Description:
<jats:sec><jats:title>Introduction:</jats:title><jats:p> Estimation of residual rivaroxaban plasma concentrations may be requested before invasive procedures and some patients at high thromboembolic risk will have a bridging therapy with heparins when rivaroxaban is interrupted. </jats:p></jats:sec><jats:sec><jats:title>Objective:</jats:title><jats:p> The objective of this study was to assess 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, in patients with and without bridging with low-molecular-weight heparins (LMWHs). </jats:p></jats:sec><jats:sec><jats:title>Materials and Methods:</jats:title><jats:p> Seventy-nine blood samples were collected from 77 patients on rivaroxaban at C<jats:sub>TROUGH</jats:sub> or before an invasive procedure. Rivaroxaban plasma concentrations were estimated using Biophen DiXaI, Biophen DiXaI LOW, and STA LAX and compared to liquid chromatography coupled with mass spectrometry (LC-MS/MS) measurements. Stratifications were performed according to heparin bridging. </jats:p></jats:sec><jats:sec><jats:title>Results:</jats:title><jats:p> The Biophen DiXaI LOW and STA LAX showed better correlation with LC-MS/MS measurements than Biophen DiXaI in patients not bridged with LMWH (R: 0.97, 0.96, and 0.91, respectively). However, the performance of Biophen DiXaI LOW and STA LAX decreased when residual LMWH activity was present (R: 0.18 and 0.19 respectively) demonstrating that these tests are not specific to rivaroxaban. </jats:p></jats:sec><jats:sec><jats:title>Conclusion:</jats:title><jats:p> In patients not bridged with LMWH, we suggest to use the Biophen DiXaI LOW and STA LAX for the estimation of rivaroxaban concentrations <50 ng/mL. These results should be confirmed on a larger cohort of patients. Patients bridged with LMWH have inaccurate estimates of low levels of rivaroxaban and the 3 assays studied should not be used to estimate if it is safe to perform a procedure. </jats:p></jats:sec>