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Patients that are presented with bleeding should be evaluated for evidence of a local cause of bleeding, e.g. trauma, ulceration, and given a careful physical examination. A thorough history should be taken, including any episodes of prior hemorrhage, family history, travel history, and access to anticoagulant rodenticides. The owner should be asked carefully about the nature, site and type of hemorrhage, including frequency and any known initiating causes (e.g. excessive bleeding noted when chewing a bone). If the bleeding cannot be attributed to an obvious cause, then a series of screening tests should be done. The screening tests should include a hemogram, with particular attention to the platelet number, clinical chemistry tests (to assess for underlying diseases that can affect hemostasis), and tests that will detect deficiencies in coagulation factors or inhibitors. Estimation of platelet counts and measurement of the activated coagulation time (ACT) and buccal mucosal bleeding time (BMBT) are in-office procedures; the rest of the tests are performed in laboratories and require collection of blood samples for coagulation testing. There are many different types of instrumentation and reagents for coagulation screening tests. Most of these have been developed for use in humans and do not work in animals or the procedure needs to be adapted and optimized for animals. Dogs, in particular, have much quicker coagulation times than human beings, and instruments that cannot compensate for these rapid times (many photo-optical instruments) may miss clot formation. Furthermore, results should always be interpreted with respect to reference ranges for that species. The reference ranges for coagulation tests in human patients are much longer than dogs and cannot be used for this species. For these reasons, it is far better to send samples for coagulation testing to veterinary laboratories, as there is no doubt that all laboratories are not equal when it comes to coagulation testing. |