Assessment of low plasma concentrations of apixaban in the periprocedural setting.

Estimation of residual apixaban plasma concentrations may be requested in the management of emergencies. This study aims at assessing the performance of specific anti-Xa assays calibrated with apixaban on real-life samples with low apixaban plasma concentrations (<30 ng/mL) and on-treatment ranges, with and without interference of low-molecular-weight heparin (LMWH). The performance of the STA® -Liquid Anti-Xa assay (STA® LAX) and the low and normal procedures of the Biophen® Direct Factor Xa Inhibitors (DiXaI) assay was tested on 134 blood samples, collected from patients on apixaban, wherefrom 74 patients received LMWH after apixaban cessation. The results were compared with the liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) measurements. The Biophen® DiXaI, Biophen® DiXaI LOW, and STA® LAX showed very good correlation with LC-MS/MS measurements in patients without LMWH administration (Spearman r .95, .99, and .98, respectively). Their limits of quantitation were defined at 48, 24, and 12 ng/mL, respectively. The Bland-Altman test measured mean bias (SD) at 5.6 (13.1), -2.5 (5.0), and -0.8 (6.1) ng/ml, respectively. The Spearman r of the Biophen® DiXaI decreased to 0.64 in presence of low apixaban concentrations. The Spearman r of the Biophen® DiXaI LOW and STA® LAX decreased to 0.39 and 0.26, respectively, in presence of LMWH. The accuracy of the low methodologies (Biophen® DiXaI LOW and STA® LAX) is slightly improved for low apixaban plasma concentrations, compared with the normal procedure of Biophen® DiXaI. The interference of LMWH on the low methodologies is measurable, however, less important than the previously reported interference of LMWH on rivaroxaban calibrated specific anti-Xa assays.

Lessire S ，Dincq AS ，Siriez R ，Pochet L ，Sennesael AL ，Vornicu O ，Hardy M ，Deceuninck O ，Douxfils J ，Mullier F ... -  《-》

Estimation of Rivaroxaban Plasma Concentrations in the Perioperative Setting in Patients With or Without Heparin Bridging.

Lessire S ，Douxfils J ，Pochet L ，Dincq AS ，Larock AS ，Gourdin M ，Dogné JM ，Chatelain B ，Mullier F ... -  《-》

Using a low-molecular weight heparin-calibrated anti-factor Xa assay to assess the concentration of apixaban and rivaroxaban.

Direct oral anticoagulant (DOAC)-inhibiting factor Xa (FXa-DOAC) are being increasingly used as prophylaxis of venous thromboembolism and for prevention of stroke in patients with atrial fibrillation. In contrast to vitamin K antagonists, DOACs do not require monitoring in general. However, it is sometimes of value in the acute setting, for instance when considering a reversal agent in uncontrolled bleeding in patients on DOAC. We evaluated if a low-molecular weight heparin (LMWH)-calibrated anti-factor Xa assay could be used to estimate FXa-DOAC concentration in the concentration range <100 ng/mL by spiking known concentrations of FXa-DOAC and from those result calculate the FXa-DOAC concentration from the response of the LMWH assay. This procedure was then evaluated by comparing the result with a drug-calibrated chromogenic assay and liquid chromatography tandem mass spectrometry (LC-MS/MS) on clinical plasma samples from patients treated with apixaban or rivaroxaban. Although the measuring range was narrower for the LMWH-calibrated assay, concentrations recalculated from the LMWH assay was comparable with those measured by the drug-calibrated method when compared with LC-MS/MS. We suggest that an LMWH-calibrated anti-factor Xa assay can be used after characterization of the response of FXa-DOACs to give guidance on the concentration of apixaban and rivaroxaban. Shorter turnaround time than LC-MS/MS and the greater availability than drug-calibrated chromogenic assays could make this a valuable option in the acute setting.

von Horn H ，Rasmusson A ，Söderblom L ，Malmström RE ，Antovic J ... -  《-》

Preliminary report: Measurement of apixaban and rivaroxaban in plasma from bleeding patients.

The direct oral anticoagulants (DOACs), apixaban and rivaroxaban, are used for anticoagulation treatment. Although biochemical monitoring is not required, severe bleedings caused by DOAC have been reported. We therefore evaluated the chromogenic assay Biophen DiXaI® (Biophen) using plasma from non-bleeding patients in treatment with DOAC and on spiked plasma from patients with ongoing bleeding. The Biophen method was compared with an in-house reference method; liquid chromatography-tandem mass spectrometry (LC-MS/MS) using plasma spiked with the compounds ranging from 20 to 1500 μg/L. Furthermore, the methods were compared using plasma from non-bleeding patients in treatment with DOAC (n = 106). In addition, plasma was collected from patients not treated with DOAC, but with ongoing bleeding and tested in spiking experiments (n = 14). Analysis of plasma from 106 patients receiving rivaroxaban (n = 91) or apixaban (n = 15) showed agreement and correlation between the methods. Measurement in spiked plasma from patients with active bleeding, however, revealed a 26% overestimation by the assay. Our findings show that Biophen is suitable for measuring apixaban and rivaroxaban concentrations in plasma. However, our results in patients with active bleeding show an overestimation of 26%. This should be taken into account when assessing possible intoxication with apixaban and rivaroxaban in patients presenting with bleeding.

Jensen KOF ，Hansen SH ，Goetze JP ，Jesting A ，Stensballe J ，Hansen H ... -  《-》

DOAC plasma levels measured by chromogenic anti-Xa assays and HPLC-UV in apixaban- and rivaroxaban-treated patients from the START-Register.

To measure direct factor Xa inhibitor (apixaban, edoxaban, rivaroxaban) concentrations, dedicated chromogenic anti-Xa assays are recommended as suitable methods to provide rapid drug quantification. Moreover, the high-performance liquid chromatography with ultraviolet detection (HPLC-UV) is reported as a reliable quantitative technique. We investigated seven anti-Xa assays and an HPLC-UV method for measurement of apixaban and rivaroxaban levels in patients enrolled in the START-Register. A total of 127 apixaban and 124 rivaroxaban samples were tested by HPLC-UV and the following anti-Xa assays: Biophen DiXaI and Heparin LRT (Hyphen BioMed), Berichrom and Innovance Heparin (Siemens), STA-Liquid Anti-Xa (Stago Diagnostics), Technochrom anti-Xa (Technoclone), and HemosIL Liquid Anti-Xa (Werfen). Each method was performed in one of the participating laboratories: Bologna, Cremona, Florence, and Padua. Our data confirmed the overestimation of apixaban and rivaroxaban levels by the antithrombin-supplemented anti-Xa method (Berichrom). Performances and reproducibility of the six anti-Xa assays not supplemented with antithrombin and the HPLC-UV method were good, with limits of quantification from 8-39 ng/mL (apixaban) and 15-33 ng/mL (rivaroxaban). The six chromogenic methods showed good concordances with the quantitative HPLC-UV [bias: -26.9-22.3 ng/mL (apixaban), -11.3-18.7 ng/mL (rivaroxaban)]. Higher bias and wider range between limits of agreement were observed at higher concentrations [<100 ng/mL: bias -21.3-4.1 ng/mL (apixaban) and -6.2-3.8 ng/mL (rivaroxaban); >200 ng/mL: bias -42.2-36.8 ng/mL (apixaban) and -20.1-68.9 ng/mL (rivaroxaban)]. Overall, the anti-Xa assays not supplemented with antithrombin and the HPLC-UV method proved to be suitable for apixaban and rivaroxaban quantification.

Cini M ，Legnani C ，Padrini R ，Cosmi B ，Dellanoce C ，De Rosa G ，Marcucci R ，Pengo V ，Poli D ，Testa S ，Palareti G ... -  《-》