title: Interactions between rivaroxaban and antiphospholipid antibodies in thrombotic antiphospholipid syndrome.
abstract: BACKGROUND
  Rivaroxaban can affect lupus anticoagulant (LA) testing and antiphospholipid antibodies (aPL) may interfere with the anticoagulant action of rivaroxaban.
  
  
  OBJECTIVE
  To establish the influence of rivaroxaban on LA detection and of aPL on the anticoagulant action of rivaroxaban.
  
  
  METHODS
  Rivaroxaban and 52 IgG preparations (20 LA+ve, 12 LA-ve thrombotic antiphospholipid syndrome [APS] patients, and 20 normal controls [NC]) were spiked into pooled normal plasma (PNP) for relevant studies. LA detection was also studied in APS patients receiving rivaroxaban 20 mg once daily.
  
  
  RESULTS
  In vitro spiking of samples with rivaroxaban showed no false positive LA with Textarin time, Taipan venom time/Ecarin clotting time (TVT/ECT), dilute prothrombin time (dPT) and in-house dilute Russell's viper venom time (DRVVT), but false positives in the majority of NC and LA negative IgG with two commercial DRVVT reagents at 250 ng/mL but not 50 ng/mL rivaroxaban. Ex vivo studies: six LA+ve patients on rivaroxaban remained LA positive with TVT/ECT and DRVVT at peak (162-278 ng/mL) and trough (30-85 ng/mL) rivaroxaban levels. Six LA-ve patients became (apparently) LA+ve with two DRVVT reagents (test/confirm ratio median [confidence interval], 1.6 [1.3-1.8], 1.6 [1.4-1.9]) but not with TVT/ECT at peak rivaroxaban levels, and remained LA-ve with both DRVVT reagents and TVT/ECT at trough levels. aPL positive IgG spiking of PNP had no effect on rivaroxaban's anticoagulant action on thrombin generation or rivaroxaban anti-Xa levels.
  
  
  CONCLUSIONS
  The TVT/ECT ratio and Textarin time were not affected even at peak rivaroxaban levels, enabling detection of LA ex vivo. aPL had no effects on rivaroxaban's anticoagulant action in vitro.
authors: Haemostasis Research Unit, Department of Haematology, University College London, London, UK.
authors: D R J
authors: DR
authors: Arachchillage
authors: Haemostasis Research Unit, Department of Haematology, University College London, London, UK.
authors: I J
authors: IJ
authors: Mackie
authors: Haemostasis Research Unit, Department of Haematology, University College London, London, UK.
authors: M
authors: M
authors: Efthymiou
authors: Centre for Rheumatology, Division of Medicine, University College London, London, UK.
authors: D A
authors: DA
authors: Isenberg
authors: Haemostasis Research Unit, Department of Haematology, University College London, London, UK.
authors: S J
authors: SJ
authors: Machin
authors: Haemostasis Research Unit, Department of Haematology, University College London, London, UK.|Department of Haematology, University College London Hospitals NHS Foundation Trust, London, UK.
authors: H
authors: H
authors: Cohen
mesh_terms: D017152:Antibodies, Antiphospholipid / Q000097:blood*; D016736:Antiphospholipid Syndrome / Q000097:blood / Q000175:diagnosis / Q000188:drug therapy*; D015415:Biomarkers / Q000097:blood; D001777:Blood Coagulation / Q000187:drug effects*; D001780:Blood Coagulation Tests; D016022:Case-Control Studies; D065427:Factor Xa Inhibitors / Q000009:adverse effects / Q000627:therapeutic use*; D005189:False Positive Reactions; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D016682:Lupus Coagulation Inhibitor / Q000097:blood; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D000069552:Rivaroxaban / Q000009:adverse effects / Q000627:therapeutic use*; D013927:Thrombosis / Q000097:blood / Q000175:diagnosis / Q000188:drug therapy*; D016896:Treatment Outcome
chemical_list: D017152:Antibodies, Antiphospholipid; D015415:Biomarkers; D065427:Factor Xa Inhibitors; D007074:Immunoglobulin G; D016682:Lupus Coagulation Inhibitor; D000069552:Rivaroxaban
keywords: Russell's viper venom time; antiphospholipid syndrome; lupus anticoagulant; prothrombin activator (Taipan venom); rivaroxaban