What causes blood clots in dogs with immune-mediated hemolytic anemia

Abstract

BACKGROUND: Hypercoagulability is a well-known feature of canine immune-mediated hemolytic anemia (IMHA) and is believed to increase the risk of thrombosis. This study was undertaken to differentiate the relative contribution of platelets and clotting proteases to this hypercoagulability using thromboelastography (TEG). STUDY DESIGN: Retrospective observational study. METHODS: Thromboelastograms from 27 dogs with IMHA were retrospectively evaluated. Standard TEG parameters (R, K, α, MA), the G value, and the novel parameter delta (Δ) were determined. Hypercoagulability was attributed to the platelet component of hemostasis when there was an increased G value with a normal Δ value. KEY FINDINGS: Nineteen of 27 dogs (70.4%) had ≥ 2 TEG variables suggestive of hypercoagulability, 18 (66.7%) had a hypercoagulable G value, and 11 (40.7%) had a hypercoagulable Δ value. Ten of 27 (37%) samples met the criteria for platelet hypercoagulability. SIGNIFICANCE: Our report documents the derivation and application of the Δ value to differentiate enzymatic from platelet hypercoagulability. Further studies are required to validate the use of these TEG variables in this manner. The hypercoagulable tendency in dogs with IMHA is complex and multifactorial, and in some dogs this hypercoagulability may be attributed primarily to platelet hyper reactivity. Our findings may support the use of anti-platelet drugs in some dogs with IMHA.