IM01 - Plasma ADAMTS13 activity in dogs with severe thrombocytopenia and presumed immune thrombocytopenia

Abstract: Background - In humans, deficiency of ADAMTS13, a von Willebrand factor cleaving enzyme, is an important cause of thrombocytopenia and difficult to differentiate from immune thrombocytopenia (ITP). Hypothesis/Objectives - Dogs with presumed ITP have reduced ADAMTS13 activity compared to healthy dogs and bleeding assessment scores (DOGiBAT) negatively correlate with ADAMTS13 activity. Animals - Fifteen privately-owned dogs with presumed ITP and 40 healthy dogs enrolled in a separate study recruited from a hospital population. Methods - Prospective observational study. Dogs (≥ 1 year of age) with severe thrombocytopenia (≤20,000 platelets/uL) underwent diagnostic evaluation and were categorized as having presumed primary ITP (pITP) or ITP with concurrent disease. All dogs received a DOGiBAT score. Plasma ADAMTS13 activity was assessed using the Diapharma® RUO Technozyme® ADAMTS13 Activity ELISA kit. Wilcoxon rank sum test was used to determine if ADAMTS13 was significantly different in dogs with ITP compared to healthy controls. Spearman’s rank correlation rho test was used to determine if ADAMTS13 activity correlates with bleeding scores. Results - Preliminary results: Dogs with presumed ITP have reduced plasma ADAMTS13 activity compared to healthy controls (P = 0.039). Individually, plasma ADAMTS13 activity in dogs with pITP or ITP with concurrent disease is not different from healthy controls (P = 0.428, P = 0.095, respectively). ADAMTS13 activity does not correlate with DOGiBAT scores (P = 0.069). Conclusions and Clinical Importance - ADAMTS13 deficiency may be a mechanism for thrombocytopenia in some dogs with severe thrombocytopenia that are labeled as having ITP.