Page 329 - The Veterinary Laboratory and Field Manual 3rd Edition

298 Susan C. Cork and Roy Halliwell

Table 5.5 Simplified explanation of various changes to white cell populations
in blood samples. For more information consult the bibliography at the end of
the chapter.

Test Cell type result and interpretation
Total white All white cells High (leukocytosis) – Inflammatory response, may indicate infection
cell count* or severe tissue damage anywhere in the body. It may also indicate
abnormal white cell production. Further interpretation requires a
differential white cell count. Mild elevation may be seen as part of the
normal ‘stress’ response.
Low (leukopaenia) – May indicate immunosuppresion due to a disease
process (especially viral disease) or abnormal white cell production as
seen in leukaemia and many neoplastic diseases. Further interpretation
requires a differential white cell count and assessment of cell
morphology.
Differential Neutrophils High (neutrophilia) – Usually indicates the presence of an infection
white cell (including bacterial). Immature neutrophils are present in the blood when
count demand is greater than supply, this is known as a ‘left shift’. This can
indicate a guarded prognosis if the number of mature neutrophils starts
to fall significantly.
Low (neutropaenia) – May occur if circulating neutrophils are
concentrated in tissues at the site of inflammatory response.
A lower magnitude increase in neutrophils can also be a result of
physiologic stress (cortisol induced).
Eosinophils High (eosinophilia) – May indicate an allergic reaction or parasitism. Small
rises occur in stress but numbers tend to be low in healthy animals.
Basophils Numbers are low in normal animals.
Lymphocytes High (lymphocytosis) – May indicate an active immune response to a
viral or other infectious agent or a neoplastic change.
Low (lymphopaenia) – May be associated with overwhelming viral attack,
stress or shock. If persistent, it can indicate a very guarded prognosis.
Monocytes High (monocytosis) – Levels are elevated in chronic disease as numbers
increase to remove built up tissue debris. A mild monocytosis can occur
with physiological stress.
Platelet count Platelets Low (thrombocytopaenia) – Often associated with chronic disease and
may indicate bone marrow damage due to neoplastic, viral or auto-
immune disease. It can also occur transiently after acute haemorrhage
and is a feature of DIC. Thrombocytopaenia is often associated with
blood clotting defects but further tests will be required to determine the
cause of the problem.
Notes: *The total white cell count may be high, low or normal during a disease process and the differential white cell count may
alter during the course of the disease. DIC = disseminated intravascular coagulation.

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