Related Experiment Video
Updated: Oct 19, 2025

Rapid Point-of-Care Assay of Enoxaparin Anticoagulant Efficacy in Whole Blood
Published on: October 12, 2012
From Activated Partial Thromboplastin Time to Antifactor Xa and Back Again
Jori E May1, Rance Chad Siniard2, Laura J Taylor3
1Division of Hematology and Oncology, Department of Medicine, University of Alabama at Birmingham, Birmingham, USA.
Objectives:
Monitoring is essential to safe anticoagulation prescribing and requires close collaboration among pathologists, clinicians, and pharmacists.
Methods:
We describe our experience in the evolving strategy for laboratory testing of unfractionated heparin (UFH).
Results:
An intrainstitutional investigation revealed significant discordance between activated partial thromboplastin time (aPTT) and antifactor Xa (anti-Xa) assays, prompting a transition from the former to the latter in 2013. With the increasing use of oral factor Xa inhibitors (eg, apixaban, rivaroxaban, edoxaban, betrixaban), which interfere with the anti-Xa assay, we adapted our protocol again to incorporate aPTT in patients admitted on oral Xa inhibitors who require transition to UFH.
Conclusions:
Our experience demonstrates key challenges in anticoagulation and highlights the importance of clinical pathologists in helping health systems adapt to the changing anticoagulation landscape.
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