In this episode, I’ll discuss checking DOAC activity before reversal agent administration.
Anti-Xa inhibitors such as apixaban, rivaroxaban, fondaparinux, and danaparoid do not have readily available assays, yet there is often a clinical need to determine their presence or absence.
Back in episode 536 I discussed how heparin anti-Xa level cutoffs could identify patients which no longer had relevant concentrations of Xa inhibitors.
This was based on a retrospective cohort study that found that with over 96% accuracy, their heparin anti-Xa cutoffs could identify patients which no longer had relevant concentrations of Xa inhibitors.
The cutoff values for screening for relevant concentrations of Xa inhibitors were as follows:
For apixaban, a heparin anti-Xa of 0.2 or less identified a patient without relevant concentrations.
For rivaroxaban, a heparin anti-Xa of 0.3 or less.
For fondaparinux and danaparoid, a heparin anti-Xa level less than 0.1.
However another strategy for determining the presence of oral factor-Xa inhibitors was recently published in AJHP.
These author’s took their laboratory’s preexisting anti-Xa reagent and calibrated it for apixaban and rivaroxaban. The result was an assay that could reliably give information as to the extent of DOAC levels present with a clinically relevant turnaround time of well under 60 minutes. Out of a group of 30 patients that presented to the ED for acute bleeding or requiring an urgent procedure that required reversal, the assay was used to rule out the presence of oral factor Xa inhibitor in 3 patients, preventing the unnecessary use of reversal agents.
This represents an alternative practice to the use of an uncalibrated heparin anti-Xa level, and could be an option if your clinical laboratory has the ability to calibrate and implement such an assay.
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