Utility of Standard Hemostasis Tests for Diagnosing Hypercoagulability

In the Literature

Clarkin-Breslin RC, Chalifoux NV, Buriko Y. Standard tests of haemostasis do not predict elevated thromboelastographic maximum amplitude, an index of hypercoagulability, in sick dogs. J Small Anim Pract. 2024. doi:10.1111/jsap.13741

The Research …

Standard hemostasis tests (eg, prothrombin time [PT], activated partial thromboplastin time [aPTT]) are used to determine hypocoagulability, but their utility for determining hypercoagulability is unclear.¹ Viscoelastic testing (eg, thromboelastography [TEG]) reflects clot formation, strength, and lysis and has been proposed as a more useful tool for determining hypocoagulable and hypercoagulable states.^2-4

This prospective case-control study compared PT, aPTT, and D-dimers in sick dogs (n = 71) with hypercoagulable and normocoagulable states confirmed by TEG. Packed-cell volume (PCV) and platelet counts (confirmed via manual blood smear) were also measured. Of all dogs, 51% were hypercoagulable and 49% were normocoagulable based on TEG tracings. A wide range of diseases was represented. No correlation was found between standard tests of hemostasis (ie, PT, aPTT, D-dimers) and TEG; however, lower PCV and higher platelet counts were significantly associated with hypercoagulability, a finding that has been previously reported.^5,6

… The Takeaways

Key pearls to put into practice:

• PT and aPTT are not useful for diagnosing hypercoagulable states in dogs. Although several studies in human medicine and a single study in veterinary medicine show these tests may have some utility, there is not enough evidence to support their use in veterinary medicine.^7-10 PT and aPTT are useful for assessing bleeding tendencies and response to anticoagulant drug therapies (eg, factor Xa inhibitors, low molecular weight heparin), even though reference intervals have not been established.¹¹

• Viscoelastic testing can be used for prothrombotic and bleeding disorders because it provides an overall assessment of coagulation but cannot be relied on as a standalone test. Gold standards for diagnosing coagulation disorders in dogs are not available; viscoelastic test results should thus be evaluated alongside clinical presentation, disease process, and other test results (eg, PCV, platelet count) to determine whether treatment is needed.

• Prothrombotic states can occur with a wide range of disease processes. Benefits of preventing thrombosis should be weighed against risk for bleeding when selecting treatment.