Veterinary Medicine - August 2007 - (Page 533)

Treatment should not be withheld pending the results of antiplatelet antibody testing. Demonstration of antiplatelet antibodies (Table 3) may support a diagnosis of immune-mediated thrombocytopenia but is not always necessary.8 Indirect assays (e.g. the platelet factor 3 test) detect platelet-bindable antibody in serum or plasma and have low sensitivity and specificity; these assays are no longer available.13 Direct assays (e.g. flow cytometric assays, radioimmunoassays, or ELISAs) detect plateletsurface-associated antibodies and have higher sensitivity.2,5 Assays that measure total antibody are not reliable; assays that detect platelet surfaceassociated immunoglobulin should be used.4 Alternatively, the antimegakaryocyte antibody test may be performed from slides of bone marrow aspirates.13 Treatment should not be withheld pending antiplatelet antibody test results. An additional limitation of antiplatelet antibody testing is that it does not differentiate primary from secondary immune-mediated thrombocytopenia.2,5,8 Secondary causes of immune-mediated thrombocytopenia must be ruled out by appropriate diagnostic testing because response to immunosuppressive therapy is the final step in confirming immune-mediated thrombocytopenia, but some patients with secondary etiologies may respond positively initially.2,6 Death is mainly from acute GI hemorrhage or euthanasia.8 Aggressive initial therapy may improve survival rates. About 25% of dogs with immunemediated thrombocytopenia require long-term medication, and side effects are a principal reason for euthanasia in these patients.8 Recurrence after a variable period of clinical remission is common, occurring in about 40% of dogs.2,8 Initial supportive therapy The initial management goals with immune-mediated thrombocytopenia are to stop bleeding, halt platelet destruction, and treat any concurrent disease. 6 A variety of supportive measures are indicated for a patient with severe thrombocytopenia. Ideally the patient should be hospitalized and allowed to rest in a padded cage, with gentle handling to minimize trauma-related hemorrhage.2,18 Soft diets are fed to minimize gingival trauma.18,19 Avoid cystocentesis and intramuscular injections. 18,19 Also avoid jugular venipuncture in patients with severe thrombocytopenia, and apply direct pressure to any venipuncture or injection site for five minutes to ensure hemostasis. Intravenous catheters are not contraindicated, but if a jugular catheter is required, placement should be done with great care, optimally after a transfusion with platelet-rich plasma.18 If the patient is hypovolemic, give crystalloids, colloids, or blood products as necessary.2 Hemodilution with synthetic colloids may decrease platelet function, so they should be used judiVETERINARY MEDICINE August 2007 TREATMENT Immune-mediated thrombocytopenia is a serious and potentially lifethreatening disorder.8 Mortality rates of the initial episode of thrombocytopenia or relapse range from 25% to 30%.2,8 533 http://virbacvet.com http://virbacvet.com

Table of Contents Feed for the Digital Edition of Veterinary Medicine - August 2007

Contents A Veterinary Medicine Interview Veterinary Voices Idea Exchange Diagnosis and Treatment of Solar Dermatitis in Dogs Diagnostic Imaging for Linear Foreign Bodies in Cats Overcoming the Diagnostic and Therapeutic Challenges of Canine Immune-Mediated Thrombocytopenia Ophthalmic drugs: What’s new? CE Form Product Preview Advertiser Index Marketplace/Classifieds Mind Over Miller

Veterinary Medicine - August 2007

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