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Thromb Haemost. 2014 Feb;111(2):240-8. doi: 10.1160/TH13-06-0470. Epub 2013 Oct 31.

Assessment of apixaban plasma levels by laboratory tests: suitability of three anti-Xa assays. A multicentre French GEHT study.

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Isabelle Gouin Thibault, Laboratoire d'Hématologie, Groupe Hospitalier Cochin-Hôtel Dieu, 27, rue du Faubourg Saint-Jacques, 75 679 Paris Cedex 14, France, Tel.: +33 1 42 34 84 47, Fax: +33 1 58 41 19 97, E-mail:


While laboratory monitoring is not required in patients treated with apixaban, a direct factor-Xa inhibitor, assessment of its concentration is useful in some critical situations. However, few data are available on its effect on coagulation tests and on the suitability of anti-Xa assays for its quantification. It was the objective of this study to identify laboratory tests suitable for apixaban concentration assessment. Coagulation tests - PT and aPTT- and anti-Xa assays were performed in apixaban-spiked plasma samples. To evaluate the sensitivity of PT and aPTT to apixaban, we conducted a first monocenter part, with a wide range of concentrations (50-1,000 ng/ml), a large panel of reagents (20 reagents), and two coagulometers (STAR®, Stago and ACL TOP®, IL), and a second multicenter part involving 13 laboratories using either a common PT reagent (RecombiPlastin2G®) or the local PT and aPTT reagents. In the multicentre part, five blinded apixaban-spiked plasma samples (0/100/200/400/800 ng/ml - checked by HPLC-MS/MS) were used; apixaban concentrations were measured with three anti-Xa assays, apixaban calibrators and controls (Stago). PT and aPTT tests using a large panel of reagents displayed a low sensitivity to a wide range of apixaban concentrations. The concentrations to double PT ranged from 400 to >1,000 ng/ml with the 10 reagents. With the three anti-Xa assays, inter-laboratory precision and accuracy were below 11% and 12%, respectively. In conclusion, whereas PT and aPTT tests were not sensitive enough to detect apixaban, the three anti-Xa assays tested using lyophilised apixaban calibrators and controls allowed to reliably quantify a wide range of apixaban concentrations.


Apixaban; anti-Xa; anticoagulant agents; blood coagulation tests; multicenter study

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