EDTA-DEPENDENT PSEUDOTHROMBOCYTOPENIA IN A HORSE

Hematologic evaluation of a 7-year-old Thoroughbred mare prior to celi otomy for large colon displacement and sand impaction revealed thrombo cytopenia (17,000 platelets/mu l). An enterotomy was performed to remo ve the impaction. Heparin, which was commenced intraoperatively, was c ontinued postsurgery because of persistent thrombocytopenia attributed to ongoing disseminated intravascular coagulation. Heparin was discon tinued after 48 hours due to suspected heparin-induced anemia. Despite uneventful recovery, thrombocytopenia persisted. EDTA-dependent pseud othrombocytopenia is a rare phenomenon that should be considered in ho rses with thrombocytopenia, absence of clinical bleeding, and no appar ent etiology for thrombocytopenia. Abnormal platelet counts should alw ays be verified by examination of a peripheral blood smear. EDTA-depen dent pseudothrombocytopenia is best investigated by repeating platelet counts on blood freshly anticoagulated with Na(3)citrate.