Background: Apixaban use has been increasing as an alternative to VKA and even other direct oral anticoagulants. Although monitoring is not required, detection of drug effect is important in determining need for anticoagulant reversal in bleeding patients. Andexanet Alfa (Portola Pharmaceuticals, San Francisco, CA), a reversal agent for Apixaban and Rivaroxaban, carries a boxed warning for thromboembolic and ischemic risks due to inhibition of tissue factor pathway inhibitor and Annexa full study report excluded patients from hemostatic efficacy with Apixaban levels < 75 ng/mL. Anti-Xa assays with Apixaban calibrators are not routinely available and, thus, there is a clinical need for a routine test to detect Apixaban effect/level because PT is insensitive.

Aims: To determine if a ready to use liquid heparin anti-Xa assay can be used as a surrogate for Apixaban anti-Xa.

Methods: Forty discarded samples from 30 patients on Apixaban were frozen between May-October 2019. Low molecular weight heparin (LMWH) anti-Xa assay (Innovance Heparin, Siemens, Marburg, Germany) was performed on each sample. If results were >1.5IU/ml, the upper limit of detection, samples were diluted 1:5 with standard plasma and run to obtain discrete values. Apixaban anti-Xa assay (Hyphen, Neuville-Sur-Oise, France), a previously validated laboratory developed test, was concurrently run on these 40 samples. To obtain additional lower end values, 20 samples were selected in which Apixaban levels were between 100-200 ng/mL. These samples were diluted 1:1; both Apixaban and LMWH assays were then run. All assays were run on the BCP XP (Siemens). Linear regression analysis was used to assess degree of correlation between LMWH anti-Xa activity and Apixaban levels.

Results: LMWH anti-Xa shows good correlation with Apixaban assay (R²=.86) (see Figure 1).

Conclusions: LMWH anti-Xa assay can be used as a surrogate to detect clinically relevant amounts of Apixaban.

[Figure 1]

« Back to ISTH 2020 Congress

ISTH Congress Abstracts - https://abstracts.isth.org/abstract/use-of-liquid-low-molecular-weight-heparin-anti-xa-assay-for-detection-of-apixaban/