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Job Harenberg - One of the best experts on this subject based on the ideXlab platform.

  • Determination of dabigatran in plasma, serum, and urine samples: comparison of six methods
    Clinical chemistry and laboratory medicine, 2015
    Co-Authors: Christel Weiß, Roland Krämer, Giese Christina, Sandra Krämer, Martin Wehling, Job Harenberg
    Abstract:

    BACKGROUND Assessing the anticoagulant effect of dabigatran may be useful in certain clinical settings. When plasma sampling is not available, serum or urine samples may provide another option for dabigatran determinations. METHODS Dabigatran was assessed in patients on treatment under real-life conditions in plasma samples by four Clotting Time-based assays and in plasma, serum, and urine samples by two chromogenic substrate methods. RESULTS The concentrations of dabigatran in patients' plasma samples were not different for the Hemoclot test (106.8±89.4 ng/mL) and the Ecarin Clotting Time (ECT, 109.5±74.5 ng/mL, p=0.58). Activated partial thromboplastin Time and prothrombinase-induced Clotting Time showed low correlations with the other assays. Chromogenic assays measured similar concentrations as Hemoclot and ECT. For both chromogenic assays, the concentrations of dabigatran were about 70% lower in serum than in plasma samples (p

  • Determination of the anticoagulant effects of new oral anticoagulants: an unmet need
    Expert review of hematology, 2012
    Co-Authors: Job Harenberg, Svetlana Marx, Sandra Erdle, Roland Krämer
    Abstract:

    Thromboembolic diseases require anticoagulation for their prevention and treatment. New oral anticoagulants, specifically direct factor Xa and thrombin inhibitors, were developed to overcome the limitations of conventional anticoagulants. Their benefit has been demonstrated using fixed doses without laboratory-guided dose adjustment for patients following elective knee and hip replacement, treatment of venous thromboembolism and prevention of embolic events in atrial fibrillation. These anticoagulants are excreted by glomerular filtration at a rate of between 25 and 80%. Thus, lower doses are required for patients with impaired renal function. Therefore, determination of the anticoagulant effects may be needed in other specific patient populations. Prothrombin Time, activated partial thromboplastin Time, prothrombin-induced Clotting Time, Ecarin Clotting Time, hemoclot assay, other specific coagulation assays and chromogenic substrate are available to determine the effect of the anticoagulants. Standardiz...

  • Determination of antithrombin-dependent factor Xa inhibitors by prothrombin-induced Clotting Time.
    Seminars in Thrombosis and Hemostasis, 2007
    Co-Authors: Job Harenberg, Antje Hagedorn, Christina Giese, Inge Traeger, Tivadar Fenyvesi
    Abstract:

    Prothrombinase-induced Clotting Time (PiCT) determines the anticoagulant effects of heparins, low molecular weight heparins (LMWHs), and direct thrombin inhibitors. At present, this is the only method that measures the effects of all of these inhibitors, in contrast to the prothrombin Time, activated partial thromboplastin Time (aPTT), Heptest, Ecarin Clotting Time, and the chromogenic assays. The antithrombin-dependent direct factor (F) Xa inhibitors fondaparinux and idraparinux were compared with the LMWH dalteparin on PiCT, aPTT, Heptest, and chromogenic anti-FXa assays in pooled human normal plasma samples. Fondaparinux and idraparinux prolonged the coagulation Times in the PiCT, Heptest, and chromogenic FXa assays in a dose-dependent manner, in contrast to the aPTT. We conclude that PiCT is a suitable assay to determine the anticoagulant effects of these two new FXa inhibitors in patients receiving treatment with these compounds.

  • comparison of two different Ecarin Clotting Time methods
    Journal of Thrombosis and Thrombolysis, 2005
    Co-Authors: Tivadar Fenyvesi, Job Harenberg, Christel Weiß, Ingrid Jorg
    Abstract:

    Background: Ecarin Clotting Time (ECT) assay specifically determines the inhibition of meizothrombin by direct thrombin inhibitors (DTI). Blood coagulation factor levels lowered by vitamin K antagonists (VKA) may prolong ECT. Concomitant treatment of VKA with DTI may influence differently the two published ECT methods.

  • Collaborative Study On Monitoring Methods To Determine Direct Thrombin Inhibitors Lepirudin And Argatroban On behalf of the Control of Anticoagulation Subcommittee of the Scientific and Standardization Committee of the International Society of Thromb
    2005
    Co-Authors: E. Gray, Job Harenberg
    Abstract:

    SUMMARY Background: Direct thrombin inhibitors are now used clinically for the prophylaxis and treatment of thrombosis and related cardiovascular diseases. Although all these inhibitors bind to thrombin, their modes of action are different. Routine anticoagulant monitoring tests such as the APTT are used to estimate the activity of these inhibitors. However, no studies have been carried out to assess the suitability of these tests. Methods: An international collaborative study was carried out utilising a panel of plasmas spiked with lepirudin and argatroban to evaluate the robustness and the sensitivity of the different monitoring methods. Results: Thirteen laboratories took part in the trial. The point-of-care TAS-analyser, using cards with high or low concentrations of Ecarin reagents gave the lowest intra- and inter- laboratory variation. APTT using local or common APTT reagents also showed acceptable within and between-laboratory variations. The chromogenic anti-IIa activity and the wet Ecarin Clotting Time gave higher inter-laboratory variations. The ELISA for lepirudin had the highest inter-laboratory variation. Conclusion: APTT and the TAS-analyser with ECT-cards gave the most reproducible results compared to other methods. Further studies will evaluate the validity for patient samples.

Tivadar Fenyvesi - One of the best experts on this subject based on the ideXlab platform.

  • Determination of antithrombin-dependent factor Xa inhibitors by prothrombin-induced Clotting Time.
    Seminars in Thrombosis and Hemostasis, 2007
    Co-Authors: Job Harenberg, Antje Hagedorn, Christina Giese, Inge Traeger, Tivadar Fenyvesi
    Abstract:

    Prothrombinase-induced Clotting Time (PiCT) determines the anticoagulant effects of heparins, low molecular weight heparins (LMWHs), and direct thrombin inhibitors. At present, this is the only method that measures the effects of all of these inhibitors, in contrast to the prothrombin Time, activated partial thromboplastin Time (aPTT), Heptest, Ecarin Clotting Time, and the chromogenic assays. The antithrombin-dependent direct factor (F) Xa inhibitors fondaparinux and idraparinux were compared with the LMWH dalteparin on PiCT, aPTT, Heptest, and chromogenic anti-FXa assays in pooled human normal plasma samples. Fondaparinux and idraparinux prolonged the coagulation Times in the PiCT, Heptest, and chromogenic FXa assays in a dose-dependent manner, in contrast to the aPTT. We conclude that PiCT is a suitable assay to determine the anticoagulant effects of these two new FXa inhibitors in patients receiving treatment with these compounds.

  • comparison of two different Ecarin Clotting Time methods
    Journal of Thrombosis and Thrombolysis, 2005
    Co-Authors: Tivadar Fenyvesi, Job Harenberg, Christel Weiß, Ingrid Jorg
    Abstract:

    Background: Ecarin Clotting Time (ECT) assay specifically determines the inhibition of meizothrombin by direct thrombin inhibitors (DTI). Blood coagulation factor levels lowered by vitamin K antagonists (VKA) may prolong ECT. Concomitant treatment of VKA with DTI may influence differently the two published ECT methods.

  • Effects of lepirudin, argatroban and melagatran and additional influence of phenprocoumon on Ecarin Clotting Time
    Thrombosis Research, 2003
    Co-Authors: Tivadar Fenyvesi, Ingrid Jorg, Christel Weiß, Job Harenberg
    Abstract:

    Introduction: Direct thrombin inhibitors (DTI) prolong the Ecarin Clotting Time (ECT). Oral anticoagulants (OA) decrease prothrombin levels and thus interact with actions of DTIs on the ECT method during concomitant therapy. Materials and methods: Actions of lepirudin, argatroban and melagatran on ECT were investigated in normal plasma (NP) and in plasma of patients (n=23 each) on stable therapy with phenprocoumon (OACP). Individual line characteristics were tested statistically. Results: Control ECT in OACP was prolonged compared to NP (50.1F0.9 vs. 45.7F0.8 s; p

  • effects of lepirudin argatroban and melagatran and additional influence of phenprocoumon on Ecarin Clotting Time
    Thrombosis Research, 2003
    Co-Authors: Tivadar Fenyvesi, Ingrid Jorg, Christel Weiß, Job Harenberg
    Abstract:

    Introduction: Direct thrombin inhibitors (DTI) prolong the Ecarin Clotting Time (ECT). Oral anticoagulants (OA) decrease prothrombin levels and thus interact with actions of DTIs on the ECT method during concomitant therapy. Materials and methods: Actions of lepirudin, argatroban and melagatran on ECT were investigated in normal plasma (NP) and in plasma of patients (n=23 each) on stable therapy with phenprocoumon (OACP). Individual line characteristics were tested statistically. Results: Control ECT in OACP was prolonged compared to NP (50.1F0.9 vs. 45.7F0.8 s; p<0.001). Lepirudin prolonged the ECT linearly. Argatroban and melagatran delivered biphasic dose– response curves. OA showed additive effects on the ECT of lepirudin but not of argatroban and melagatran. Both in NP and OACP, the first and second slopes of melagatran were steeper compared to argatroban (primary analysis; p<0.001). When using the same drug, slopes in OACP were steeper than in NP (secondary analysis; p<0.001). At similar molar concentrations, the crossing points of both slopes were significantly higher with melagatran (323.1F11.0 s in NP and 333.2F8.2 s in OACP) than with argatroban (219.6F14.7 and 248.4F15.2 s) corresponding to ratios of 7.1F0.2 and 6.7F0.2 (melagatran) vs. 4.8F0.3 and 4.9F03 with argatroban (p<0.0001). Discussion: The patterns of interactions between vitamin K antagonists and DTI effects are different for bivalent (increase of slope without affecting linearity) and monovalent inhibitors (slight increase or alteration of nonlinear slopes), but there are also differences between the two monovalent inhibitors on thrombin inhibition as determined by ECT. D 2003 Elsevier Ltd. All rights reserved.

  • Effects of lepirudin, argatroban and melagatran and additional influence of phenprocoumon on Ecarin Clotting Time.
    Thrombosis research, 2003
    Co-Authors: Tivadar Fenyvesi, Ingrid Jorg, Christel Weiß, Job Harenberg
    Abstract:

    Direct thrombin inhibitors (DTI) prolong the Ecarin Clotting Time (ECT). Oral anticoagulants (OA) decrease prothrombin levels and thus interact with actions of DTIs on the ECT method during concomitant therapy. Actions of lepirudin, argatroban and melagatran on ECT were investigated in normal plasma (NP) and in plasma of patients (n=23 each) on stable therapy with phenprocoumon (OACP). Individual line characteristics were tested statistically. Control ECT in OACP was prolonged compared to NP (50.1+/-0.9 vs. 45.7+/-0.8 s; p<0.001). Lepirudin prolonged the ECT linearly. Argatroban and melagatran delivered biphasic dose-response curves. OA showed additive effects on the ECT of lepirudin but not of argatroban and melagatran. Both in NP and OACP, the first and second slopes of melagatran were steeper compared to argatroban (primary analysis; p<0.001). When using the same drug, slopes in OACP were steeper than in NP (secondary analysis; p<0.001). At similar molar concentrations, the crossing points of both slopes were significantly higher with melagatran (323.1+/-11.0 s in NP and 333.2+/-8.2 s in OACP) than with argatroban (219.6+/-14.7 and 248.4+/-15.2 s) corresponding to ratios of 7.1+/-0.2 and 6.7+/-0.2 (melagatran) vs. 4.8+/-0.3 and 4.9+/-03 with argatroban (p<0.0001). The patterns of interactions between vitamin K antagonists and DTI effects are different for bivalent (increase of slope without affecting linearity) and monovalent inhibitors (slight increase or alteration of nonlinear slopes), but there are also differences between the two monovalent inhibitors on thrombin inhibition as determined by ECT.

Fritz Mertzlufft - One of the best experts on this subject based on the ideXlab platform.

  • a quick assay for monitoring recombinant hirudin during cardiopulmonary bypass in patients with heparin induced thrombocytopenia type iiadaptation of the Ecarin Clotting Time to the act ii device
    The Journal of Thoracic and Cardiovascular Surgery, 2000
    Co-Authors: Reas Koster, Roland Hansen, Mathias Bauer, Fritz Mertzlufft, Matthias Loebe
    Abstract:

    Abstract Background: Recombinant hirudin is increasingly advocated as a promising alternative anticoagulation for patients with heparin-induced thrombocytopenia type II during cardiopulmonary bypass. This requires monitoring of the Ecarin Clotting Time. No commercial Ecarin Clotting Time assay is available for clinical use. We adapted the Ecarin Clotting Time to the easy-to-handle ACT II device. Methods: Three different concentrations of the Ecarin reagent (20, 10, 5 U/mL) were investigated as preliminary studies. Standard calibration curves were constructed for concentrations of recombinant hirudin ranging from 0 to 5 μg/mL. In vivo samples were collected from patients with heparin-induced thrombocytopenia type II who underwent cardiopulmonary bypass, and the values were compared with the values obtained by the chromogenic method. The final concentration for the assay of 5 IU/mL Ecarin was further assessed in vitro for reproducibility and the influence of variations in hematocrit, platelet count, and procoagulants. Results: All three concentrations of Ecarin revealed linearity to 5 μg/mL concentrations of recombinant hirudin. The Ecarin concentration of 5 U/mL revealed the best correlation (0.87) to the laboratory method, was reproducible over the whole recombinant hirudin range, and was not influenced by the variations in the in vitro setup. Conclusions: The ACT II/Ecarin Clotting Time with an Ecarin concentration of 5 U/mL is a simple and reliable assay for monitoring recombinant hirudin during cardiopulmonary bypass. Use of this assay allows a wider use of recombinant hirudin in patients with heparin-induced thrombocytopenia type II during bypass and thereby may contribute to the safer management of these patients. (J Thorac Cardiovasc Surg 2000;119:1278-83)

  • hirudin monitoring using the tas Ecarin Clotting Time in patients with heparin induced thrombocytopenia type ii
    Journal of Cardiothoracic and Vascular Anesthesia, 2000
    Co-Authors: Andreas Koster, Roland Hansen, Mathias Bauer, O Grauhan, Harald Hausmann, Herrmann Kuppe, Roland Hetzer, Fritz Mertzlufft
    Abstract:

    Abstract Objective: To assess the reliability of the TAS/Ecarin Clotting Time (ECT) for on-line monitoring of r-hirudin in cardiovascular surgery with and without cardiopulmonary bypass (CPB). Design: Samples were spiked with r-hirudin (0 to 5 μg/mL) and calibration curves constructed. Reproducibility was evaluated by measurement of the sample five Times at each concentration. The influence of variations in hematocrit, plasma factors, and platelet count on the test results was examined. Samples were obtained from patients during cardiovascular surgery with CPB (n = 8), without CPB (n = 3), and from volunteers (n = 5) and compared with the laboratory reference tests. All tests were performed in duplicate. Setting: Deutsches Herzzentrum Berlin. Participants: Five healthy volunteers and 11 patients undergoing cardiovascular surgery. Interventions: None. Measurements and Main Results: The TAS/ECT showed linearity and reliability to an r-hirudin concentration of 5 μg/mL and was not influenced (p

  • hirudin monitoring using the tas Ecarin Clotting Time in patients with heparin induced thrombocytopenia type ii
    Journal of Cardiothoracic and Vascular Anesthesia, 2000
    Co-Authors: Andreas Koster, Roland Hansen, Mathias Bauer, O Grauhan, Harald Hausmann, Herrmann Kuppe, Roland Hetzer, Fritz Mertzlufft
    Abstract:

    Objective: To assess the reliability of the TAS/Ecarin Clotting Time (ECT) for on-line monitoring of r-hirudin in cardiovascular surgery with and without cardiopulmonary bypass (CPB). Design: Samples were spiked with r-hirudin (0 to 5 μg/mL) and calibration curves constructed. Reproducibility was evaluated by measurement of the sample five Times at each concentration. The influence of variations in hematocrit, plasma factors, and platelet count on the test results was examined. Samples were obtained from patients during cardiovascular surgery with CPB (n = 8), without CPB (n = 3), and from volunteers (n = 5) and compared with the laboratory reference tests. All tests were performed in duplicate. Setting: Deutsches Herzzentrum Berlin. Participants: Five healthy volunteers and 11 patients undergoing cardiovascular surgery. Interventions: None. Measurements and Main Results: The TAS/ECT showed linearity and reliability to an r-hirudin concentration of 5 μg/mL and was not influenced (p <0.005) by the varying conditions of the in vitro setup. The correlation to the laboratory method was 0.74 for the CPB group and 0.87 for the non-CPB group. Conclusions: The TAS/ECT is a reliable assay for monitoring r-hirudin at the point of care. With this information, the use of r-hirudin during surgery or angioplasty should become more effective and safer. Copyright © 2000 by W.B. Saunders Company

Götz Nowak - One of the best experts on this subject based on the ideXlab platform.

  • Monitoring von direkten Thrombininhibitoren
    Hämostaseologie, 2010
    Co-Authors: Götz Nowak
    Abstract:

    Direkte Thrombininhibitoren (DTI) haben meist nur eine geringe therapeutische Breite. Zur Vermeidung von Blutungskomplikationen wird ein Drug-Monitoring empfohlen. Besonders gut geeignet sind Meizothrombingenerierungstests wie die ECT (“Ecarin Clotting Time„) und der ECA (“Ecarin chromogenic assay„). Im klinischen Alltag wird die Therapieuberwachung mit der aktivierten partiellen Thromboplastinzeit (APTT) durchgefuhrt.

  • drug monitoring of argatroban using the Ecarin chromogenic assay
    Seminars in Thrombosis and Hemostasis, 2008
    Co-Authors: Götz Nowak, Ute Lange, Elke Bucha
    Abstract:

    The Ecarin chromogenic assay (HaemoSys ECA; JenAffin GmbH, Jena, Germany) was developed for quantitative determination of direct thrombin inhibitors. As a further development of the Ecarin Clotting Time (ECT), the ECA is based on the same principle of measurement: the activation of prothrombin by Ecarin, a snake venom from Echis carinatus. In the ECA, the prothrombin activation products meizothrombin and meizothrombin-des-F1 cleave a chromogenic substrate. The activity of meizothrombin/ meizothrombin-des-F1 is inhibited in a concentration-dependent manner by direct thrombin inhibitors. The ECA-T is an assay for quantitative determination of active site directed synthetic thrombin inhibitors. For argatroban ECA-T, there is a very precise and sensitive method of quantitative drug monitoring. Only very low interindividual variations were found compared with activated partial thromboplastin Time and even ECT. ECA-T is independent of variations in prothrombin levels of the plasma samples. Heparin does not influence the measuring result. ECA-T is performed on manual coagulation analyzers with an option for optical measurement but can also be applied to automated laboratory systems. By the use of ECA-T as a drug-monitoring method, the drug safety of argatroban, most of all in critically ill patients, can be increased.

  • the use of peg hirudin in chronic hemo dialysis monitored by the Ecarin Clotting Time influence on Clotting of the extracorporeal system and hemostatic parameters
    Clinical Nephrology, 2006
    Co-Authors: K Ulbricht, Elke Bucha, Katrin Annett Poschel, G Stein, G Wolf, Götz Nowak
    Abstract:

    Aim: The aim of our study was to investigate the use of polyethylene glycol (PEG)-Hirudin (PEG-H) as an anticoagulant in hemodialysis including drug monitoring with the Ecarin Clotting Time (ECT) in whole blood and to compare this regimen with standard anticoagulant unfractionated heparin (UFH) for influence on hemostatic parameters and clot frequency of the extracorporeal system. Patients and methods: The application of PEG-H as an anticoagulant in patients on chronic HD was studied in 20 patients (12 males, 8 females) from a single center in an exploratory, open-label, controlled, single-blind, dose-finding study. The patients were divided in 2 groups with 10 patients each (Group I and II); both received 3 dialyses with UFH, thereafter Group I received 5 dialyses with PEG-H and Group II 10 dialyses with PEG-H. Starting dose of PEG-H in the first dialysis was a bolus of 0.08 mg/kg bwt, the mean dose of the following HD was 0.041 mg/kg bwt (range 0.026 - 0.065 mg/kg bwt). PEG-H was applied as an intravenous bolus-dose followed by a 0.9% saline as a placebo-infusion. HD was performed regularly 3 Times a week. All dialysis treatments were performed exclusively with a hollow fiber dialyzer type. Fibrinogen, antithrombin III, prothrombin fragments, thrombin-antithrombin and soluble fibrin were measured with commercial tests. ECT was determined in a mechanical coagulometer. A semiquantitative score was given for the presence of clots in the extracorporeal system after each dialysis. Results: PEG-H was effectively used as an anticoagulant in 150 chronic dialysis treatments using ECT as a simple monitoring method. The optimal whole blood concentration for PEG-H is 600 - 1000 ng/ml. Clotting in the whole extracorporeal system was decreased by 45% (p = 0.059) with PEG-H anticoagulated HD in comparison to UFH. Fibrinogen, prothrombin fragments (F1+2-fragments) and thrombin-antithrombin-complex showed no significant change in comparison with UFH, antithrombin III (AT III) increased to normal concentrations. Highly sensitive coagulation markers such as a soluble fibrin showed a significant decrease (p < 0.001) before and after HD with PEG-H compared with UFH. Conclusion: PEG-H can be used effectively as an alternative anticoagulant in patients on chronic HD using ECT as a simple drug monitoring method. The lower frequency of clots in the extracorporeal system, the stronger and more efficient inhibition of coagulation during HD as indicated by soluble fibrin, may have a positive influence on the disturbed blood coagulation of these patients.

  • Ecarin chromogenic assay: an innovative test for quantitative determination of direct thrombin inhibitors in plasma
    Hamostaseologie, 2005
    Co-Authors: Ute Lange, Götz Nowak, Andrea Olschewski, Elke Bucha
    Abstract:

    The Ecarin chromogenic assay (ECA) was developed for quantitative determination of direct thrombin inhibitors. As a further development of the Ecarin Clotting Time (ECT), the ECA is based on the same principle, the activation of prothrombin by Ecarin a snake venom from Echis carinatus. In the ECA the prothrombin activation products meizothrombin and meizothrombin-desF1 cleave a chromogenic substrate, whereas in the Clotting assay ECT plasma fibrinogen is converted to fibrin. The activity of meizothrombin/meizothrombin-desF1 is inhibited in a concentration-dependent fashion by direct thrombin inhibitors. The ECA can be used as ECA-H for quantitative determination of hirudin and as ECA-T for determination of synthetic thrombin inhibitors. As shown for hirudin, argatroban and melagatran, the ECA turned out as a very precise and sensitive method, which combines the advantages of ECT with those of chromogenic assays. In ECA very low interindividual variations were found compared to aPTT and even ECT. The ECA is independent of the variations of the coagulation variables prothrombin and fibrinogen.

  • Characterization of the postglomerular renal metabolism of lepirudin in healthy volunteers
    Thrombosis Research, 2004
    Co-Authors: Michael Kautzleben, Sperschneider H, Günter Stein, Götz Nowak
    Abstract:

    Abstract Introduction : The anticoagulant r-hirudin lepirudin is eliminated exclusively via the kidneys. We examined the C-terminal amino acid degradation of lepirudin by the proximal kidney tubulus cells in humans as well as the antithrombotic efficacy of the metabolites and quantified the metabolite portions. Materials and methods : In vitro metabolites of lepirudin were produced by adding 250 μg lepirudin to urine of three healthy volunteers and a concentration of 100 ml fresh urine to 1.5 ml and subsequent separation by high performance liquid chromatography. Anticoagulant activities of the mass spectrometrically identified metabolites were measured by Ecarin Clotting Time and protein determination with bicinchoninic acid. In 10 healthy volunteers 1 mg lepirudin was administered intravenously, urine was collected during the following 2 h. The urine amount containing 50 μg lepirudin measured by Ecarin Clotting Time was enzyme-inactivated and measured analogously to the in vitro samples. Results : The in vitro generated metabolites were shortened amino acid by amino acid at the C-terminal end, up to five amino acids. Their anticoagulant activity was reduced to 92.6% (M 64 ), 80.1% (M 63 ) and 74.4% (M 60,61,62 ) in comparison to lepirudin. Lepirudin (57.9±8.6%) was eliminated unchanged via the kidneys. Identical to the in vitro situation metabolite fragments were built in the distribution M 64 =8.1±5.7%, M 63 =21.1±6.5%, and M 60,61,62 =12.9±4.5%. Conclusions : Lepirudin is metabolized spontaneously in more than 10-fold concentrated urine. Metabolization of lepirudin takes place in the proximal tubulus cells as well. In vitro, the degradation takes place amino acid by amino acid, but in vivo even dipeptides and perhaps tripeptides are degraded.

Robert C. Gosselin - One of the best experts on this subject based on the ideXlab platform.

  • Comparing Direct Thrombin Inhibitors Using aPTT, Ecarin Clotting Times, and Thrombin Inhibitor Management Testing
    2016
    Co-Authors: Robert C. Gosselin, William E Dager, Kim A Janatpour, Jeffrey H. King, Edward C. Larkin, John T. Owings
    Abstract:

    Patients with documented heparin-induced thrombocy-topenia and thrombosis (HITT) or high suspicion for HITT, may be acutely anticoagulated with direct thrombin inhibitors (DTIs) until long-term anticoagulation with war-farin is achieved. The most common means of monitoring DTI treatment is using the activated partial thromboplastin Time (aPTT), with a target aPTT ratio from 1.5 to 2.5 or 3.0.1,2 However, the aPTT is of limited use in patients with HITT requiring higher DTI dosing in cardiopulmonary by-pass or cardiac intervention procedures. Other methods that have been employed for monitoring the anticoagulant effects of DTIs have included the Ecarin Clotting Time (ECT) and the activated Clotting Time.3,4 The ECT method is based on the principle that the snake venom Ecarin cleaves prothrombin to form meizothrombin, which will, in turn, cleave fibrinogen to form fibrin. In the ECT method, the DTIs present in plasma will bind meizothrombin, there-by prolonging clot formation. A newer method, the throm-bin inhibitor management (TIM), not yet approved for clinical use, is based on a modified Ecarin Clotting Time.4 In this study, we sought to compare aPTTs and aPTT ra-tios obtained from samples containing 0.1–1.2 µg/mL of one of the following DTIs: argatroban, bivalirudin, or lep-irudin. We also compared the ECT and TIM methods from plasma containing 0.1–8.0 µg/mL of these DTIs

  • Performance of Various Laboratory Assays in the Measurement of Dabigatran in Patients Receiving Therapeutic Doses
    American Journal of Clinical Pathology, 2014
    Co-Authors: Robert C. Gosselin, Emily M. Hawes, Stephan Moll, Dorothy M. Adcock
    Abstract:

    Objectives: To study dabigatran etexilate, a new oral anticoagulant that functions as a direct thrombin inhibitor. Methods: This study evaluates four methods, one of which is performed in three different laboratories, and compares results against dabigatran levels measured by Boehringer-Ingelheim (Ingelheim, Germany) using mass spectrometry. Results: Although routine monitoring is not required, measurement of plasma concentrations may be necessary in certain clinical situations. Routine coagulation assays such as the prothrombin Time, activated partial thromboplastin Time, and thrombin Time do not reliably determine levels of dabigatran anticoagulation. Alternative assays, when calibrated with a dabigatran standard, such as the modified dilute thrombin Time, Ecarin Clotting Time, and Ecarin chromogenic assay, may be appropriate, although a comparison of these methods using samples from patients taking dabigatran has not been performed. Conclusions: Although results using all methods in this study demonstrate adequate correlation, measured dabigatran levels varied in a statistically significant manner, even when the same method was used by different laboratories. The clinical significance of this variation in dabigatran concentrations is uncertain.

  • measuring dabigatran concentrations using a chromogenic Ecarin Clotting Time assay
    Annals of Pharmacotherapy, 2013
    Co-Authors: Robert C. Gosselin, Denis M. Dwyre, William E Dager
    Abstract:

    Background: Clinicians managing patients receiving the direct thrombin inhibitor dabigatran may benefit in being able to determine the amount of drug present in selected situations. This may include assessment of accumulation, concurrent drug interactions, or adequate removal from circulation. The ability to estimate the amount of dabigatran present using the chromogenic Ecarin assay (ECA) requires further clarification. Objective: To describe the reliability of dabigatran measurements using a chromogenic ECA. Methods: This was an evaluation of the ECA method that incorporated assessment of imprecision, linearity, accuracy, carryover, and lower limits of detection or blank. Pooled normal plasma enriched with dabigatran at concentrations of 0, 25, 50, 75, 100, 125, 150, 200, 300, 400, and 500 ng/mL were sent blinded to 3 laboratories in the United States to compare our ECA results with those of laboratories reporting dilute thrombin Time methods (HEMOCLOT thrombin inhibitor assay) for measuring dabigatran....

  • comparing direct thrombin inhibitors using aptt Ecarin Clotting Times and thrombin inhibitor management testing
    Annals of Pharmacotherapy, 2004
    Co-Authors: Robert C. Gosselin, William E Dager, Kim A Janatpour, Jeffrey H. King, Edward C. Larkin, John T. Owings
    Abstract:

    BACKGROUND:Patients with heparin-induced thrombocytopenia and thrombosis may be acutely anticoagulated with direct thrombin inhibitors (DTIs). The anticoagulation is typically monitored using the activated partial thromboplastin Time (aPTT) or Ecarin Clotting Time (ECT).OBJECTIVE:To compare 14 methods for measuring aPTT, as well as ECT and thrombin inhibitor management test (TIM), in samples containing DTIs.METHODS:DTIs were added to pooled normal plasma to achieve low (0.1–1.2 μg/mL) and high (1.5–8.0 μg/mL) drug concentrations. Each low-concentration DTI sample was tested using all aPTT reagents, while each low- and high-concentration DTI was tested using the ECT and TIM.RESULTS:All aPTT reagents had a significant dose-dependent correlation with drug concentration. Only Actin FSL and APTT-S demonstrated equivalent aPTT ratios obtained from any DTI. The TAS-aPTT was the most sensitive aPTT reagent to argatroban, with the aPTT ranging from 52.7 to 121.2 seconds corresponding to 0.1 to 1.2 μg/mL of drug co...