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March 2022 Quick Question: Measuring Anti-Xa DOACs

Please review and answer our March 2022 Quick Question, submitted by colleague and coagulation expert Dave McGlasson. Although the US FDA has never approved the chromogenic anti-Xa assay for the direct oral anticoagulants rivaroxaban and apixaban, calibrators and controls are available from several distributors. Many facilities are called upon to assay for plasma concentration in certain, often emergent cases, on a research use only [RUO] basis. We’d like to learn how many of us are using the chromogenic anti-Xa with specific calibrators as opposed to those relying on the unfractionated or hybrid heparin curve, or whether we employ the clot-based methods. As always, you are invited to add a comment. Dave would also like to learn how many are using the hybrid curve for routine heparin monitoring using the chromogenic anti-Xa.

McGlasson DL. Monitoring unfractionated heparin and low molecular weight heparin anticoagulation with an anti-Xa chromogenic assay using a single calibration curve.  Lab Medicine. 2005;36:297–9.

McGlasson DL et al:  Effects of pre-analytical variables on the anti-Xa chromogenic assay when monitoring unfractionated heparin and low molecular weight heparin anticoagulation.  Blood Coagulation and Fibrinolysis. 2005;16:173–6. 

Comments (1)
Anticoagulant Therapy
Mar 7, 2022 3:05pm

Hi George and Dave:

Hi George and Dave:

Currently, the anti-Xa assay for Apixaban is FDA approved from Werfen/IL and can be run on the ACL TOP analyzers. So labs having these analyzers may be running them. Some Labs which do not prefer to run RUO assays, may run the anti-Xa LMWH assay to get a qualitative answer of whether the drug (Apixaban or Rivaroxaban) is present, based on my experience. Sometimes based on physician requests, a PT test is also run to give a very subjective conclusion of the presence of the drug.
More and more labs are preferring to use the hybrid curve for routine heparin monitoring because of the easy of use – less time needed for calibration in comparison to separate calibrations for LMWH and UFH assays, and hence less time to perform lot roll overs, etc.

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