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Platelet Studies
Platelets are cell fragments in blood that are essential
for hemostasis, the process of controlling bleeding. If a dog or cat does not
have a sufficient number of platelets (thrombocytopenia) or the platelets do
not function properly (thrombopathia), the animal may experience spontaneous
bleeding or uncontrolled hemorrhage following surgery or trauma. Dogs and cats
with hereditary thrombopathias may experience bleeding from an early age but
it also may not be noted until later in life. The bleeding is most often manifested
as hemorrhage into the skin (petechiae and ecchymoses) or from the nose, gingiva,
gastrointestinal tract, or urinary tract.
We have studied hereditary thrombopathias in dogs and cats during
the past decade. A thrombopathia is suspected in animals presenting with a history
of surface bleeding, normal platelet count, normal coagulation screen, and normal
plasma von Willebrand factor concentration. A screening test for platelet function
defects that can be easily performed in general veterinary practice is the buccal
mucosal bleeding time test (BMBT), a procedure in which a template (e.g., Simplate
II, Organon Tecknika Corp) is used to make standardized incisions on the everted
mucosa of the upper lip. If the BMBT is prolonged (>4 minutes in the dogs,
>2 minutes in the cat), specific platelet function tests should be considered.
However, a normal BMBT does not preclude the diagnosis of a thrombopathia; therefore,
platelet function testing should still be considered if the history and clinical
signs are suggestive of a thrombopathia.
Several inherited thrombopathias have been described in a few
breeds and new thrombopathias are being identified in other breeds of dogs and
cats.
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Platelet Defect
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Breed
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Thrombasthenia (GPIIb/IIIa deficiency)
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Otterhound, Great Pyrenees
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Signal transduction defect
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Basset hound, Spitz
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delta-storage pool disease (delta-SPD)
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American Cocker spaniel
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Chediak-Higashi syndrome
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Persian cat
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Special platelet function testing performed in our laboratory
includes platelet aggregation studies (optical and impedance methods) and measurement
of platelet granule contents (ADP and ATP). Platelet function studies require
use of fresh (<3 hours old), citrate-anticoagulated whole blood. Therefore,
blood samples for platelet testing cannot be sent through the mail; rather,
the dog or cat must be presented to the Veterinary Hospital of the University
of Pennsylvania on a prearranged date to perform these studies.
Only on prearranged date. Please contact Dr. Beth Callan (215)
898-3999
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