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Author Notes:

CLM, WHA, AD, AR, and AI were involved in data acquisition and analysis. CLM wrote the initial manuscript, which was commented on and edited by all authors. CLM, AD, and JR oversaw the experimental design.

Cheryl L. Maier, Department of Pathology and Laboratory Medicine, 615 Michael Street, Suite 105, Atlanta, GA 30322. Email: cheryl.maier@emory.edu



  • Science & Technology
  • Life Sciences & Biomedicine
  • Hematology

Using an old test for new tricks: Measuring direct oral anti-Xa drug levels by conventional heparin-calibrated anti-Xa assay


Journal Title:



Volume 94, Number 5


, Pages E132-E134

Type of Work:

Article | Post-print: After Peer Review


The much-anticipated arrival of andexanet alfa, a recombinant factor Xa decoy protein that rapidly reverses the anticoagulant effects of direct oral factor Xa inhibitors (FXai) like apixaban and rivaroxaban,1 has many hospital systems wondering how to manage patients who may benefit from reversal but fall outside clear indications. For example, patients with delayed drug clearance due to renal failure may experience major bleeding or require emergent surgery. A recent perspective article in Blood provides an excellent overview of FXai testing and highlights both the limited availability and clinical need for drug-specific FXai testing in critical situations.2 While development of rapid drug-specific assays is underway, methods to quantitate FXai concentrations quickly, especially given the high cost of antidote, are needed right now. Herein, we provide data suggesting that conventional heparin-calibrated anti-Xa tests, performed using standard coagulometers in many U.S. hospitals, may help guide appropriate and cost-effective use of FXai antidote.
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