -100x magnification Mean of 10 fields x 100 = WBC x 109/L -400x magnification Mean of 10 fields x 1,500 = WBC x 109/L

-Leukocyte estimation in a blood smear (400x): Normal number Increased Decreased

DIFFERENTIAL LEUKOCYTE COUNT Can be determined: from a stained blood smear automated by some haematological analysers, but these need prior validation

DIFFERENTIAL COUNT IN A STAINED BLOOD SMEAR: BATTLESHIP METHOD

How to perfom a differential count: Count 100-200 leukocytes, note each cellular type identified Avoid counting the same field twice Do not focus on one section of the smear

TYPES OF LEUKOCYTES GRANULOCYTES: Neutrophils, Eosinophils, Basophils MONOCYTES - LYMPHOCYTES

Normal neutrophils and a lymphocyte Neutrophils are similar in most domestic species, characterised by pale cytoplasm and dark nucleus segmented into 2-5 lobes, although granules are more readily seen in ruminants.

Small and medium lymphocyte, cow Small lymphocytes, dog

Normal neutrophil and monocyte Monocytes are similar in most species; large cells with basophilic cytoplasm (often vacuolated or with tiny pink granules), and a pale irregularly clefted or folded nucleus with clumped chromatin.

Normal eosinophil and basophil Morphology of eosinophils varies widely with species; granules are large in horses, small & numerous in ruminants, accompanied by vacuoles in dogs, and rod-shaped in cats. Basophils have purple-black granules, are numerous in large animals and may be almost absent in healthy dogs and cats.

Normal WBCs in different species, some examples (1) (2) Eosinophil Eosinophil and neutrophil (3) Basophil (4) Eosinophil and neutrophils

REPORTING A DIFFERENTIAL COUNT By relative % of each WBC type (INCORRECT) Ways to report the values By absolute number of each WBC type (CORRECT) (%of each cell type x total WBC number)

EXAMPLE • Dog nº1 : 70% segmented and 10.0 x 109/L WBCs % Segmented neutrophils Absolute segmented neutrophils x 109/L • Dog nº1 : 70 (NORMAL) 7.0 NORMAL • Dog nº2: 70 (NORMAL) 0.7 (DECREASED) • Dog nº3 : 70 (NORMAL) 35.0 (INCREASED)

INTERPRETING DIFFERENTIAL RESULTS Neutrophilia Eosinophilia Basophilia Lymphocytosis Monocytosis  in a particular leukocyte Suffix “penia” (i.e. Lymphopenia)  in a particular leukocyte