Overview

The study of number and morphology of cellular elements of the blood- the RBCs, WBCs, and the platelets can be used to diagnose and monitor diseases.

Companion animals suffer from diseases of all blood cells and deficiencies of proteins contained in the plasma which are responsible for normal blood coagulation.

Common Hematologic Diseases of Dogs And Cats

  • Hemophilia- a deficiency of blood clotting proteins
  • Von Willebrand’s disease- most common canine inherited blood disorder
  • Thrombocytopenia- deficiency of platelets
  • Anticoagulant rodenticide intoxication- deficiency of blood clotting proteins
  • Hemolytic anemia- excessive destruction of RBCs
  • Immune mediated neutropenia- excessive destruction of WBCs
  • Myelodysplasia- abnormal bone marrow function

Study of RBCs

Some RBC measurements are routinely done:

  1. Packed cell volume (PCV): It is usually used to assess the basic status of the erthron (increased in polycythemia and decreased in anemia).
  2. The proportion of whole blood volume occupied by the RBCs
  3. Hemoglobin (Hb) concentration of whole lysed blood

RBC count (the number of RBCs per unit volume of whole blood)

Study of WBCs

WBCs consist of the granulocytes (neutrophils, eosinophils and basophils) and agranulocytes (lymphocytes and monocytes).

Meaningful interpretation can only be made if the absolute number of each of these type is calculated. Percentages of each cell type alone are not helpful at all.

Study of Platelets

Mammalian platelets are pale blue granular fragments smaller than RBCs. they maintain the clotting process and ensure mechanical strength of the clot.

Increased platelet count occurs-

  • as a reaction to consumption after injury,
  • after splenectomy (removal of spleen),
  • after vincristine treatment as chemotherapy medication
  • and megakaryocytic leukemia.

Decreased platelet counts are caused by-

  • Autoimmune reactions
  • Thrombotic purpura
  • Bone marrow suppression and aplasia
  • Bone marrow neoplasia
  • And equine infectious anemia

Hematology Testing

Commonly performed group tests include:

  • Routine hemogram (CBC): This is performed in all mammalian species with a hematology analyser. It provides:
  • WBC results (WBC count, differential cell count and leukocyte morphology),
  • red cell results (RBC count, hemoglobin concentration, hematocrit, RBC indices and RBC morphology),
  • platelet results (platelet count, mean platelet volume and smear estimate),
  • total protein (by refractometer) and
  • plasma appearance.

Reticulocyte count is automatically added to a CBC in anemic dogs and cats which gives a more accurate assessment of the bone marrow response to anemia.

  • Non mammalian CBC: It is done in animals in which only small amount of blood can be collected.
  • Automated hemograms: It is also called an automated WBC panel. It is, however, only available for certain species. It is recommended for research samples and for pre-surgical screening in relatively healthy animals.

Individual tests: Sometimes only specific component of the blood needs to be tested for, this is where individual tests come in. This is useful for research samples.

These include:

  • reticulocyte count,
  • fibrinogen by heat precipitation (it is an acute phase reactant protein elevated values of which indicate inflammation and renal disease), and

Fecal occult blood test (it helps in confirming suspected gastrointestinal blood loss and is performed on feces).