A universal anti-Xa assay for rivaroxaban, apixaban, and edoxaban measurements: method validation, diagnostic accuracy and external validation.

A universal anti-Xa assay for the determination of rivaroxaban, apixaban and edoxaban drug concentrations would simplify laboratory procedures and facilitate widespread implementation. Following two pilot studies analysing spiked samples and material from 698 patients, we conducted a prospective multicentre cross-sectional study, including 867 patients treated with rivaroxaban, apixaban or edoxaban in clinical practice to comprehensively evaluate a simple, readily available anti-Xa assay that would accurately measure drug concentrations and correctly predict relevant levels in clinical practice. Anti-Xa activity was measured by an assay calibrated with low-molecular-weight heparin (LMWH) in addition to ultra-high performance liquid chromatography-tandem mass spectrometry (LC-MS/MS). As an external validation, LMWH-calibrated anti-Xa activity was also determined in nine external laboratories. The LMWH-calibrated anti-Xa activity correlated strongly with rivaroxaban, apixaban or edoxaban drug levels [r <sub>s</sub> = 0·98, 95% confidence interval (CI) 0·98-0·98]. The sensitivity for the clinically relevant cut-off levels of 30, 50 and 100 µg/l was 96·2% (95% CI 94·4-97·4), 96·4% (95% CI 94·4-97·7) and 96·7% (95% CI 94·3-98·1) respectively. Concordant results were obtained in the external validation study. In conclusion, a universal, LMWH-calibrated anti-Xa assay accurately measured rivaroxaban, apixaban and edoxaban concentrations and correctly predicted relevant drug concentrations in clinical practice

Impact of rivaroxaban on point-of-care assays.

Point-of-care testing (POCT) is regularly used to assess haemostasis in various clinical settings. The impact of rivaroxaban on those POCT is still elusive. We aimed to study the effects of rivaroxaban on most commonly used POCT assays. Blood samples were taken before, 3h, and 24h after administration of 20mg rivaroxaban to 20 healthy volunteers as part of a prospective, multicenter validation study (clinicaltrials.govNCT01710267). Blood samples were analysed with thromboelastometry (ROTEM®), two platelet function assays (INNOVANCE® PFA-200 and Multiplate®), and the CoaguChek® XS. Rivaroxaban plasma levels were determined using liquid chromatography-mass spectrometry. Rivaroxaban significantly modified some thromboelastometry parameters (CT INTEM: mean difference 56.1s, 95% CI: 41.8, 70.3; CT EXTEM: 47.5s, 95% CI: 37.8, 57.1; CT HEPTEM: 50.1s, 95% CI: 34.7, 65.6), and CoaguChek® XS parameters (prothrombin time: mean difference 3.8s, 95% CI: 3.3, 4.2; INR: 0.32, 95% CI: 0.27, 0.38; prothrombin ratio: -36.1%, 95% CI: -32.3, -39.9). CT EXTEM and INR showed a moderate correlation with rivaroxaban plasma levels (r=0.83; 95% CI 0.69, 0.9 and r=0.83; 95% CI 0.70, 0.91, respectively) and a high sensitivity to detect rivaroxaban treatment at peak levels (0.95; 95% CI: 0.76, 1.0 and 0.90, 95% CI 0.70, 0.99, respectively). Rivaroxaban 20mg treatment significantly alters ROTEM® and CoaguChek® XS parameters. Even though POCT do not allow precise quantification of rivaroxaban plasma concentration, CT EXTEM and CoaguChek XS detect the presence of rivaroxaban at peak level with a high sensitivity

Accuracy of a Single, Heparin-Calibrated Anti-Xa Assay for the Measurement of Rivaroxaban, Apixaban, and Edoxaban Drug Concentrations: A Prospective Cross-Sectional Study.

Applying a single anti-Xa assay, calibrated to unfractionated heparin to measure rivaroxaban, apixaban, and edoxaban would simplify laboratory procedures and save healthcare costs. We hypothesized that a heparin-calibrated anti-Xa assay would accurately measure rivaroxaban, apixaban, and edoxaban drug concentrations and correctly predict clinically relevant drug levels. This analysis is part of the Simple-Xa study, a prospective multicenter cross-sectional study conducted in clinical practice. Patients treated with rivaroxaban, apixaban, or edoxaban were included. Anti-Xa activity was measured using the Siemens INNOVANCE <sup>®</sup> Heparin assay. Drug concentrations were determined using ultra-high performance liquid chromatography-tandem mass spectrometry (LC-MS/MS). Cut-off levels were determined in a derivation dataset (50% of patients) and sensitivities and specificities were calculated in a verification dataset (50% of patients). Overall, 845 patients were available for analysis. Correlation coefficients (r <sub>s</sub> ) between the heparin-calibrated anti-Xa assay and drug concentrations were 0.97 (95% CI 0.97, 0.98) for rivaroxaban, 0.96 (0.96, 0.97) for apixaban, and 0.96 (0.94, 0.99) for edoxaban. The area under the receiver operating characteristics curve (ROC) was 0.99 for all clinically relevant drug concentrations. In the verification dataset, the sensitivity was 94.2% (95% CI 90.8-96.6) for 30 μg L <sup>-1</sup> , 95.8% (92.4-98.0) for 50 μg L <sup>-1</sup> , and 98.7% (95.5-99.9) for 100 μg L <sup>-1</sup> . Specificities were 86.3% (79.2-91.7), 89.8% (84.5-93.7), and 88.7% (84.2-92.2), respectively. In a large prospective study in clinical practice, a strong correlation of heparin-calibrated anti-Xa measurements with LC-MS/MS results was observed and clinically relevant drug concentrations were predicted correctly

Management of bleeding events and invasive procedures in patients with haemophilia A without inhibitors treated with emicizumab.

Emicizumab (Hemlibra®, Hoffmann-La Roche, Switzerland) is now available for haemophilia A patients with or without factor VIII inhibitors. Management of bleeding events and replacement therapy for invasive procedures have to be adapted. To provide a practical guidance for the management of breakthrough bleeding events and elective or urgent surgery in adult and paediatric patients with haemophilia A without inhibitors treated with emicizumab. Based on the available literature and the experiences collected from adult and paediatric patients treated in Switzerland, the Working Party on Haemostasis of the Swiss Society of Haematology and the Swiss Haemophilia Network worked together to reach a consensus on the management of bleeding events and invasive procedures. Minor bleeding events and invasive procedures associated with low bleeding risk can be treated without factor replacement therapy in most cases, whereas major bleeding events and high-risk surgery require additional factor VIII replacement at usual doses, at least for the first days. Emicizumab treatment should be continued throughout the procedure and during the postoperative period. Elective major surgery should be planned according to emicizumab dosing for patients with a once-a-month posology. Of note, so far only few data are available on the management of major bleeds and surgery in patients with haemophilia A treated with emicizumab and this practical guidance will have to be regularly updated with growing experience. &nbsp