Laboratory Testing in the Era of Direct or Non–Vitamin K Antagonist Oral Anticoagulants: A Practical Guide to Measuring Their Activity and Avoiding Diagnostic Errors

Abstract

A new generation of antithrombotic agents has recently emerged. These provide direct inhibition of either thrombin (factor IIa [FIIa]) or FXa, and are increasingly replacing the classical anticoagulants (heparin and coumarins such as warfarin) in clinical practice for a variety of conditions. These agents have been designated several acronyms, including NOACs, DOACs, and TSOACs, respectively, referring to new (novel; non–vitamin K antagonist) oral anticoagulants, direct oral anticoagulants, and target-specific oral anticoagulants, and currently include dabigatran (FIIa inhibitor), and rivaroxaban, apixaban, edoxaban, and betrixaban (FXa inhibitors). The pervading mantra that NOACs do not require laboratory monitoring is countered by ongoing recognition that laboratory testing for drug effects is needed in many situations. Moreover, since these agents “do not require” laboratory monitoring, some clinicians inappropriately take this to mean that they do not affect hemostasis tests. This review aims to briefly review the laboratory studies that have evaluated the NOACs against a wide range of laboratory assays to assess utility for qualitative or quantitative measurements of these drugs, as well as interferences that may cause misdiagnosis of hemostatic defects. Point of care testing, including use of alternate samples such as urine and serum, is also under development but is not covered extensively in this review. The main aims of this article are to provide practical guidance to general laboratory testing for NOACs, as well as to help avoid diagnostic errors associated with hemostasis testing performed on samples from treated patients, as these currently comprise major challenges to hemostasis laboratories in the era of the NOACs.

Keywords

NOACs - dabigatran - rivaroxaban - apixaban - edoxaban - measurement - interference

• References

• 1 Guyatt GH, Akl EA, Crowther M, Gutterman DD, Schuünemann HJ ; American College of Chest Physicians Antithrombotic Therapy and Prevention of Thrombosis Panel. Executive summary: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest 2012; 141 (2 Suppl) 7S-47S
• 2 Lippi G, Franchini M, Favaloro EJ. Pharmacogenetics of vitamin K antagonists: useful or hype?. Clin Chem Lab Med 2009; 47 (5) 503-515
• 3 Favaloro EJ, Lippi G, Koutts J. Laboratory testing of anticoagulants: the present and the future. Pathology 2011; 43 (7) 682-692
• 4 Lippi G, Favaloro EJ. Recent guidelines and recommendations for laboratory assessment of the direct oral anticoagulants (DOACs): is there consensus?. Clin Chem Lab Med 2015; 53 (2) 185-197
• 5 Husted S, de Caterina R, Andreotti F , et al; ESC Working Group on Thrombosis Task Force on Anticoagulants in Heart Disease. Non-vitamin K antagonist oral anticoagulants (NOACs): No longer new or novel. Thromb Haemost 2014; 111 (5) 781-782
• 6 Ruff CT, Giugliano RP, Braunwald E , et al. Comparison of the efficacy and safety of new oral anticoagulants with warfarin in patients with atrial fibrillation: a meta-analysis of randomised trials. Lancet 2014; 383 (9921) 955-962
• 7 McMahon BJ, Kwaan HC. The new or non-vitamin K antagonist oral anticoagulants: what have we learned since their debut. Semin Thromb Hemost 2015; 41 (2) 188-194
• 8 Favaloro EJ, Lippi G. The new oral anticoagulants and the future of haemostasis laboratory testing. Biochem Med (Zagreb) 2012; 22 (3) 329-341
• 9 Harenberg J, Du S, Krämer S, Weiss C, Krämer R, Wehling M. Patients' serum and urine as easily accessible samples for the measurement of non-vitamin K antagonist oral anticoagulants. Semin Thromb Hemost 2015; 41 (2) 228-236
• 10 Zolfaghari S, Harenberg J, Frölich L , et al. Development of recommendations to continue anticoagulation with one of the two types of oral anticoagulants based on the identification of patients' preference. Semin Thromb Hemost 2015; 41 (2) 166-177
• 11 van der Hulle T, Kooiman J, den Exter PL, Dekkers OM, Klok FA, Huisman MV. Effectiveness and safety of novel oral anticoagulants as compared with vitamin K antagonists in the treatment of acute symptomatic venous thromboembolism: a systematic review and meta-analysis. J Thromb Haemost 2014; 12 (3) 320-328
• 12 Loke YK, Pradhan S, Yeong JK, Kwok CS. Comparative coronary risks of apixaban, rivaroxaban and dabigatran: a meta-analysis and adjusted indirect comparison. Br J Clin Pharmacol 2014; 78 (4) 707-717
• 13 Lippi G, Favaloro EJ, Mattiuzzi C. Combined administration of antibiotics and direct oral anticoagulants: a renewed indication for laboratory monitoring?. Semin Thromb Hemost 2014; 40 (7) 756-765
• 14 Gous T, Couchman L, Patel JP, Paradzai C, Arya R, Flanagan RJ. Measurement of the direct oral anticoagulants apixaban, dabigatran, edoxaban, and rivaroxaban in human plasma using turbulent flow liquid chromatography with high-resolution mass spectrometry. Ther Drug Monit 2014; 36 (5) 597-605
• 15 Stangier J, Rathgen K, Stähle H, Gansser D, Roth W. The pharmacokinetics, pharmacodynamics and tolerability of dabigatran etexilate, a new oral direct thrombin inhibitor, in healthy male subjects. Br J Clin Pharmacol 2007; 64 (3) 292-303
• 16 Stangier J, Stähle H, Rathgen K, Fuhr R. Pharmacokinetics and pharmacodynamics of the direct oral thrombin inhibitor dabigatran in healthy elderly subjects. Clin Pharmacokinet 2008; 47 (1) 47-59
• 17 van Ryn J, Stangier J, Haertter S , et al. Dabigatran etexilate—a novel, reversible, oral direct thrombin inhibitor: interpretation of coagulation assays and reversal of anticoagulant activity. Thromb Haemost 2010; 103 (6) 1116-1127
• 18 Lindahl TL, Baghaei F, Blixter IF , et al; Expert Group on Coagulation of the External Quality Assurance in Laboratory Medicine in Sweden. Effects of the oral, direct thrombin inhibitor dabigatran on five common coagulation assays. Thromb Haemost 2011; 105 (2) 371-378
• 19 Freyburger G, Macouillard G, Labrouche S, Sztark F. Coagulation parameters in patients receiving dabigatran etexilate or rivaroxaban: two observational studies in patients undergoing total hip or total knee replacement. Thromb Res 2011; 127 (5) 457-465
• 20 Harenberg J, Giese C, Marx S, Krämer R. Determination of dabigatran in human plasma samples. Semin Thromb Hemost 2012; 38 (1) 16-22
• 21 Douxfils J, Mullier F, Robert S, Chatelain C, Chatelain B, Dogné JM. Impact of dabigatran on a large panel of routine or specific coagulation assays. Laboratory recommendations for monitoring of dabigatran etexilate. Thromb Haemost 2012; 107 (5) 985-997
• 22 Halbmayer WM, Weigel G, Quehenberger P , et al. Interference of the new oral anticoagulant dabigatran with frequently used coagulation tests. Clin Chem Lab Med 2012; 50 (9) 1601-1605
• 23 Dager WE, Gosselin RC, Kitchen S, Dwyre D. Dabigatran effects on the international normalized ratio, activated partial thromboplastin time, thrombin time, and fibrinogen: a multicenter, in vitro study. Ann Pharmacother 2012; 46 (12) 1627-1636
• 24 Samama MM, Guinet C, Le Flem L, Ninin E, Debue JM. Measurement of dabigatran and rivaroxaban in primary prevention of venous thromboembolism in 106 patients, who have undergone major orthopedic surgery: an observational study. J Thromb Thrombolysis 2013; 35 (2) 140-146
• 25 Helin TA, Pakkanen A, Lassila R, Joutsi-Korhonen L. Laboratory assessment of novel oral anticoagulants: method suitability and variability between coagulation laboratories. Clin Chem 2013; 59 (5) 807-814
• 26 Hawes EM, Deal AM, Funk-Adcock D , et al. Performance of coagulation tests in patients on therapeutic doses of dabigatran: a cross-sectional pharmacodynamic study based on peak and trough plasma levels. J Thromb Haemost 2013; 11 (8) 1493-1502
• 27 Douxfils J, Dogné JM, Mullier F , et al. Comparison of calibrated dilute thrombin time and aPTT tests with LC-MS/MS for the therapeutic monitoring of patients treated with dabigatran etexilate. Thromb Haemost 2013; 110 (3) 543-549
• 28 Hapgood G, Butler J, Malan E, Chunilal S, Tran H. The effect of dabigatran on the activated partial thromboplastin time and thrombin time as determined by the Hemoclot thrombin inhibitor assay in patient plasma samples. Thromb Haemost 2013; 110 (2) 308-315
• 29 Antovic JP, Skeppholm M, Eintrei J , et al. Evaluation of coagulation assays versus LC-MS/MS for determinations of dabigatran concentrations in plasma. Eur J Clin Pharmacol 2013; 69 (11) 1875-1881
• 30 Herrmann R, Thom J, Wood A, Phillips M, Muhammad S, Baker R. Thrombin generation using the calibrated automated thrombinoscope to assess reversibility of dabigatran and rivaroxaban. Thromb Haemost 2014; 111 (5) 989-995
• 31 Eller T, Busse J, Dittrich M , et al. Dabigatran, rivaroxaban, apixaban, argatroban and fondaparinux and their effects on coagulation POC and platelet function tests. Clin Chem Lab Med 2014; 52 (6) 835-844
• 32 Chin PK, Wright DF, Patterson DM, Doogue MP, Begg EJ. A proposal for dose-adjustment of dabigatran etexilate in atrial fibrillation guided by thrombin time. Br J Clin Pharmacol 2014; 78 (3) 599-609
• 33 Stang L, Nahirniak S, Butcher K, Szkotak AJ. Dabigatran assessment in patients with acute complications using routine coagulation assays. Blood Coagul Fibrinolysis 2014; 25 (5) 426-434
• 34 Lind SE, Boyle ME, Fisher S, Ishimoto J, Trujillo TC, Kiser TH. Comparison of the aPTT with alternative tests for monitoring direct thrombin inhibitors in patient samples. Am J Clin Pathol 2014; 141 (5) 665-674
• 35 Schmitz EM, Boonen K, van den Heuvel DJ , et al. Determination of dabigatran, rivaroxaban and apixaban by ultra-performance liquid chromatography - tandem mass spectrometry (UPLC-MS/MS) and coagulation assays for therapy monitoring of novel direct oral anticoagulants. J Thromb Haemost 2014; 12 (10) 1636-1646
• 36 van Ryn J, Grottke O, Spronk H. Measurement of dabigatran in standardly used clinical assays, whole blood viscoelastic coagulation, and thrombin generation assays. Clin Lab Med 2014; 34 (3) 479-501
• 37 Skeppholm M, Hjemdahl P, Antovic JP , et al. On the monitoring of dabigatran treatment in “real life” patients with atrial fibrillation. Thromb Res 2014; 134 (4) 783-789
• 38 Czubek U, Góralczyk T, Zalewski J, Undas A. Monitoring of anticoagulant effects of dabigatran in everyday practice: first experience in 32 Polish patients. Pol Arch Med Wewn 2014; 124 (9) 487-489
• 39 Van Blerk M, Bailleul E, Chatelain B , et al. Influence of dabigatran and rivaroxaban on routine coagulation assays. A nationwide Belgian survey. Thromb Haemost 2015; 113 (1) 154-164
• 40 Martinuzzo ME, Barrera LH, D'adamo MA, Otaso JC, Gimenez MI, Oyhamburu J. Frequent false-positive results of lupus anticoagulant tests in plasmas of patients receiving the new oral anticoagulants and enoxaparin. Int J Lab Hematol 2014; 36: 144-150
• 41 Bonar R, Favaloro EJ, Marsden K ; RCPAQAP Haematology Haemostasis Committee. Dabigatran Special Exercise Report. Issued April, 2014. RCPA Quality Assurance Programs Pty Limited. St Leonards, NSW, Australia
• 42 Stangier J, Feuring M. Using the HEMOCLOT direct thrombin inhibitor assay to determine plasma concentrations of dabigatran. Blood Coagul Fibrinolysis 2012; 23 (2) 138-143
• 43 Avecilla ST, Ferrell C, Chandler WL, Reyes M. Plasma-diluted thrombin time to measure dabigatran concentrations during dabigatran etexilate therapy. Am J Clin Pathol 2012; 137 (4) 572-574
• 44 Samoš M, Stančiaková L, Ivanková J , et al. Monitoring of dabigatran therapy using Hemoclot(®) Thrombin Inhibitor assay in patients with atrial fibrillation. J Thromb Thrombolysis 2015; 39 (1) 95-100
• 45 Visino F, Zaccaria F, Semeraro N, Colucci M. A modified prothrombin time to measure the anticoagulant activity of dabigatran. Thromb Res 2014; 134 (6) 1368-1369
• 46 Gosselin R, Hawes E, Moll S, Adcock D. Performance of various laboratory assays in the measurement of dabigatran in patients receiving therapeutic doses: a prospective study based on peak and trough plasma levels. Am J Clin Pathol 2014; 141 (2) 262-267
• 47 Gosselin RC, Dwyre DM, Dager WE. Measuring dabigatran concentrations using a chromogenic ecarin clotting time assay. Ann Pharmacother 2013; 47 (12) 1635-1640
• 48 Tsutsumi Y, Shimono J, Ohhigashi H, Ito S, Shiratori S, Teshima T. Analysis of the influence of dabigatran on coagulation factors and inhibitors. Int J Lab Hematol 2014; ; doi: 10.1111/ijlh.12270
• 49 Exner T, Ellwood L, Rubie J, Barancewicz A. Testing for new oral anticoagulants with LA-resistant Russells viper venom reagents. An in vitro study. Thromb Haemost 2013; 109 (4) 762-765
• 50 Khoo TL, Weatherburn C, Kershaw G, Reddel CJ, Curnow J, Dunkley S. The use of FEIBA® in the correction of coagulation abnormalities induced by dabigatran. Int J Lab Hematol 2013; 35 (2) 222-224
• 51 Solbeck S, Meyer MA, Johansson PI , et al. Monitoring of dabigatran anticoagulation and its reversal in vitro by thrombelastography. Int J Cardiol 2014; 176 (3) 794-799
• 52 Xu Y, Wu W, Wang L , et al. Differential profiles of thrombin inhibitors (heparin, hirudin, bivalirudin, and dabigatran) in the thrombin generation assay and thromboelastography in vitro. Blood Coagul Fibrinolysis 2013; 24 (3) 332-338
• 53 Hosokawa K, Ohnishi T, Sameshima H , et al. Comparative evaluation of direct thrombin and factor Xa inhibitors with antiplatelet agents under flow and static conditions: an in vitro flow chamber model. PLoS ONE 2014; 9 (1) e86491
• 54 Dale BJ, Ginsberg JS, Johnston M, Hirsh J, Weitz JI, Eikelboom JW. Comparison of the effects of apixaban and rivaroxaban on prothrombin and activated partial thromboplastin times using various reagents. J Thromb Haemost 2014; 12 (11) 1810-1815
• 55 Bonar R, Favaloro EJ, Marsden K ; RCPAQAP Haematology Haemostasis Committee. Apixaban and Rivaroxaban Trial Report. Issued December, 2014. RCPA Quality Assurance Programs Pty Limited. St Leonards, NSW, Australia
• 56 Samama MM, Martinoli JL, LeFlem L , et al. Assessment of laboratory assays to measure rivaroxaban—an oral, direct factor Xa inhibitor. Thromb Haemost 2010; 103 (4) 815-825
• 57 Francart SJ, Hawes EM, Deal AM , et al. Performance of coagulation tests in patients on therapeutic doses of rivaroxaban. A cross-sectional pharmacodynamic study based on peak and trough plasma levels. Thromb Haemost 2014; 111 (6) 1133-1140
• 58 Arachchillage DR, Efthymiou M, Lawrie AS, Machin SJ, Mackie IJ, Cohen H. Comparative sensitivity of commonly used thromboplastins to ex vivo therapeutic rivaroxaban levels. Thromb Haemost 2014; 112 (2) 421-423
• 59 Tripodi A, Chantarangkul V, Guinet C, Samama MM. The International Normalized Ratio calibrated for rivaroxaban has the potential to normalize prothrombin time results for rivaroxaban-treated patients: results of an in vitro study. J Thromb Haemost 2011; 9 (1) 226-228
• 60 Hillarp A, Baghaei F, Fagerberg Blixter I , et al. Effects of the oral, direct factor Xa inhibitor rivaroxaban on commonly used coagulation assays. J Thromb Haemost 2011; 9 (1) 133-139
• 61 Douxfils J, Mullier F, Loosen C, Chatelain C, Chatelain B, Dogné JM. Assessment of the impact of rivaroxaban on coagulation assays: laboratory recommendations for the monitoring of rivaroxaban and review of the literature. Thromb Res 2012; 130 (6) 956-966
• 62 Linkins LA, Moffat K. Monitoring the anticoagulant effect after a massive rivaroxaban overdose. J Thromb Haemost 2014; 12 (9) 1570-1571
• 63 Altman R, Gonzalez CD. Simple and rapid assay for effect of the new oral anticoagulant (NOAC) rivaroxaban: preliminary results support further tests with all NOACs. Thromb J 2014; 12 (1) 7
• 64 Asmis LM, Alberio L, Angelillo-Scherrer A , et al. Rivaroxaban: Quantification by anti-FXa assay and influence on coagulation tests: a study in 9 Swiss laboratories. Thromb Res 2012; 129 (4) 492-498
• 65 Attard C, Monagle P, Kubitza D, Ignjatovic V. The in vitro anticoagulant effect of rivaroxaban in children. Thromb Res 2012; 130 (5) 804-807
• 66 Harenberg J, Marx S, Krämer R, Giese C, Weiss C. Determination of an international sensitivity index of thromboplastin reagents using a WHO thromboplastin as calibrator for plasma spiked with rivaroxaban. Blood Coagul Fibrinolysis 2011; 22 (8) 637-641
• 67 Samama MM, Contant G, Spiro TE , et al; Rivaroxaban Prothrombin Time Field Trial Laboratories. Evaluation of the prothrombin time for measuring rivaroxaban plasma concentrations using calibrators and controls: results of a multicenter field trial. Clin Appl Thromb Hemost 2012; 18 (2) 150-158
• 68 Molenaar PJ, Dinkelaar J, Leyte A. Measuring Rivaroxaban in a clinical laboratory setting, using common coagulation assays, Xa inhibition and thrombin generation. Clin Chem Lab Med 2012; 50 (10) 1799-1807
• 69 Harenberg J, Erdle S, Marx S, Krämer R. Determination of rivaroxaban in human plasma samples. Semin Thromb Hemost 2012; 38 (2) 178-184
• 70 Harder S, Parisius J, Picard-Willems B. Monitoring direct FXa-inhibitors and fondaparinux by Prothrombinase-induced Clotting Time (PiCT): relation to FXa-activity and influence of assay modifications. Thromb Res 2008; 123 (2) 396-403
• 71 Kluft C, Meijer P, Kret R, Burggraaf J. Preincubation in the Prothrombinase-induced Clotting Time test (PiCT) is necessary for in vitro evaluation of fondaparinux and to be avoided for the reversible, direct factor Xa inhibitor, rivaroxaban. Int J Lab Hematol 2013; 35 (4) 379-384
• 72 Gerotziafas GT, Baccouche H, Sassi M , et al. Optimisation of the assays for the measurement of clotting factor activity in the presence of rivaroxaban. Thromb Res 2012; 129 (1) 101-103
• 73 Merriman E, Kaplan Z, Butler J, Malan E, Gan E, Tran H. Rivaroxaban and false positive lupus anticoagulant testing. Thromb Haemost 2011; 105 (2) 385-386
• 74 Gosselin RC, Adcock Funk DM, Taylor JM , et al. Comparison of anti-Xa and dilute Russell viper venom time assays in quantifying drug levels in patients on therapeutic doses of rivaroxaban. Arch Pathol Lab Med 2014; 138 (12) 1680-1684
• 75 Samama MM, Contant G, Spiro TE , et al; Rivaroxaban Anti-Factor Xa Chromogenic Assay Field Trial Laboratories. Evaluation of the anti-factor Xa chromogenic assay for the measurement of rivaroxaban plasma concentrations using calibrators and controls. Thromb Haemost 2012; 107 (2) 379-387
• 76 Kubitza D, Becka M, Voith B, Zuehlsdorf M, Wensing G. Safety, pharmacodynamics, and pharmacokinetics of single doses of BAY 59-7939, an oral, direct factor Xa inhibitor. Clin Pharmacol Ther 2005; 78 (4) 412-421
• 77 Samama MM, Amiral J, Guinet C, Perzborn E, Depasse F. An optimised, rapid chromogenic assay, specific for measuring direct factor Xa inhibitors (rivaroxaban) in plasma. Thromb Haemost 2010; 104 (5) 1078-1079
• 78 Harenberg J, Krämer R, Giese C, Marx S, Weiss C, Wehling M. Determination of rivaroxaban by different factor Xa specific chromogenic substrate assays: reduction of interassay variability. J Thromb Thrombolysis 2011; 32 (3) 267-271
• 79 Mani H, Rohde G, Stratmann G , et al. Accurate determination of rivaroxaban levels requires different calibrator sets but not addition of antithrombin. Thromb Haemost 2012; 108 (1) 191-198
• 80 Douxfils J, Tamigniau A, Chatelain B , et al. Comparison of calibrated chromogenic anti-Xa assay and PT tests with LC-MS/MS for the therapeutic monitoring of patients treated with rivaroxaban. Thromb Haemost 2013; 110 (4) 723-731
• 81 Adelmann D, Wiegele M, Wohlgemuth RK , et al. Measuring the activity of apixaban and rivaroxaban with rotational thromboelastometry. Thromb Res 2014; 134 (4) 918-923
• 82 Levi M, Moore KT, Castillejos CF , et al. Comparison of three-factor and four-factor prothrombin complex concentrates regarding reversal of the anticoagulant effects of rivaroxaban in healthy volunteers. J Thromb Haemost 2014; 12 (9) 1428-1436
• 83 Perzborn E, Heitmeier S, Laux V, Buchmüller A. Reversal of rivaroxaban-induced anticoagulation with prothrombin complex concentrate, activated prothrombin complex concentrate and recombinant activated factor VII in vitro. Thromb Res 2014; 133 (4) 671-681
• 84 Casutt M, Konrad C, Schuepfer G. Effect of rivaroxaban on blood coagulation using the viscoelastic coagulation test ROTEM™. Anaesthesist 2012; 61 (11) 948-953
• 85 Bowry R, Fraser S, Archeval-Lao JM , et al. Thrombelastography detects the anticoagulant effect of rivaroxaban in patients with stroke. Stroke 2014; 45 (3) 880-883
• 86 Becker RC, Alexander JH, Newby LK , et al. Effect of apixaban, an oral and direct factor Xa inhibitor, on coagulation activity biomarkers following acute coronary syndrome. Thromb Haemost 2010; 104 (5) 976-983
• 87 Yamahira N, Frost C, Fukase H , et al. Safety, tolerability, pharmacokinetics, and pharmacodynamics of multiple doses of apixaban in healthy Japanese male subjects. Int J Clin Pharmacol Ther 2014; 52 (7) 564-573
• 88 Douxfils J, Chatelain C, Chatelain B, Dogné JM, Mullier F. Impact of apixaban on routine and specific coagulation assays: a practical laboratory guide. Thromb Haemost 2013; 110 (2) 283-294
• 89 Gouin-Thibault I, Flaujac C, Delavenne X , et al. Assessment of apixaban plasma levels by laboratory tests: suitability of three anti-Xa assays. A multicentre French GEHT study. Thromb Haemost 2014; 111 (2) 240-248
• 90 Hillarp A, Gustafsson KM, Faxälv L , et al. Effects of the oral, direct factor Xa inhibitor apixaban on routine coagulation assays and anti-FXa assays. J Thromb Haemost 2014; 12 (9) 1545-1553
• 91 Harenberg J, Du S, Weiss C, Krämer R, Hoppensteadt D, Walenga J ; working party: methods to determine apixaban of the Subcommittee on Control of Anticoagulation of the International Society of Thrombosis and Haemostasis. Report of the Subcommittee on Control of Anticoagulation on the determination of the anticoagulant effects of apixaban: communication from the SSC of the ISTH. J Thromb Haemost 2014; 12 (5) 801-804
• 92 Tripodi A, Padovan L, Testa S , et al. How the direct oral anticoagulant apixaban affects hemostatic parameters. Results of a multicenter multiplatform study. Clin Chem Lab Med 2015; 53 (2) 265-273
• 93 Barrett YC, Wang Z, Knabb RM. A novel prothrombin time assay for assessing the anticoagulant activity of oral factor Xa inhibitors. Clin Appl Thromb Hemost 2013; 19 (5) 522-528
• 94 Frost C, Nepal S, Wang J , et al. Safety, pharmacokinetics and pharmacodynamics of multiple oral doses of apixaban, a factor Xa inhibitor, in healthy subjects. Br J Clin Pharmacol 2013; 76 (5) 776-786
• 95 Upreti VV, Wang J, Barrett YC , et al. Effect of extremes of body weight on the pharmacokinetics, pharmacodynamics, safety and tolerability of apixaban in healthy subjects. Br J Clin Pharmacol 2013; 76 (6) 908-916
• 96 Barrett YC, Wang Z, Frost C, Shenker A. Clinical laboratory measurement of direct factor Xa inhibitors: anti-Xa assay is preferable to prothrombin time assay. Thromb Haemost 2010; 104 (6) 1263-1271
• 97 Becker RC, Yang H, Barrett Y , et al. Chromogenic laboratory assays to measure the factor Xa-inhibiting properties of apixaban—an oral, direct and selective factor Xa inhibitor. J Thromb Thrombolysis 2011; 32 (2) 183-187
• 98 Frost C, Wang J, Nepal S , et al. Apixaban, an oral, direct factor Xa inhibitor: single dose safety, pharmacokinetics, pharmacodynamics and food effect in healthy subjects. Br J Clin Pharmacol 2013; 75 (2) 476-487
• 99 Ogata K, Mendell-Harary J, Tachibana M , et al. Clinical safety, tolerability, pharmacokinetics, and pharmacodynamics of the novel factor Xa inhibitor edoxaban in healthy volunteers. J Clin Pharmacol 2010; 50 (7) 743-753
• 100 Favaloro EJ, Plebani M, Lippi G. Regulation in hemostasis and thrombosis: part I-in vitro diagnostics. Semin Thromb Hemost 2013; 39 (3) 235-249
• 101 Lippi G, Mattiuzzi C, Favaloro EJ. Thrombophilia testing in patients taking direct oral anticoagulants. Handle with care. Diagnosis 2014; 1 (4) 311-312
• 102 Gómez-Outes A, Suárez-Gea ML, Lecumberri R, Terleira-Fernandez AI, Vargas-Castrillon E. Specific antidotes in development for reversal of novel anticoagulants: a review. Recent Pat Cardiovasc Drug Discov 2014; 9 (1) 2-10
• 103 Zahir H, Brown KS, Vandell AG , et al. Edoxaban effects on bleeding following punch biopsy and reversal by a 4-factor prothrombin complex concentrate. Circulation 2015; 131 (1) 82-90
• 104 Halim AB, Samama MM, Mendell J. Ex vivo reversal of the anticoagulant effects of edoxaban. Thromb Res 2014; 134 (4) 909-913
• 105 Fukuda T, Honda Y, Kamisato C, Morishima Y, Shibano T. Reversal of anticoagulant effects of edoxaban, an oral, direct factor Xa inhibitor, with haemostatic agents. Thromb Haemost 2012; 107 (2) 253-259
• 106 Dinkelaar J, Molenaar PJ, Ninivaggi M, de Laat B, Brinkman HJ, Leyte A. In vitro assessment, using thrombin generation, of the applicability of prothrombin complex concentrate as an antidote for Rivaroxaban. J Thromb Haemost 2013; 11 (6) 1111-1118
• 107 Sølbeck S, Nilsson CU, Engström M, Ostrowski SR, Johansson PI. Dabigatran and its reversal with recombinant factor VIIa and prothrombin complex concentrate: a Sonoclot in vitro study. Scand J Clin Lab Invest 2014; 74 (7) 591-598
• 108 Körber MK, Langer E, Ziemer S, Perzborn E, Gericke C, Heymann Cv. Measurement and reversal of prophylactic and therapeutic peak levels of rivaroxaban: an in vitro study. Clin Appl Thromb Hemost 2014; 20 (7) 735-740
• 109 Eerenberg ES, Kamphuisen PW, Sijpkens MK, Meijers JC, Buller HR, Levi M. Reversal of rivaroxaban and dabigatran by prothrombin complex concentrate: a randomized, placebo-controlled, crossover study in healthy subjects. Circulation 2011; 124 (14) 1573-1579
• 110 Dinkelaar J, Patiwael S, Harenberg J, Leyte A, Brinkman HJ. Global coagulation tests: their applicability for measuring direct factor Xa- and thrombin inhibition and reversal of anticoagulation by prothrombin complex concentrate. Clin Chem Lab Med 2014; 52 (11) 1615-1623
• 111 Davis PK, Musunuru H, Walsh M, Mitra R, Ploplis V, Castellino FJ. The ex vivo reversibility of dabigatran-induced whole-blood coagulopathy as monitored by thromboelastography: mechanistic implications for clinical medicine. Thromb Haemost 2012; 108 (3) 586-588
• 112 Marlu R, Hodaj E, Paris A, Albaladejo P, Cracowski JL, Pernod G. Effect of non-specific reversal agents on anticoagulant activity of dabigatran and rivaroxaban: a randomised crossover ex vivo study in healthy volunteers. Thromb Haemost 2012; 108 (2) 217-224
• 113 Di Minno A, Spadarella G, Prisco D, Franchini M, Lupoli R, Di Minno MN. Clinical judgment when using coagulation tests during direct oral anticoagulant treatment: a concise review. Semin Thromb Hemost 2013; 39 (7) 840-846
• 114 Favaloro EJ, Bonar R, Butler J, Marsden K. Laboratory testing for the new oral anticoagulants: a review of current practice. Pathology 2013; 45 (4) 435-437
• 115 Harenberg J, Krämer S, Du S, Weiss C, Krämer R. Concept of a point of care test to detect new oral anticoagulants in urine samples. Thromb J 2013; 11 (1) 15
• 116 Harenberg J, Du S, Krämer S , et al. Novel methods for assessing oral direct factor Xa and thrombin inhibitors: use of point-of-care testing and urine samples. Semin Thromb Hemost 2013; 39 (1) 66-71
• 117 Harenberg J, Kraemer R. Measurement of the new anticoagulants. Thromb Res 2012; 129 (Suppl. 01) S106-S113
• 118 Harenberg J, Krämer S, Du S , et al. Measurement of rivaroxaban and apixaban in serum samples of patients. Eur J Clin Invest 2014; 44 (8) 743-752
• 119 Harenberg J, Kraemer S, Du S , et al. Determination of direct oral anticoagulants from human serum samples. Semin Thromb Hemost 2014; 40 (1) 129-134