Measurement of Direct Anti-IIa Activity of Dabigatran (Reference ) Notice of Assessment

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1 Measurement of Direct Anti-IIa Activity of Dabigatran (Reference ) Notice of Assessment December 2013 DISCLAIMER: This document was originally drafted in French by the Institut national d'excellence en santé et en services sociaux (INESSS), and that version can be consulted at te_anti-iia_direct_du_dabigatran.pdf. It was translated into English by the Canadian Agency for Drugs and Technologies in Health (CADTH) with INESSS s permission. INESSS assumes no responsibility with regard to the quality or accuracy of the translation. While CADTH has taken care in the translation of the document to ensure it accurately represents the content of the original document, CADTH does not make any guarantee to that effect. CADTH is not responsible for any errors or omissions or injury, loss, or damage arising from or relating to the use (or misuse) of any information, statements, or conclusions contained in or implied by the information in this document, the original document, or in any of the source documentation.

2 1 GENERAL INFORMATION 1.1 Requestor: CHUM 1.2 Application Sent to MSSS: June 18, Application Received by INESSS: July 1, Notice Issued: October 31, 2013 Note: This notice is based on the scientific and commercial information (submitted by the requestor[s]) and on a complementary review of the literature according to the data available at the time that this test was assessed by INESSS. 2 TECHNOLOGY, COMPANY, AND LICENCE(S) 2.1 Name of the Technology The requestor uses the commercially available Hemoclot Thrombin Inhibitors kit. This technology is useful for the quantitative measurement of dabigatran and other direct thrombin inhibitors (DTIs) (hirudin and argatroban) and is based on the inhibition of a constant and defined quantity of thrombin. The requestor also uses the Dabigatran Plasma Calibrator and Dabigatran Control Plasma kits designed for calibration and quality control, respectively. 2.2 Brief Description of the Technology, and Technical and Clinical Specifications Dabigatran is an oral anticoagulant approved by Health Canada in October 2010 for the prevention of cerebrovascular accidents and systemic embolisms in adults with atrial fibrillation for whom systemic anticoagulation has been indicated. It has also been indicated [APhC, 2013], since 2008, for the prevention of venous thromboembolism in patients following elective total hip and total knee arthroplasty [APhC, 2013]. Dabigatran is a potent, competitive, and reversible direct thrombin inhibitor [APhC, 2013; Stangier and Clemens, 2009]. As with all anticoagulants, dabigatran is associated with hemorrhage: 2,367 reports of severe hemorrhage and 542 deaths in 2011, based on statistics by the Food and Drug Administration (FDA) in the United States. The risk of hemorrage may be limited by screening for certain conditions such as renal insufficiency (even moderate), old age, or extreme body weight [Prescrire, 2013; ISMP, 2012]. The concomitant use of platelet aggregation inhibitors, such as aspirin, nonsteroidal anti-inflammatory drugs, and numerous cardiologic drugs, also increases the risk of hemorrhage [Prescrire, 2013]. In any event, dabigatran assays are generally not required, except in specific circumstances, such as in preparation for surgery or for invasive procedures [Garcia et al., 2013]. Clinicians might consider monitoring the effect of dabigatran in other situations. Level of adherence to treatment, detection of overdose or underdose, accumulation of blood, or identification of the cause of bleeding are a few examples [Chin et al., 2013; Fawole et al., 2013; Garcia et al., 2013; Tripodi, 2013]. The Hemoclot Thrombin Inhibitors technology is a modified version of thrombin time and involves diluted plasma samples [Stangier and Feuring, 2012; van Ryn et al., 2010]. The clotting time measured is directly related to the concentration of assayed DTI in the tested plasma [HYPHEN, 2010]. The method may be automated for various analyzers on the market. In fact, an adapted method is given on the site of the wholesaler, ANIARA, for the BCS XP automated analyzer used by the requestor. 1

3 Calibration plasma samples with increasing concentrations of dabigatran must be used to calibrate the assay method (Dabigatran Plasma Calibrator kit)[hyphen, 2012a]. Adapted control plasma samples, titrated for the assayed DTI, can be used to validate the calibration curve and the homogeneous reactivity of the assay in different series for the same lot of reagents (Dabigatran Control Plasma kit)[hyphen, 2012b]. Figure 1: Assay with the Hemoclot Thrombin Inhibitors kit Source: Company or Developer: HYPHEN BioMed, Neuville-sur-Oise (France). 2.4 Licence: Not applicable. 2.5 Patent, If Any: Not applicable. 2.6 Approval Status (Health Canada, FDA) The Hemoclot Thrombin Inhibitors kit received approval (number 84966) from Health Canada January 24, This kit is for in vitro diagnostic use only. 2.7 Weighted Value:

4 3 CLINICAL INDICATIONS, PRACTICE SETTINGS, AND TESTING PROCEDURES 3.1 Targeted Patient Group Patients targeted by the requestor are those experiencing severe bleeding such as intracerebral hemorrhage and patients taking the anticoagulant dabigatran who must undergo emergency surgery. 3.2 Targeted Disease(s) The test under consideration does not target a specific disease but rather the therapeutic monitoring of patients treated with dabigatran who meet the criteria set out in 3.1. The predictable pharmacokinetic and pharmacodynamic profiles of dabigatran make it an alternative to warfarin. However, as there is very little evidence on the preferred method of intervention to manage major or clinically significant bleeding in patients taking dabigatran, and as there is no specific antidote to reverse its anticoagulant effect, many physicians are reluctant to prescribe it [Fawole et al., 2013; Miyares and Davis, 2012]. 3.3 Number of Patients Targeted In June 2012, the requestor anticipated a provincial volume of approximately 200 tests over the next 3 years. This number could increase with the projected increase in dabigatran prescriptions. Based on the analyses performed at INESSS, the number of individuals taking dabigatran and covered by the public drug insurance plan was 13,191 and 20,206 in 2011 and 2012 respectively (results not published). This number reached 19,321 after the first 7 months in The number of tests carried out could be higher than that anticipated by the requestor due to the increase in dabigatran prescriptions and to uses not limited to particular situations such as preparation for surgery or invasive procedures. 3.4 Medical Specialties Involved (and Other Professions, If Any) The main medical specialties involved are hematology, surgery, emergency medicine and family medicine. In all likelihood, dental surgeons and pharmacists also will prescribe the quantitative measurement of dabigatran. 3.5 Testing Procedure Blood (9 volumes) samples must be drawn into trisodium citrate mol/l (1 volume) [HYPHEN, 2010]. Plasma is obtained after 20 minutes of centrifugation at 2,500 g 26. The citrated plasma must be used within 8 hours if it is maintained at the ambient temperature of the laboratory (18 C to 25 C). It may be used within 24 hours if it is maintained at 2 C to 8 C. The citrated plasma may be stored for up to 6 months until use if it is frozen at -20 C or lower. All suspect samples (icteric, hemolyzed, lipemic, etc.) must be discarded. Stangier et al. [2012] showed that plasma samples containing dabigatran were stable for 24 hours at room temperature and at 4 C. Moreover, the samples did not show any change in clotting time after one to four freezing and thawing cycles [Stangier and Feurig, 2012]. The assay is calibrated with the DTI used [HYPHEN, 2012a, 2010]. The Hemoclot Thrombin Inhibitors kit is currently validated for assaying hirudin (lepirudin/refludan ), dabigatran, and argatroban. The assay working range for dabigatran is 0.05 mcg/ml to 0.50 mcg/ml with the low-range (usual) protocol. 26. The resulting acceleration, written as g, is a function of the rate of rotation and the distance from the axis of rotation. It is expressed by the following formula: g = w 2 r = 1, r n 2, where w = angular velocity (rad/s); r = distance from the axis of rotation; n = number of revolutions per minute (rpm). 3

5 The calibration plasma samples from the Dabigatran Plasma Calibrator kit can be used to establish a calibration curve for the measurement of dabigatran in plasma with the anti-iia method. When the Hemoclot Thrombin Inhibitors kit is used according to the low-range protocol, the test is linear up to approximately 500 ng/ml with the manual method or STA-R. The resulting calibration curve covers the usual concentrations observed with dabigatran treatment. Control plasma samples from the Dabigatran Control Plasma kit (levels 1 and 2) allow quality control of the calibration curve for the measurement of dabigatran in plasma [HYPHEN, 2012b, 2010], through validation of the calibration curve for each series of measurements carried out with the same lot of reagents. If results obtained from the controls are outside of the acceptable range, the series of measurements is therefore not valid and must be redone. All parameters of the system must be controlled before the series is repeated. The measured DTI concentration must be analyzed in terms of the regimen used and the clinical context of the patient [HYPHEN, 2012a]. In case of an unexpected result, the concentration must be verified by performing a new test and, if required, by using another method to evaluate the hypocoagulability state of the patient. 4 TECHNOLOGY BACKGROUND 4.1 Nature of the Diagnostic Technology: Unique. 4.2 Brief Description of the Current Technological Context Various coagulation tests were assessed in young and older volunteers and in patients undergoing hip arthroplasty or with atrial fibrillation [Antovic et al., 2013; Hapgood et al., 2013; Samama et al., 2013; Stangier and Clemens, 2009]. The assessments showed that dabigatran interferes with the parameters of routine coagulation tests [Garcia et al., 2013; Tripodi, 2013; Douxfils et al., 2012; Girard-Desbiens et al., 2013]. The international normalized ratio (INR), which represents the standardized result of prothrombin time (PT), is not sufficiently sensitive, and therefore not useful in the assessment of the anticoagulant activity of dabigatran [APhC, 2013; Garcia et al., 2013; Douxfils et al., 2012]. The variation in sensitivity observed among laboratories for activated cephalin time (ACT, equivalent of aptt) and the overly high sensitivity of thrombin time (TT) to dabigatran make it difficult to formulate general recommendations for the two routine tests [Girard-Desbiens et al., 2013]. Nevertheless, ACT and TT have some clinical usefulness in the qualitative measurement of dabigatran [Garcia et al., 2013; Hawes et al., 2013; Miyares and Davis, 2012; Stangier and Clemens, 2009]. ACT is useful in detecting high concentrations of dabigatran, and TT can detect low concentrations of the drug, as illustrated further on. At present, Hemoclot Thrombin Inhibitors is among the most sensitive tests used to determine dabigatran concentrations [Douxfils et al., 2012]. Moreover, this simple-to-use and automatable test shows excellent reproducibility and a linear correlation for all doses [Douxfils et al., 2012; Stangier and Feuring, 2012]. For these reasons, some consider it the reference test for the measurement of dabigatran [Hapgood et al., 2013; Douxfils et al., 2012]. Some authors suggest using ACT prior to Hemoclot Thrombin Inhibitors as a detection test to assess the risk of overdose [Douxfils et al., 2012; Messier and Lapierre, 2011], for example, in a patient with a hemorrhage [Miyares and Davis, 2012; Australian Government, 2011]. An ACT of more than 80 seconds just prior to the next dose would therefore be associated with a higher risk of bleeding [Messier and Lapierre, 2011]. However, Hemoclot Thrombin Inhibitors performs poorly at concentrations lower than 50 ng/ml. The limitations specified by the manufacturer for quantification (100 ng/ml) and detection (30 ng/ml) are 4

6 greater than those obtained during a recent study: 53 ng/ml and 22 ng/ml, respectively [Douxfils et al., 2013]. Two other tests are available to measure the effect of dabigatran. Ecarin clotting time (ECT) is a specific test for thrombin formation. The test directly measures the activity of DTIs [van Ryn et al., 2010]. Although ECT has been recommended by some authors for the measurement of dabigatran [Tripodi, 2013; Miyares and Davis, 2012], its results are influenced by plasma levels of fibrinogen and thrombin [Fawole et al., 2013]. The ecarin chromogenic assay (ECA) is an improvement on ecarin clotting time (current method). This test is not affected by levels of fibrinogen or prothrombin and also has the advantage of being automatable [Fawole et al., 2013]. Ecarin chromogenic assays generally are not used in clinical settings to assess the effects of DTIs. The Biophen DTI commercial kit by HYPHEN BioMed, an assay that measures DTIs using a chromogenic method, is intended for in vitro research use only [HYPHEN, 2008]. Moreover, the manufacturer, ANIARA, does not recommend any particular kit to calibrate the Biophen DTI test, as opposed to what is done for Hemoclot Thrombin Inhibitors [HYPHEN, 2010, 2008]. Figure 2: Possible Test Use Based on Clinical Situations Source: [Hawes et al., 2013] Abbreviations: ACT = activated clotting time; aptt = activated partial thromboplastin time; dtt = diluted thrombin time (dtt = HTI); ECA = ecarin chromogenic assay; ECT = ecarin clotting time; TCT = TT; PT = prothrombin time. 4.3 Brief Description of the Advantages Cited for the New Technology The new test allows dabigatran to be measured in emergency situations such as emergency surgery that cannot be postponed or in a case of hemorrhage to determine the residual quantity of dabigatran. The time interval between the administration of dabigatran and blood sampling for the assay is important, since the start and end of the action of the new oral anticoagulants is relatively brief [Garcia et al., 2013; Tripodi, 2013]. Consequently, clinicians must be cautious in their interpretation of laboratory results, since the data may not accurately reflect the in vivo situation[garcia et al., 2013; Tripodi, 2013]. Emergency situations such as hemorrhage or thrombosis provide few options in terms of the opportune time for blood sampling and dabigatran measurement [Tripodi, 2013]. Clinicians will require training on how to measure dabigatran at the appropriate time and how to correctly interpret the results of the laboratory tests [Garcia et al., 2013]. 5

7 4.4 Cost of Technology and Options: Not assessed. 5 EVIDENCE 5.1 Clinical Relevance Other Tests Replaced No other currently available commercial test allows a valid and precise quantitative measurement of dabigatran in a clinical environment Diagnostic or Prognostic Value: Not applicable Therapeutic Value Dabigatran assays in asymptomatic individuals on chronic stable therapy may involve some risk if clinicians decide to deviate from the regimen recognized as effective [Garcia et al., 2013]. Indeed, some clinicians may overestimate the importance of a measurement that is slightly higher or lower than the standard reference range. Although pharmacokinetic studies have established an expected range for dabigatran concentrations, the range does not necessarily define the limit above which the risk of bleeding or thrombosis will significantly increase for an individual. Unlike warfarin, for which the relation between the INR and concentrations outside the therapeutic range are more clearly understood, the clinical importance of coagulation test results outside the therapeutic range is not yet known for dabigatran. Moreover, the interpretation of laboratory results for dabigatran must take into account when the sample was collected, which is not the case for IRN measurements for individuals treated with warfarin. Therefore, even if an evidence-based regimen adjustment strategy were used, the potential for erroneous interpretation (or adverse effect) following only one measurement would be significant [Garcia et al., 2013]. 5.2 Clinical Validity No studies on the clinical validity of dabigatran assays were identified. 5.3 Analytical (or Technical) Validity PARAMETER PRESENCE ABSENCE NOT APPLICABLE Repeatability Reproducibility Analytical sensitivity x x x Analytical specificity X Matrix effect x Concordance x Correlation between test and comparator x Precision The manufacturer of the Hemoclot Thrombin Inhibitors kit estimates the intra-assay variability at 2.2% and the inter-assay variability at 5.3% based on the coefficient of variation (CV) [HYPHEN, 2010]. At dabigatran concentrations of 100, 500 and 1,500 nmol/l, total assay precision (within device or laboratory) in terms of CV ranged from 4.7% to 12.0% [Stangier and Feuring, 2012]. These percentages 6

8 meet the acceptance criteria of 15% or less for the validation of bioanalytical methods for phamacokinetic tests [Stangier and Feuring, 2012]. The precision between two assays (between-run precision), evaluated using the CV measurement, fluctuated between 4.0% and 10.0% [Stangier and Feuring, 2012]. As to inter-assay precision (between-day precision), the CV was 8.3% or less [Stangier and Feuring, 2012]. The repeatability (within-run precision), measured by Stangier et al. using the CV, was 2.6%, 3.1%, and 1.2% for dabigatran concentrations of 100, 500, and 1,500 nmol/l respectively [Stangier and Feuring, 2012]. By comparison, Douxfils et al. obtained lower values for the reproducibility (1.0%) as well as for the intra- (0.9%) and inter- (2.5%) assay variability [Douxfils et al., 2012]. Analytical Sensitivity The Hemoclot Thrombin Inhibitors method, used in the low range to measure dabigatran in plasma, has a sensitivity of approximately 20 ng/ml [HYPHEN, 2012a]. Douxfils et al. estimated the sensitivity of this test at 8 ng/ml. Concentration Range The Dabigatran Plasma Calibrator commercial kit allows a calibration curve to be obtained that ranges from < 50 ng/ml to 500 ng/ml [HYPHEN, 2012a]. The resulting calibration curve encompasses the concentrations usually observed during dabigatran treatments. The concentration range tested by Douxfils et al. included values from 53 ng/ml to 941 ng/ml [Douxfils et al., 2012]. The evaluations by Stangier et al. [2012] involved concentrations ranging from 50 nmol/l to 4,000 nmol/l (23.58 ng/ml to 1,886 ng/ml). It is unlikely that plasma concentrations in individuals using dabigatran will exceed 2,000 nmol/l [Stangier and Feuring, 2012]. Interference and Other Limitations Blood activation during specimen collection and plasma preparation may interfere with the assay [HYPHEN, 2010]. The manufacturer recommends discarding any sample presenting an unusual aspect (icteric, hemolyzed, lipemic, etc.). No significant interference (deficiency or excess of the other coagulation factors) was identified, which is in compliance with the principle for a test using diluted test plasma and a substrate plasma in excess. However, special caution is recommended for plasma samples with constitutional or acquired hypocoagulability. To obtain optimal assay performance from the Hemoclot Thrombin Inhibitors kit, the working instructions must be carefully followed. Each laboratory should establish and verify its own working range, expected values and acceptance ranges, in the exact laboratory working conditions (combination of assayed DTI, reagent lots, and instruments used), and for its specific application. Neither Hemoclot Thrombin Inhibitors nor ECA detected dabigatran in 35 patients not treated with dabigatran or treated with another anticoagulant [Antovic et al., 2013]. Moreover, the results of the two tests were not affected by a deficiency in factor VIII, vwf, lupus anticoagulant, therapeutic (INR 2-3) or supratherapeutic (INR 3) warfarin, or by heparin or low-molecular-weight heparin [Antovic et al., 2013]. Matrix Effect The mean coagulation time was 36.2 s (35.6 to 37.0), 63.8 s (62.1 to 65.1) and 110 s (100.9 to 117.3) at dabigatran concentrations of 100, 500 and 1,500 nmol/l, respectively [Stangier and Feuring, 2012]. The CV corresponding to the previous measurements was 1.6% at dabigatran concentrations of 100 nmol/l and 500 nmol/l, and 5.2% at 1,500 nmol/l [Stangier and Feuring, 2012]. 7

9 Bland-Altman Method Overall, the discrepancies reported between assays carried out using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and the Hemoclot Thrombin Inhibitors kit, based on the Bland-Altman method, averaged 9 ng/ml, with a 95% confidence interval ± 20 ng/ml [Douxfils et al., 2013]. These statistics were not as good at a dabigatran concentration of 100 ng/ml (mean difference of - 12 ng/ml [standard deviation of 9 ng/ml] and 95% confidence interval from -29 ng/ml to 4 ng/ml). Correlation Between the Test and the Comparator The calibration curve from the Hemoclot Thrombin Inhibitors kit is valid when the linearity (coefficient of determination: r ) and the concentrations obtained for the controls are within the acceptance range [HYPHEN, 2010]. Using the equation of the regression line 27, the back- calculations of the concentration of the dabigatran samples of 100, 500 and 1,500 nmol/l were, on average, 79.3 nmol/l (95% CI: from 68.1 to 90.5), nmol/l (95% CI: from to 628.0) and 1,583.3 nmol/l (95% CI: from 1,488.6 to 1,678.0) [Stangier and Feuring, 2012]. Consequently, the mean bias, as a percentage (%), was at 100 nmol/l, at 500 nmol/l and at 1,500 nmol/l. LC-MS/MS has been used as a gold standard to validate the results from the Hemoclot Thrombin Inhibitors kit and the ECA test. The correlation between the concentration of dabigatran determined by LC-MS/MS and that determined by the Hemoclot Thrombin Inhibitors kit (r 2 = 0.97) or ECA (r 2 = 0.96) was excellent. The ECA tended to overestimate the concentration of dabigatran. At low concentrations (30 ng/l to 50 ng/l), the ECA performed better than the Hemoclot Thrombin Inhibitors kit. Douxfils et al. obtained the same correlation between the concentration of dabigatran determined by LC-MS/MS and that determined by Hemoclot Thrombin Inhibitors (r 2 = 0.97). Stangier et al. [2011] also evaluated the validity of the HEMOCLOT Thrombin Inhibitors test by using LC- MS/MS as a gold standard. In this study, 100 samples with low or high concentrations of dabigatran were tested. The mean deviation between the measurement by Hemoclot Thrombin Inhibitors and the gold standard was 14% at 122 ng/ml. The deviation decreased to % at 285 ng/ml. Based on these results, the validity of the Hemoclot Thrombin Inhibitors test is acceptable only for high concentrations of dabigatran [Stangier et al., 2011]. 5.4 Recommendations for Listing in Other Jurisdictions In 2012, Douxfils et al. reported that no clinical guidelines had yet been established concerning which method should be used to measure dabigatran [Douxfils et al., 2012]. Nevertheless, in 2011, Australian authorities recommended the use of the ACT test to rule out the risk of bleeding associated with the use of dabigatran [Douxfils et al., 2012; Australian Government, 2011]. 6 POSSIBLE OUTCOMES OF INTRODUCING THE TEST 6.1 Impact on Material and Human Resources: Not assessed. 6.2 Economic Consequences of Introducing the Test Into Quebec's Health Care and Social Services System: Not assessed. 6.3 Main Organizational, Ethical, and Other (Social, Legal, Political) Issues: Not assessed. 27. Concentration of dabigatran (nmol/l) = clotting time in seconds. The value of r 2 in this equation is

10 7 IN BRIEF 7.1 Clinical Relevance The only valid and precise test that is commercially available, easy to calibrate and developed specifically for the quantitative measurement of dabigatran in a clinical setting. 7.2 Clinical Validity: No studies available, to our knowledge. 7.3 Analytical Validity: Very good. 7.4 Recommendations for Listing in Other Jurisdictions No clinical guidelines have determined which method should be used for the measurement of dabigatran. 9

11 8 INESSS NOTICE IN BRIEF Measurement of Direct Anti-IIa Activity of Dabigatran Status of the Diagnostic Technology Established Innovative: The technique is established; its application, in the case of dabigatran, is innovative. Experimental (for research purposes only) Replacement for technology:, which becomes obsolete INESSS Recommendation Add test to the Index The assumption of clinical utility and the relevance of this test are significant; this concerns patients who are hemorrhaging or who are at risk of hemorrhage as a result of an emergency surgery. The production of clinical data will take time. Controlling the serious side effects of dabigatran is of the utmost importance. This is the only valid and precise test that is commercially available, easy to calibrate, and developed specifically for the quantitative measurement of dabigatran in a clinical setting. It is recommended that the test be added to the Index, despite the lack of data on its clinical validity, in view of the seriousness of the problem and the risks associated with the use of the drug. Do not add test to the Index Reassess test Additional Recommendation Draw connection with listing of drugs, if companion test Production of an optimal use guide Introduction is conditional upon the monitoring of the results and the development (or publication) of usage protocols. 10

12 REFERENCES Antovic JP, Skeppholm M, Eintrei J, Boija EE, Soderblom L, Norberg EM, et al. Evaluation of coagulation assays versus LC-MS/MS for determinations of dabigatran concentrations in plasma. Eur J Clin Pharmacol 2013;69(11): Association des pharmaciens du Canada (APhC).Pradaxa MC dabigatran etexilate [electronic resource]. Dans e-cps : Compendium des produits et spécialités pharmaceutiques. Ottawa, ON APhC; Available from: (consulté le 9 septembre 2013). Australian Government. Australian public assessment report for dabigatran etexilate mesilate.woden, Australie Therapeutic goods administration; Available from: (consulté le 31 juillet 2013). Chin PKL, Barclay ML, Begg EJ. Rifampicin and dabigatran etexilate: A place for laboratory coagulation monitoring. Br J Clin Pharmacol 2013;75(2): Douxfils J, Dogne JM, Mullier F, Chatelain B, Ronquist-Nii Y, Malmstrom RE, Hjemdahl P. 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): Douxfils J, Mullier F, Robert S, Chatelain C, Chatelain B, Dogne 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): Fawole A, Daw HA, Crowther MA.Practical management of bleeding due to the anticoagulants dabigatran, rivaroxaban, and apixaban. Cleve Clin J Med 2013;80(7): Garcia D, Barrett YC, Ramacciotti E, Weitz JI. Laboratory assessment of the anticoagulant effects of the next generation of oral anticoagulants. J Thromb Haemost 2013;11(2): Girard-Desbiens C, Nadeau C, Blais N. Can common coagulation assays be used to estimate dabigatran or rivaroxaban concentration? An interlaboratory comparison of 41 hospitals in Quebec.54th Annual Meeting of the American Society of Hematology, ASH. Blood 2012;120(21):abstract 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): Hawes EM, Deal AM, Funk-Adcock D, Gosselin R, Jeanneret C, Cook AM, 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): HYPHEN BioMed.Dabigatran plasma calibrator.ref A Calibration plasmas for the assay of dabigatran with anti-iia method West Chester, OH Aniara; Available from: (consulté le 27 juillet 2013). 11

13 HYPHEN BioMed. Dabigatran control plasma. Ref A Human plasmas at two levels of dabigatran for the quality control of dabigatran measurements with anti-iia method West Chester, OH Aniara; Available from: (consulté le 27 juillet 2012). HYPHEN BioMed.HEMOCLOT thrombin inhibitors ACK002L. Clotting assay for the quantitative measurement of hirudin and other direct thrombin inhibitors in plasma West Chester, OH Aniara; Available from: (consulté le 27 juillet 2013). HYPHEN BioMed. BIOPHEN DTI. Ref. A Quantitative determination of direct thrombin inhibitors (DTI) with a chromogenic method.west Chester, OH Aniara; Available from: (consulté le 27 juillet 2013). Institute for safe medication practices (ISMP). Anticoagulants the leading reported drug risk in Horsham, PA ISMP; Available from: (consulté le 31 juillet 2013). Messier K and Lapierre M. Le dabigatran (Pradax) une question de bon sang!. Le Médecin du Québec 2011;46(7): Miyares MA and Davis K. Newer oral anticoagulants: a review of laboratory monitoring options and reversal agents in the hemorrhagic patient. Am J Health Syst Pharm 2012;69(17): Revue Prescrire.Saignement sous dabigatran, rivaroxaban ou apixaban. La Revue Prescrire 2013;33(353): 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): Stangier J and Clemens A. Pharmacology, pharmacokinetics, and pharmacodynamics of dabigatran etexilate, an oral direct thrombin inhibitor. Clin Appl Thromb Hemost 2009;15(Suppl 1):9S-16S. Stangier J, Eriksson BI, Huo MH, Friedman RJ, Dahl OE, Feuring M. Validation of the HEMOCLOT direct thrombin inhibitor assay for dabigatran by comparison with a validated LC-MS/MS method in plasma samples from patients after major orthopaedic surgery. Conference: 53rd Annual Meeting of the American Society of Hematology, ASH. Blood 2011;118(21):abstract Stangier J and Feuring M. Using the HEMOCLOT direct thrombin inhibitor assay to determine plasma concentrations of dabigatran. Blood Coagul Fibrinolysis 2012;23(2): Tripodi A. The laboratory and the new oral anticoagulants. Clin Chem 2013;59(2): van Ryn J, Stangier J, Haertter S, Liesenfeld KH, Wienen W, Feuring M, Clemens A. Dabigatran etexilate- -a novel, reversible, oral direct thrombin inhibitor: interpretation of coagulation assays and reversal of anticoagulant activity. Thromb Haemost 2010;103(6):