Performance of coagulation tests in patients on therapeutic doses of dabigatran: a cross-sectional pharmacodynamic study based on peak and trough plasma levels

Hemostasis Testing in the Emergency Department: A Narrative Review

Routine laboratory screening is typically performed at initial evaluation of the vast majority of presentations to the emergency department (ED). These laboratory results are crucial to the diagnostic process, as they may influence up to 70% of clinical decisions. However, despite the usefulness of biological assessments, many tests performed are inappropriate or of doubtful clinical relevance. This overutilization rate of laboratory testing in hospitals, which represents a significant medical-economic burden, ranges from 20 to 67%, with coagulation tests at the top of the list. While reviews frequently focus on nonintensive care units, there are few published assessments of emergency-specific interventions or guidelines/guidance to date. The aim of this review is to highlight current recommendations for hemostasis evaluation in the emergency setting with a specific analysis of common situations leading to ED admissions, such as suspected venous thrombosis or severe bleeding. We revisit the evidence related to the assessment of patient's hemostatic capacity based on comprehensive history taking and physical examination as well as best practice recommendations for blood sample collection to ensure the reliability of results. This review also includes an examination of various currently available point of care tests and a comprehensive discussion on indications, limitations, and interpretation of these tests.

International Council for Standardization in Haematology recommendations for laboratory measurement of factor VIII and FIX type I inhibitors

This guidance document has been prepared on behalf of the International Council for Standardisation in Hematology. The aim of the document is to provide guidance and recommendations on the measurement of factor VIII (FVIII) and factor IX (FIX) inhibitors. After an introduction on the clinical background and relevance of factor VIII and factor IX inhibitor testing, the following aspects of laboratory testing are included: screening for inhibitors, assay principle, sample requirements, testing requirements and interpretation, quality assurance, interferences and recent developments. This guidance document focusses on recommendations for a standardised procedure for the laboratory measurement of FVIII and FIX type I inhibitors. The recommendations are based on published data in peer-reviewed literature and expert opinion.

Ecarin-Based Methods for Measuring Thrombin Inhibitors

Ecarin is a venom from the saw-scaled viper, Echis carinatus, which catalyzes prothrombin into meizothrombin. This venom is used in several hemostasis laboratory assays, including ecarin clotting time (ECT) and ecarin chromogenic assays (ECA). The use of these ecarin-based assays was first implemented as a tool for monitoring the infusion of a direct thrombin inhibitor, hirudin. Subsequently, this method has been more recently employed for measuring either the pharmacodynamic or pharmacokinetic properties of the oral direct thrombin inhibitor, dabigatran. In this chapter, the procedure for performing manual ECT and automated and manual ECA for measuring thrombin inhibitors is described.

Lupus Anticoagulant Testing: Dilute Prothrombin Time (dPT)

Lupus anticoagulants (LA) rarely affect routine prothrombin time assays because the high phospholipid (PL) content in thromboplastin reagents tends to overwhelm the antibodies. Dilution of thromboplastin to create a dilute prothrombin time (dPT) screening test renders the assay sensitive to the presence of LA. Technical and diagnostic performances are enhanced if recombinant thromboplastins are employed in place of tissue-derived reagents. Presence of an LA cannot be deduced from an elevated screening test alone since other coagulation disturbances can prolong clotting times. Confirmatory testing with less dilute or undiluted thromboplastin reveals the PL-dependent nature of LA by reducing the clotting time relative to that of the screening test. Where appropriate, such as a known or suspected coagulation factor deficiency, mixing tests are valuable in correcting factor deficiencies and evidencing inhibitory properties of LA, to increase diagnostic specificity. Although LA testing is commonly restricted to dilute Russell's viper venom time and activated partial thromboplastin time, dPT is sensitive to LA unreactive in those assays, and inclusion in routine testing increases detection rates of clinically significant antibodies.

Hemoclot Thrombin Inhibitor Assay and Expected Peak-Trough Levels of Dabigatran: A Multicenter Study

Purpose

Dabigatran concentrations monitoring are gaining importance of special situations, but limited data are available for the expected peak and trough levels. The hemoclot thrombin inhibitor (HTI) is dabigatran-calibrated quantitative determination of dabigatran concentration. This study aims to validate HTI assay as the quantification choice of dabigatran, and providing the expected peak and trough levels.

Materials and Methods

This is a multi-center methodology validate study, including seven hospitals from Beijing, Shanghai, Henan, Hunan, Chongqing, and Fujian. We retrospectively analyzed plasma samples taken from 118 healthy subjects and 183 patients receiving dabigatran. Dabigatran concentrations were measured with HTI assay and high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Linear regression, Spearman correlation and Bland-Altman analysis were used in this study.

Results

The mean concentration ratio of HPLC-MS/MS and HTI assays was 1.03 and 0.98 at 2 and 12 h, and the acceptance ranges for both the ratio limit as well as the limit of agreement were met, suggesting good agreement between the HTI-derived plasma concentrations and HPLC-MS/MS. The reference detection range of single dose dabigatran 150 mg in healthy subjects was 33–159 ng/ml. About 500 blood samples were taken from 183 patients suggested that the expected peak and trough levels range of dabigatran 110 mg was about 95–196 and 36–92 ng/ml.

Conclusion

Hemoclot thrombin inhibitor assay can be a good quantitative detection method of dabigatran. Expected peak and trough levels provide a basis for the rational use of dabigatran, and provide important Asian population data for the update of the international clinical guidelines for hematological testing.

Clinical Trial Registration

[https://clinicaltrials.gov], identifier [NCT03161496].

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

Background

Applying a single anti-Xa assay, calibrated to unfractionated heparin to measure rivaroxaban, apixaban, and edoxaban would simplify laboratory procedures and save healthcare costs.

Aim

We hypothesized that a heparin-calibrated anti-Xa assay would accurately measure rivaroxaban, apixaban, and edoxaban drug concentrations and correctly predict clinically relevant drug levels.

Methods

This analysis is part of the Simple-Xa study, a prospective multicenter cross-sectional study conducted in clinical practice. Patients treated with rivaroxaban, apixaban, or edoxaban were included. Anti-Xa activity was measured using the Siemens INNOVANCE^® Heparin assay. Drug concentrations were determined using ultra-high performance liquid chromatography-tandem mass spectrometry (LC-MS/MS). Cut-off levels were determined in a derivation dataset (50% of patients) and sensitivities and specificities were calculated in a verification dataset (50% of patients).

Results

Overall, 845 patients were available for analysis. Correlation coefficients (r _s ) between the heparin-calibrated anti-Xa assay and drug concentrations were 0.97 (95% CI 0.97, 0.98) for rivaroxaban, 0.96 (0.96, 0.97) for apixaban, and 0.96 (0.94, 0.99) for edoxaban. The area under the receiver operating characteristics curve (ROC) was 0.99 for all clinically relevant drug concentrations. In the verification dataset, the sensitivity was 94.2% (95% CI 90.8-96.6) for 30 μg L^-1, 95.8% (92.4-98.0) for 50 μg L^-1, and 98.7% (95.5-99.9) for 100 μg L^-1. Specificities were 86.3% (79.2-91.7), 89.8% (84.5-93.7), and 88.7% (84.2-92.2), respectively.

Conclusion

In a large prospective study in clinical practice, a strong correlation of heparin-calibrated anti-Xa measurements with LC-MS/MS results was observed and clinically relevant drug concentrations were predicted correctly.

Protein-Induced Fluorescence Enhancement and Quenching in a Homogeneous DNA-Based Assay for Rapid Detection of Small-Molecule Drugs in Human Plasma

Homogeneous assays for determining the concentration of small molecules in biological fluids are of importance for monitoring blood levels of critical drugs in patients. We have developed a strand displacement competition assay for the drugs dabigatran, methotrexate, and linezolid, which allows detection and determination of the concentration of the drugs in plasma; however, a surprising kinetic behavior of the assay was observed with an initial rapid change in apparent FRET values. We found that protein-induced fluorescent enhancement or quenching (PIFE/Q) caused the initial change in fluorescence within the first minute after addition of protein, which could be exploited to construct assays for concentration determination within minutes in the low nanomolar range in plasma. A kinetic model for the assay was established, and when taking the new finding into account, the in silico simulations were in good agreement with the experimentally observed results. Utilizing these findings, a simpler assay was constructed for detection of dabigatran, which allowed for detection within minutes without any time dependencies.

Effects of uninterrupted dabigatran on the intensity of anticoagulation during atrial fibrillation ablation

BACKGROUND

Uninterrupted dabigatran during atrial fibrillation (AF) ablation is now established as the standard therapy. However, there are few reports on the effects of uninterrupted dabigatran on the intensity of anticoagulation during AF ablation.

METHODS

We retrospectively analyzed 247 consecutive patients who underwent AF ablation in our hospital from January 2017 to December 2018. Patients who took warfarin or uninterrupted direct oral anticoagulants (DOACs) except for dabigatran were excluded. 89 patients underwent ablation with uninterrupted dabigatran (uninterrupted group, male 71, mean age 59.6 ± 14.0) and 124 with interrupted DOACs (interrupted group, male 105, mean age 56.9 ± 12.9) during AF ablation. The initial ACT level, proportion of ACT levels of more than 300 s, and total amount of heparin were compared. Furthermore, the incidence of procedure complications was also evaluated.

RESULTS

The initial ACT levels were significantly higher in the uninterrupted group, and the total number of ACTs of more than 300 s was significantly higher in the uninterrupted group (uninterrupted vs. interrupted; initial ACT level, 315.6 ± 59.8 vs. 264.5 ± 48.6, p < .001; total number of ACTs ≧300, n [%], 304/ 484 [62.8 %] vs. 372/745 [49.9%], p < .001). The total amount of heparin during procedure was significantly lower in the uninterrupted group (uninterrupted group vs. interrupted group; 12966 ± 4773 vs. 16371 ± 5212, p < .001). There was no significant difference in the incidence of complications between the two groups.

CONCLUSIONS

In the catheter ablation of AF, uninterrupted dabigatran would be useful to obtain a stable anticoagulation status during the entire procedure.

International multicenter, multiplatform study to validate Taipan snake venom time as a lupus anticoagulant screening test with ecarin time as the confirmatory test: Communication from the ISTH SSC Subcommittee on Lupus Anticoagulant/Antiphospholipid Antibodies

BACKGROUND

Lupus anticoagulant (LA) assays are compromised in anticoagulated patients, and existing strategies to overcome the interferences have limitations. The prothrombin-activating Taipan snake venom time (TSVT) screening test and ecarin time (ET) confirmatory test are innately insensitive to vitamin K antagonists (VKA) and direct factor Xa inhibitors (DFXaI).

OBJECTIVES

Validate standardized TSVT/ET reagents for LA detection, in a multicenter, multiplatform study.

PATIENTS/METHODS

Six centers from four countries analyzed samples with TSVT/ET from 81 nonanticoagulated patients with LA, patients with established antiphospholipid syndrome (APS), and proven persistent LA who were either not anticoagulated (n = 120) or were anticoagulated with VKAs (n = 180) or DFXaIs (n = 71). Additionally, 339 nonanticoagulated LA-negative patients, and 575 anticoagulated non-APS patients (172 VKA, 403 DFXaI) were tested. Anticoagulant spiking experiments were performed and 112 samples containing potential interferences (i.e., direct thrombin inhibitors) were tested. Results were evaluated against locally derived cutoffs. Imprecision was evaluated.

RESULTS

Cutoffs were remarkably similar despite use of different analyzers and donor populations. Cutoffs for TSVT ratio, ET ratio, percent correction, and normalized TSVT ratio/ET ratio ranged between 1.08 and 1.10, 1.09 and 1.12, 9.3% and 14.8%, and 1.10 and 1.15, respectively. Coefficients of variation for TSVT and ET ratios were ≤5.0%. TSVT/ET exhibited sensitivity, specificity, and negative and positive predictive values of 78.2%/95.0%/86.3%/91.5%, respectively, with established APS as the LA-positive population, and 86.9%/95.0%/76.8%/97.4%, respectively, with triple-positive APS. Interference was seen with direct thrombin inhibitors, unfractionated heparin, and low molecular weight heparins, but not VKAs or DFXaIs.

CONCLUSIONS

TSVT/ET are validated for LA detection in nonanticoagulated patients and those on VKAs or DFXaIs.

Acute Stroke Treatment in an Anticoagulated Patient: When Is Thrombolysis an Option?

Purpose of Review

Direct oral anticoagulants (DOACs: the factor Xa inhibitors rivaroxaban, apixaban, and edoxaban and the direct thrombin inhibitor dabigatran) are the mainstay of stroke prevention in patients with non-valvular atrial fibrillation (AF). Nevertheless, there is a residual stroke risk of 1–2% per year despite DOAC therapy. Intravenous thrombolysis (IVT) reduces morbidity in patients with ischemic stroke and improves functional outcome. Prior DOAC therapy is a (relative) contraindication for IVT but emerging evidence supports its use in selected patients.

Recent Findings

Recent observational studies highlighted that IVT in patients on prior DOAC therapy seems feasible and did not yield major safety issues. Different selection criteria and approaches have been studied including selection by DOAC plasma levels, non-specific coagulation assays, time since last intake, and prior reversal agent use. The optimal selection process is however not clear and most studies comprised few patients.

Summary

IVT in patients taking DOAC is a clinically challenging scenario. Several approaches have been proposed without major safety issues but current evidence is weak. A patient-oriented approach balancing potential benefits of IVT (i.e., amount of salvageable penumbra) against expected bleeding risk including appropriate monitoring of anticoagulant activity seem justified.

Automated Thrombin Generation Assay for Rivaroxaban, Apixaban, and Edoxaban Measurements

Background: The thrombin generation assay (TG) is a promising approach to measure the degree of anticoagulation in patients treated with direct oral anticoagulants (DOAC). A strong association with plasma drug concentrations would be a meaningful argument for the potential use to monitor DOAC. Objectives: We aimed to study the correlation of TG with rivaroxaban, apixaban, and edoxaban drug concentrations in a large, prospective multicenter cross-sectional study. Methods: Five-hundred and fifty-nine patients were included in nine tertiary hospitals. The Technothrombin® TG was conducted in addition to an anti-Xa assay; LC-MS/MS was performed as the reference standard. Results: Correlation (r_s) between thrombin generation measurements and drug concentrations was -0.72 for peak thrombin generation (95% confidence interval, CI, -0.77, -0.66), -0.55 for area under the curve (AUC; 95% CI -0.61, -0.48), and 0.80 for lag time (95% CI 0.75, 0.84). In contrast, r_s was 0.96 with results of the anti-Xa activity (95% CI 0.95-0.97). Sensitivity with regard to the clinically relevant cut-off value of 50 μgL^-1 was 49% in case of peak thrombin generation (95% CI, 44, 55), 29% in case of AUC (95% CI, 24, 34), and 64% in case of lag time (95% CI, 58, 69). Sensitivity of the anti-Xa assay was 95% (95% CI, 92, 97). Conclusions: The correlation of thrombin generation measurements with DOAC drug concentrations was weak, and clinically relevant drug levels were not predicted correctly. Our results do not support an application of TG in the monitoring of DOAC.

Strategies for the prevention and treatment of bleeding in patients treated with dabigatran: an update

INTRODUCTION

Although dabigatran is safer than vitamin K antagonists, bleeding still occurs. Bleeding is an important cause of short-term morbidity and rarely mortality and can also have long-term consequences that are often under-appreciated. After bleeding, patients often do not restart treatment or are poorly adherent, which is associated with increased thromboembolism and mortality. Consequently, we need strategies to prevent and treat bleeding in patients with atrial fibrillation treated with dabigatran.

AREAS COVERED

We review a) relevant dabigatran pharmacology, b) the burden and consequences of bleeding, c) how to identify patients at high risk of bleeding; and d) existing and novel approaches to prevent and treat bleeding in dabigatran-treated patients.

EXPERT OPINION

Concerns about the risk of bleeding associated with anticoagulant therapy and emerging evidence of increased risk of thromboembolism and mortality after bleeding highlight the need for improved approaches to prevention and treatment of bleeding. Future research priorities should focus on improving our ability to prevent bleeding by identifying modifiable risk factors and the development of safer agents. The current front runners include drugs that selectively target the contact pathway of coagulation (e.g. factor XI). Targeting upstream drivers of thrombosis (e.g. inflammation) could help to further reduce the risk of thromboembolism.

Point-of-care testing of coagulation in patients treated with edoxaban

Edoxaban, alongside other direct oral anticoagulants (DOAC), is increasingly used for prevention of thromboembolism, including stroke. Despite DOAC therapy, however, annual stroke rate in patients with atrial fibrillation remains 1–2%. Rapid exclusion of relevant anticoagulation is necessary to guide thrombolysis or reversal therapy but, so far, no data exists on the effect of edoxaban on available point-of-care test systems (POCT). To complete our previous investigation on global coagulation-POCT for the detection of DOAC, we evaluated whether CoaguChek®-INR (CC-INR) is capable of safely ruling out edoxaban concentrations above the current treatment thresholds of 30/50 ng/mL in a blood sample. We studied patients receiving a first dose of edoxaban; excluding subjects receiving other anticoagulants. Six blood samples were collected from each patient: before drug intake, 0.5, 1, 2 and 8 h after intake, and at trough (24 h). CC-INR and mass spectrometry for edoxaban concentrations were performed for each time-point. One hundred and twenty blood samples from 20 patients contained 0–302 ng/mL of edoxaban. CC-INR ranged from 0.9 to 2.3. Pearson’s correlation coefficient showed strong correlation between CC-INR and edoxaban concentrations (r = 0.73, p < 0.001). Edoxaban concentrations > 30 and > 50 ng/mL were ruled out by CC-INR ≤ 1.0 and ≤ 1.1, respectively, with high specificity (> 95%), and a sensitivity of 44% (95%-confidence interval: 30–59%) and 86% (74–93%), respectively. Our study represents the first evaluation of coagulation-POCT in edoxaban-treated patients. CC-POCT is suitable to safely exclude clinically relevant edoxaban concentrations prior to thrombolysis, or guide reversal therapy in stroke patients.

Use of direct oral anticoagulants in patients with obesity for treatment and prevention of venous thromboembolism: Updated communication from the ISTH SSC Subcommittee on Control of Anticoagulation

Although direct-acting oral anticoagulants (DOACs) have widespread first-line use for treatment and prevention of venous thromboembolism (VTE), uncertainty remains regarding their efficacy and safety in patients with obesity. We reviewed available data for use of DOACs for VTE treatment and prevention in patients with obesity, including phase 3, phase 4, meta-analyses, and pharmacokinetic and pharmacodynamics studies. In addition, we reviewed available data regarding DOACs in bariatric surgery. We provide updated guidance recommendations on using DOACs in patients with obesity for treatment and prevention of VTE, as well as following bariatric surgery.

Updated recommendations for the treatment of venous thromboembolism

Venous thromboembolism (VTE), which includes pulmonary embolism and deep vein thrombosis, is a condition characterized by abnormal blood clot formation in the pulmonary arteries and the deep venous vasculature. It is often serious and sometimes even fatal if not promptly and appropriately treated. Moreover, the later consequences of VTE may result in reduced quality of life. The treatment of VTE depends on various factors, including the type, cause, and patient comorbidities. Furthermore, bleeding may occur as a side effect of VTE treatment. Thus, it is necessary to carefully weigh the benefits versus the risks of VTE treatment and to actively monitor patients undergoing treatment. Asian populations are known to have lower VTE incidences than Western populations, but recent studies have shown an increase in the incidence of VTE in Asia. A variety of treatment options are currently available owing to the introduction of direct oral anticoagulants. The current VTE treatment recommendation is based on evidence from previous studies, but it should be applied with careful consideration of the racial, genetic, and social characteristics in the Korean population.

Point-of-care testing for emergency assessment of coagulation in patients treated with direct oral anticoagulants including edoxaban

BACKGROUND

Direct oral anticoagulants (DOAC) including edoxaban are increasingly used for stroke prevention in atrial fibrillation. Despite treatment, annual stroke rate in these patients remains 1-2%. Rapid assessment of coagulation would be useful to guide thrombolysis or reversal therapy in this growing population of DOAC/edoxaban-treated stroke patients. Employing the Hemochron™ Signature Elite point-of-care test system (HC-POCT), clinically relevant plasma concentrations of dabigatran and rivaroxaban can be excluded in a blood sample. However, no data exists on the effect of edoxaban on HC-POCT results. We evaluated whether edoxaban plasma concentrations above the current treatment thresholds for thrombolysis or anticoagulation reversal (i.e., 30 and 50 ng/mL) can be ruled out with the HC-POCT.

METHODS

We prospectively studied patients receiving a first dose of edoxaban. Six blood samples were collected from each patient: before, 0.5, 1, 2, 8, and 24 h after drug intake. HC-POCT-based INR (HC-INR), activated clotting time (HC-ACT+ and HC-ACT-LR), activated partial thromboplastin time (HC-aPTT), and mass spectrometry for edoxaban plasma concentrations were performed at each time-point. We calculated correlations, receiver operating characteristics (ROC) and test-specific cut-offs for ruling out edoxaban concentrations > 30 and > 50 ng/mL in a blood sample.

RESULTS

One hundred twenty blood samples from 20 edoxaban-treated patients were analyzed. Edoxaban plasma concentrations ranged from 0 to 512 ng/mL. HC-INR/HC-ACT+/HC-ACT-LR/HC-aPTT ranged from 0.7-8.3/78-310 s/65-215 s/19-93 s, and Pearson's correlation coefficients showed moderate to very strong correlations with edoxaban concentrations (r = 0.95/0.79/0.70/0.60). With areas under the ROC curve of 0.997 (95% confidence interval: 0.991-0.971) and 0.989 (0.975-1.000), HC-INR most reliably ruled out edoxaban concentrations > 30 and > 50 ng/mL, respectively, and HC-INR results ≤1.5 and ≤ 2.1 provided specificity/sensitivity of 98.6% (91.2-99.9)/98.0% (88.0-99.9) and 96.8% (88.0-99.4)/96.5% (86.8-99.4).

CONCLUSIONS

Our study represents the first systematic evaluation of the HC-POCT in edoxaban-treated patients. Applying sufficiently low assay-specific cut-offs, the HC-POCT may not only be used to reliably rule out dabigatran and rivaroxaban, but also very low edoxaban concentrations in a blood sample. Because the assay-specific cut-offs were retrospectively defined, further investigation is warranted.

TRIAL REGISTRATION

ClinicalTrials.gov, registration number: NCT02825394 , registered on: 07/07/2016, URL.

Direct Oral Anticoagulants Plasma Levels Measurement: Clinical Usefulness from Trials and Real-World Data

Measurement of direct oral anticoagulants (DOACs) activity is not routinely necessary. Indeed, evaluation of DOACs plasmatic concentration is discouraged for the majority of patients, due to the lack of outcome data supporting this approach. Nevertheless, DOAC measurements may be useful in emergency situations such as serious bleeding events, need for urgent invasive procedures, and acute ischemic stroke or in managing anticoagulation in "special populations" not adequately studied in clinical trials, for example the very elderly or those at the extremes of body weight. The aim of this review is to describe and summarize the methods for DOACs activity evaluation and the settings in which their plasma level measurement may be indicated, analyzing indications from scientific societies and evidence from clinical trials, as well as real world data on the usefulness of DOACs plasma levels "monitoring."

Influence of PAR-1 in patients with non-valvular atrial fibrillation: The antiplatelet effect of dabigatran

INTRODUCTION

Dabigatran, a direct thrombin inhibitor, has been widely used in patients with non-valvular atrial fibrillation (NVAF) and is considered to have an antiplatelet effect. However, the mechanisms remain unclear. We evaluated protease-activated receptor-1 (PAR-1) expression and activation by thrombin on platelets from NVAF patients, before and after dabigatran treatment, in addition to the expression of platelet activation marker CD62P.

MATERIALS AND METHODS

The study included 18 NVAF patients. We used flow cytometry to measure the binding of PAR-1 monoclonal antibodies (SPAN12 and WEDE15) and the expression of CD62P with and without thrombin stimulation, before, 14 days after, and 28 days after treatment with dabigatran. Coagulation fibrinolysis markers were also measured.

RESULTS

PAR-1 expression was significantly lower in NVAF patients than in healthy controls (HC); it was further reduced by thrombin stimulation. CD62P expression was almost absent on the platelets in NVAF patients, but was significantly increased by thrombin stimulation. PAR-1 expression was not significantly different before and after treatment; CD62P expression was inhibited by dabigatran. The levels of coagulation markers were significantly higher in NVAF patients than in HC, and decreased after treatment.

CONCLUSIONS

Lower expression of PAR-1 in NVAF patients resulted from the cleavage of PAR-1 on some platelets, by exposure to small amounts of thrombin in vivo. The therapeutic effect of dabigatran in NVAF patients was demonstrated by inhibition of CD62P expression on the platelet upon thrombin stimulation in vitro. Our results indicate that dabigatran may reveal antithrombotic activity with antiplatelet and anticoagulant effects.

Dabigatran Reversal With Idarucizumab in 2 Patients With Portal Vein Thrombosis Undergoing Orthotopic Liver Transplantation

There are limited data to guide the use of anticoagulation in cirrhotic patients prior to liver transplantation especially when using direct oral anticoagulants. In this article, we present 2 cases. The first is a 42-year-old male with cirrhosis complicated by portal vein thrombosis (PVT) treated with dabigatran who underwent orthotopic liver transplantation without complication. The second case is a 65-year-old man with alcoholic cirrhosis complicated by PVT treated with dabigatran who underwent orthotopic liver transplantation and required reoperation for surgical bleeding. Both patients were treated with dabigatran’s reversal agent idarucizumab prior to incision. In this case series, we discuss the treatment of cirrhotic patients with various anticoagulants, considerations for anticoagulant selection and reversal prior to liver transplant, and questions for future investigation.

Effects of rivaroxaban and dabigatran on global hemostasis in patients with atrial fibrillation

: The study was aimed to evaluate the effects of two standard doses of rivaroxaban and dabigatran on global hemostatic assays in patients with atrial fibrillation. The study included 52 patients treated with rivaroxaban (15/20 mg), 50 on dabigatran (110/150 mg) and 20 healthy individuals. Platelet-poor plasma was used for determination of three global hemostatic assays, namely endogenous thrombin potential (ETP), calibrated automated thrombogram (CAT) and overall hemostasis potential (OHP). Rivaroxaban and dabigatran reduced ETP (P < 0.01) although OHP (P < 0.05) was diminished only by dabigatran. Strong correlations were noticed between ETP parameters and the plasma concentrations of rivaroxaban (ETP, r = -0.51; c-max, r = -0.85; t-lag, r = 0.83; t-max, r = 0.66) as well as with plasma concentration of dabigatran (ETP, r = -0.75; c-max, r = -0.74; t-lag, r = 0.73; t-max, r = 0.52). Analysis of dabigatran concentrations under 50 ng/ml showed that ETP parameter has area under the concentration-time curve-receiver operating characteristic value of 0.879 (95% confidence interval 0.776-0.980). Dabigatran treatment paradoxically increased area under the concentration-time curve and peak values although rivaroxaban decreased peak values (P < 0.01). However, significant correlation between CAT parameters and plasma concentration of both direct oral anticoagulants was not observed. We confirmed that the CAT assay is inappropriate for estimation of dabigatran effects and is not fully sensitive as regards rivaroxaban. The ETP assay can potentially be the appropriate method for estimation of global hemostatic capacity as regards both direct oral anticoagulants. The role of OHP needs to be confirmed in additional studies. ETP parameter of chromogenic assay has promising potential in exclusion of high plasma concentrations of dabigatran.

Real-world experience with reversal of dabigatran by idarucizumab

AIMS

Idarucizumab reverses the anticoagulant effect of dabigatran. We aimed to investigate real-world experience with idarucizumab and associated clinical outcomes.

METHODS

We conducted a retrospective observational case series on dabigatran users treated with idarucizumab. Using electronic patient records, we identified patients from December 2015 (market introduction) to 31 December 2019 from the Central Denmark Region, covering approximately 1.3 million inhabitants. Treatment indications included need of acute surgery, major bleeding, dabigatran intoxication and need of thrombolysis. Outcomes were defined according to treatment indication, and adverse events were defined as bleeding, thrombosis or death within 30 days of infusion.

RESULTS

A total of 46 dabigatran users were treated with idarucizumab. All patients except one received dabigatran due to atrial fibrillation. Indications for idarucizumab use were need of acute surgery in 22 (48%), severe bleeding in 20 (43%), dabigatran intoxication in three (7%), and prior to thrombolysis in acute stroke in one (2%) patient. There were no reports of excessive bleeding during surgery in patients reversed just prior to surgery. For patients presenting with severe bleeding, all but one achieved effective haemostasis. Among all patients receiving idarucizumab, six (13%) experienced bleeding within 30 days after infusion. None experienced thromboembolic complications. At 30 days follow-up, 38 (83%) patients were alive of whom 35 (92%) had restarted anticoagulant treatment.

CONCLUSION

This study of real-world application of idarucizumab demonstrated effectiveness in terms of surgery performed without excessive bleeding and cessation of severe bleeding in dabigatran-treated patients. Safety appeared high as no patients experienced thromboembolic complications within 30 days.

Effects of dabigatran and rivaroxaban on stroke severity according to the results of routine coagulation tests

Introduction

Prior use of direct oral anticoagulants has been associated with reduced stroke severity in patients with non-valvular atrial fibrillation (NVAF). The aim of this study was to investigate the impact of prothrombin time (PT) and activated partial thromboplastin time (aPTT) on stroke severity in patients who were receiving dabigatran or rivaroxaban at the time of stroke onset.

Materials and methods

We enrolled 107 patients with NVAF who developed acute ischemic stroke while on dabigatran or rivaroxaban and presented within 24 hours to nine hospitals between January 2014 and December 2018. The results of PT and aPTT assays were obtained within 24 hours of stroke onset in all patients. We analyzed PT and aPTT in relation to stroke severity and ischemic lesion volume using correlation and multivariable regression analyses.

Results

Of the 107 patients included, 46 (43.0%) were on dabigatran and 61 (57.0%) were on rivaroxaban. In patients with prior dabigatran use, while aPTT was inversely correlated with admission National Institutes of Health Stroke Scale (NIHSS) score (r = -0.369, p = 0.012) and ischemic lesion volume (r = -0.480, p = 0.005), there was no correlation between PT and either of these variables. Multivariable analysis confirmed the existence of a significant independent inverse relationship between aPTT and NIHSS score at admission (B, -0.201; 95% confidence interval [CI], -0.370 to -0.032; p = 0.005) and between aPTT and ischemic lesion volume (B, -0.076; 95% CI, -0.130 to -0.023; p = 0.007). In patients with prior rivaroxaban use, neither PT nor aPTT was associated with admission NIHSS score or ischemic lesion volume in the correlation and multivariable analyses.

Conclusions

In patients with NVAF who were receiving dabigatran, prolonged aPTT was associated with reduced stroke severity.

Different Coagulation Indicators in Predicting Clinical Outcomes for Patients With Direct Oral Anticoagulants: A Systematic Review and Meta-analysis

PURPOSE

There are many anticoagulant test indexes available for direct oral anticoagulants (DOACs), but how to select the appropriate index and the index cutoff values are still controversial. This is the first study, to our knowledge, to assess the association of different coagulation indicators with clinical outcomes among DOACs using a meta-analysis of observational studies.

METHODS

A medical literature search was conducted using PubMed, Web of Science, EMBASE, ClinicalTrials.gov, and the Cochrane Library from inception to February 2020. Studies that reported relationships between coagulation indexes and clinical outcomes or the diagnostic value of coagulation assays were included in the analysis.

FINDINGS

A total of 17 articles (7 meta-analyses and 10 systematic reviews) from 8904 citations were included in the analysis. In the analysis of bleeding events with coagulation indexes for DOACs, for peak prothrombin time level (cutoff value of 19-25 s), the pooled results found a sensitivity of 0.61 (95% CI, 0.44-0.75) and a specificity of 0.71 (95% CI, 0.49-0.86). For rivaroxaban, the trough anti-factor Xa concentration (AXA-C) (cutoff value of 400-500 ng/mL) had a sensitivity of 0.53 (95% CI, 0.16-0.87) and a specificity of 0.87 (95% CI, 0.71-0.94), with a diagnostic odds ratio of 7 (95% CI, 2-32). For apixaban, trough AXA-C had a sensitivity of 0.85 (95% CI, 0.60-0.96) and a specificity of 0.83 (95% CI, 0.52-0.95). The AUC of the AXA-C peak was higher than that of the trough AXA-C for apixaban, with a higher sensitivity and specificity. Compared with trough concentration of anti-factor IIa for dabigatran, the peak concentration had a higher specificity (98%) at the cutoff value of 484 ng/mL. In the analysis of thromboembolic events with coagulation indexes for DOACs, peak and trough prothrombin time values were not typically correlated with subsequent symptomatic venous thromboembolism, without a sensitivity or specificity higher than 90%. Trough AXA-C had a sensitivity of 100% and but a low specificity (<50%) for rivaroxaban-apixaban. Trough AXA-C had a sensitivity of 100% and a specificity of 32% with a cutoff value of 108 ng/mL for dabigatran.

IMPLICATION

Peak prothrombin time (19-25 s) and AXA-C had a better predictive value on bleeding outcomes for rivaroxaban and apixaban, whereas peak concentration of anti-factor IIa activity can be an indicator for dabigatran. Coagulation indexes might not be a good indicator of thromboembolic events of DOACs. Because the limited studies focused on association of coagulation indicators and clinical outcomes, more studies are needed to verify this in the future.

Ecarin based coagulation testing

Ecarin is derived from venom of Echis carinatus, and will activate prothrombin into meizothrombin which will then cleave fibrinogen to result in clot formation. Ecarin based testing has been described for decades, but these assays were typically restricted to reference or speciality coagulation laboratories. This test was initially described for the assessment of direct thrombin inhibitors (eg, bivalirudin lepirudin, or argatroban) and was not affected by heparins or heparinoids. Ecarin based assays were rarely used for anticoagulation monitoring until the emergence of the direct oral thrombin inhibitor dabigatran etexilate in 2010. As this test was mentioned in the prescribing information for dabigatran etexilate, there was increased interest for use by clinical laboratories as the preferred method for assessing the anticoagulant effect of this drug. The purpose of this document is to review the current status of ecarin based assays for assessing dabigatran. This is with the understanding that these methods can also be exploited for determining the anticoagulation effect of parenteral direct thrombin inhibitors, such as argatroban and bivalirudin.

Dabigatran Reversal With Idarucizumab in Patients With Renal Impairment

BACKGROUND

Dabigatran and idarucizumab, its reversal agent, are renally cleared.

OBJECTIVES

The purpose of this study was to determine the extent of reversal and outcomes according to baseline renal function in dabigatran-treated nondialysis patients receiving idarucizumab.

METHODS

In 503 patients in RE-VERSE AD (Reversal of Effects of Idarucizumab in Patients on Active Dabigatran), the extent of dabigatran reversal and clinical outcomes were compared according to baseline renal function (creatinine clearance: normal ≥80, mild 50 to <80, moderate 30 to <50, and severe <30 ml/min).

RESULTS

Compared with patients with normal renal function, those with impaired renal function were older, were more often women, and had lower body mass indexes, more comorbidities, higher CHADS₂ scores, and higher dabigatran plasma levels despite more frequent use of lower-dose dabigatran regimens. Regardless of renal function, median reversal measured by dilute thrombin time was 100% within 4 h of idarucizumab administration, and over 98% of patients achieved this with corresponding undetectable levels of unbound dabigatran. By 12 or 24 h, 56% of patients with severe, 29.1% with moderate, and 9.2% with mild renal impairment had dabigatran levels >20 ng/ml compared with 8.3% of patients with normal renal function at baseline. Time to cessation of bleeding and the proportion with normal hemostasis with procedures were similar regardless of renal function, but patients with severe renal impairment had higher 30- and 90-day mortality rates.

CONCLUSIONS

Idarucizumab completely reverses dabigatran in >98% of patients regardless of renal function. Although re-elevation of dabigatran levels within 12 to 24 h is more common with renal impairment, the time to bleeding cessation and the extent of hemostasis during procedures are similar. (Reversal of Dabigatran Anticoagulant Effect With Idarucizumab; NCT02104947).

Bioequivalence and pharmacodynamics of a generic dabigatran etexilate capsule in healthy Chinese subjects under fasting and fed conditions

To assess bioequivalence of a generic dabigatran etexilate capsule in healthy Chinese subjects under fasting and fed conditions. This was an open-label, single-center, randomized four-period crossover study with a 7-day washout period. A single oral dose of 150 mg generic dabigatran etexilate capsule (test drug) or a commercial dabigatran etexilate capsule (Pradaxa® , reference drug) was given to healthy volunteers under the fasting and fed conditions. Plasma concentrations of total and free dabigatran were detected using a validated HPLC-MS/MS method. A noncompartmental method was used for pharmacokinetic analysis and established coagulation assays were applied for pharmacodynamic analysis. The 90% CIs of the test/reference ratios of Cmax , AUC0-t , and AUC0-∞ for the total dabigatran concentration were 92.57%-106.58%, 91.63%-106.32%, and 92.54%-106.17%, respectively, under fasting condition, and 99.30%-110.74%, 98.58%-105.37%, and 97.75%-103.99%, respectively, under fed conditions. The 90% CIs of the ratios of the parameters for the free dabigatran were 93.18%-106.98%, 92.13%-107.10%, 92.89%-106.48%, respectively, under fasting condition, and 100.05%-110.89%, 99.37%-106.23%, 97.59%-103.98%, respectively, under the fed condition. Additionally, the upper limit of the 90% CIs for σWT/σWR was below 2.5. There were no significant differences in the coagulation parameters including thrombin clotting time, activated partial thromboplastin time, and anti-IIa activity between the two preparations. The generic dabigatran etexilate capsule is bioequivalent to the brand-named product in healthy Chinese volunteers under fasting and fed conditions. The two products have comparable pharmacodynamic parameters, with a good safety profile. In addition, food intake influences absorption of both products in a similar way.

Assessing and Reversing the Effect of Direct Oral Anticoagulants on Coagulation

This article presents a focused review of the available tests to assess the effect of direct oral anticoagulants on coagulation and the use of reversal agents in the perioperative setting for practicing anesthesiologists.

The Protective Effect of Dabigatran and Rivaroxaban on DNA Oxidative Changes in a Model of Vascular Endothelial Damage with Oxidized Cholesterol

Background: Atherosclerotic plaques are unstable, and their release may result in thrombosis; therefore, currently, antiplatelet therapy with anticoagulants is recommended for the treatment of acute coronary syndrome. The aim of this study was to assess the effect of oxidized cholesterol on human umbilical vascular endothelial cells (HUVECs). The study also examines the protective and repairing effect of dabigatran and rivaroxaban in a model of vascular endothelial damage with 25-hydroxycholesterol (25-OHC). Methods: HUVECs were treated with compounds induce DNA single-strand breaks (SSBs) using the comet assay. Oxidative DNA damage was detected using endonuclease III (Nth) or human 8 oxoguanine DNA glycosylase (hOOG1). Reactive oxygen species (ROS) formation was determined using flow cytometry. Results: 25-hydroxycholesterol caused DNA SSBs, induced oxidative damage and increased ROS in the HUVECs; ROS level was lowered by dabigatran and rivaroxaban. Only dabigatran was able to completely repair the DNA SSBs induced by oxysterol. Dabigatran was able to reduce the level of oxidative damage of pyrimidines induced by oxysterol to the level of control cells. Conclusions: Observed changes strongly suggest that the tested anticoagulants induced indirect repair of DNA by inhibiting ROS production. Furthermore, dabigatran appears to have a higher antioxidant activity than rivaroxaban.

Limitations of Specific Coagulation Tests for Direct Oral Anticoagulants: A Critical Analysis

Background

During treatment with direct oral anticoagulants (DOAC), coagulation assessment is required before thrombolysis, surgery, and if anticoagulation reversal is evaluated. Limited data support the accuracy of DOAC‐specific coagulation assays around the current safe‐for‐treatment threshold of 30 ng/mL.

Methods and Results

In 481 samples obtained from 96 patients enrolled at a single center, DOAC concentrations were measured using Hemoclot direct thrombin inhibitor assay, Biophen direct thrombin inhibitor assay or ecarin clotting time for dabigatran, chromogenic anti‐Xa assay (AXA) for factor Xa inhibitors (rivaroxaban, apixaban) and ultraperformance liquid chromatography–tandem mass spectrometry as reference. All dabigatran‐specific assays had high sensitivity to concentrations >30 ng/mL, but specificity was lower for Hemoclot direct thrombin inhibitor assay (78.2%) than for Biophen direct thrombin inhibitor assay (98.9%) and ecarin clotting time (94.6%). AXA provided high sensitivity and specificity for rivaroxaban, but low sensitivity for apixaban (73.8%; concentrations up to 82 ng/mL were misclassified as <30 ng/mL). If no DOAC‐specific calibration for AXA is available, results 2‐fold above the upper limit of normal indicate relevant rivaroxaban concentrations. For apixaban, all elevated results should raise suspicion of relevant anticoagulation.

Conclusions

DOAC‐specific tests differ considerably in diagnostic performance for concentrations close to the currently accepted safe‐for‐treatment threshold. Compared with Biophen direct thrombin inhibitor assay and ecarin clotting time, limited specificity of Hemoclot direct thrombin inhibitor assay poses a high risk of unnecessary anticoagulation reversal or treatment delays in patients on dabigatran. While AXA accurately detected rivaroxaban, the impact of low apixaban levels on the assay was weak. Hence, AXA results need to be interpreted with extreme caution when used to assess hemostatic function in patients on apixaban.

Clinical Trial Registration

URL: https://www.clinicaltrials.gov. Unique identifiers: NCT02371044, NCT02371070.

Idarucizumab for Reversal of Dabigatran in Early/Emergency Surgeries: A Case Series

BACKGROUND

Idarucizumab is a humanized, monoclonal antibody fragment used specifically to reverse the anticoagulant effects of dabigatran.

CASE REPORTS

We discuss 4 cases of patients who were treated with idarucizumab to reverse dabigatran before early/emergency surgery. Two of the patients had subdural hematomas, 1 had a splenic laceration, and 1 had Fournier gangrene. All patients received 5 g of idarucizumab before surgery. Intraoperative blood loss in all patients was normal, no adverse events were reported, and the patients recovered normally. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: The case reports presented provide detailed, practical, real-world experience beyond that reported in other case reports and the Reversal Effects of Idarucizumab on Active Dabigatran study. This can help guide clinicians on how idarucizumab can reverse the anticoagulant effect of dabigatran in emergency situations, including patients with subdural hematoma. Our experience suggests that idarucizumab may be a safe and effective antidote to the effects of dabigatran in real-life bleeding situations involving early or emergency surgeries.

Idarucizumab in major trauma patients: a single centre real life experience

INTRODUCTION

Trauma care providers are facing an increasing number of elderly patients on direct oral anticoagulants prior to injury. For dabigatran etexilate (DAB), the specific antagonist idarucizumab (IDA) has been approved since 2015 as a reversal agent. However, only limited data regarding the use of IDA in trauma patients are available.

METHODS

We performed a retrospective analysis of trauma patients under DAB for whom IDA administration was deemed necessary to reverse DAB's antithrombotic effect.

RESULTS

A total of 15 (9 male) patients were treated with IDA during the study period. The mean age was 81 ± 10 years. Intracranial haemorrhage (n = 7) and long bone fractures (n = 5) were the most common types of injury. Three patients were diagnosed as polytrauma. In all but one patient, atrial fibrillation was the indication for DAB intake. The median dose of IDA was 2.5 g (IQR 2.5-5). IDA administration decreased DAB plasma levels from 112.4 (IQR 73.4-123.4) to 5 (IQR 4-12) ng/mL (p = 0.031), thrombin time from 114.8 ± 48.3 to 16.2 ± 0.5 s (p < 0.0001) and activated partial thromboplastin time form 45.4 ± 11.3 to 34.2 ± 7.0 s (p = 0.0025). No thromboembolic events or side effects attributed to IDA were observed. All patients survived until hospital discharge.

CONCLUSIONS

In trauma patients under DAB prior to injury, IDA decreased DAB plasma levels and normalized coagulation parameters. IDA appears to be safe, and no serious side effects were observed in this small cohort of patients.

Routine Coagulation Tests in Patients With Nonvalvular Atrial Fibrillation Under Dabigatran and Rivaroxaban Therapy: An Affordable and Reliable Strategy?

Dabigatran and rivaroxaban, direct oral anticoagulants (DOACs), affect coagulation tests, and knowledge of their effects is important for therapeutic monitoring. Our aim was to examine the association between DOAC levels and routine coagulation tests in patients with nonvalvular atrial fibrillation. Samples from patients receiving dabigatran (150 mg) and patients receiving rivaroxaban (20 mg) were collected 2 hours after drug intake. Direct oral anticoagulant concentrations were determined using direct Hemoclot thrombin inhibitor (HTI) assay (HTI test) and a direct Xa inhibitor (Anti Xa-Riva). The routine coagulation measured included activated partial thromboplastin time (aPTT) and prothrombin time (PT). The median plasmatic dabigatran was 128.3 ng/mL (95% confidence interval [CI]: 93.7-222.6 ng/mL). The HTI exhibited a good correlation with aPTT (R² = 0.74; P < .0001). The median plasmatic rivaroxaban was 223.9 ng/mL (95% CI: 212.3-238.9 ng/mL). Anti-Xa-Riva correlated with PT (R² = 0.69, P< .0001) and aPTT (R² = 0.36, P < .001), but prolonged PT results were obtained, even below the rivaroxaban therapeutic range (20%). The routine coagulation tests were able to identify out of therapeutic range concentrations for dabigatran and rivaroxaban. We suggest the use of these screening tests to better understand and monitor the subtherapeutic concentrations of these DOACs.

Factors affecting serum concentration of dabigatran in Asian patients with non-valvular atrial fibrillation

BACKGROUND/PURPOSE

Dabigatran is effective in preventing ischemic stroke and systemic embolism in patients with atrial fibrillation. Although the therapeutic window for dabigatran is wide, its pharmacokinetic properties can differ between specific populations. This study aimed to establish a real-life plasma dabigatran concentration database and investigate potential factors affecting this concentration in Asians.

METHODS

Patients under dabigatran therapy were recruited. Plasma dabigatran concentration was determined in trough and peak blood samples by using ultra-high performance liquid chromatography with tandem mass spectrometry analysis. Factors affecting the dabigatran concentration were investigated.

RESULTS

A total of 46 patients (33 male, 71.7%) were prospectively enrolled. Most of them were receiving a low dose regimen (110 mg twice daily, n = 38, 82.6%). The trough and peak concentrations were significantly correlated (p < 0.001), and the trough concentration was higher in patients aged ≥75 years, body weight ≤60 kg, creatinine clearance (CrCl) ≤50 mL/min, CHA₂DS₂-VASc score >3 points, and HAS-BLED score ≥3 points. Multiple linear regression analysis identified body weight and serum creatinine as key factors predicting trough concentration (p = 0.003 and 0.005, respectively). Importantly, drug adherence was the only independent factor associated with low trough concentration, defined as the lowest 20th percentile in our study cohort (n = 10, hazard ratio = 9.07; 95% CI, 1.12 to 73.22; p = 0.004).

CONCLUSION

Dabigatran monitoring may be considered for patients at risk of overexposure, especially those with low body weight and renal insufficiency, and also for detecting those with extremely low drug concentration.

The impact of prothrombin complex concentrates when treating DOAC-associated bleeding: a review

Background

Bleeding complications are a risk associated with all anticoagulants. Currently, the treatment options for the management of direct oral anticoagulant (DOAC)-associated bleeding are limited. Prothrombin complex concentrates (PCCs) have been proposed as a potential therapeutic option, and evidence regarding their use is increasing.

Review

Many studies supporting PCC have used preclinical models and healthy volunteers; however, more recently, observational studies have further improved insight into current DOAC reversal strategies. Multiple clinical practice guidelines now specifically suggest use of PCCs for this indication. Specific reversal agents for Factor Xa inhibitors may become available in the near future, but data on their efficacy are still emerging.

Conclusions

Ultimately, a multimodal approach may be the optimal strategy to restore haemostasis in patients presenting with DOAC-associated coagulopathy.

Electronic supplementary material

The online version of this article (10.1186/s12245-018-0215-6) contains supplementary material, which is available to authorized users.

Rapid determination of anticoagulating effects of dabigatran in whole blood with rotational thromboelastometry and a thrombin-based trigger

Essentials A rapid test to detect thrombin inhibition by dabigatran would be valuable in acute situations. A thrombin-based trigger was applied in whole blood using rotation thromboelastometry. Effects of dabigatran were assessed in vitro and in samples from patients on dabigatran. The test produced data rapidly and was sensitive to dabigatran concentrations from 20 to 500 ng mL-1 . SUMMARY: Background Rapid determination of the anticoagulant effect of dabigatran is essential in emergency situations. Objective To study a viscoelastic test (rotational thromboelastometry [ROTEM]) for rapid determination of dabigatran effects in whole blood samples. Method ROTEM measurements were performed with comparison of two triggers (thrombin-based versus the commercial tissue factor-based trigger Ex-tem) in samples from 10 healthy donors spiked with dabigatran (20-500 ng mL-1 ) and in samples from 35 patients receiving dabigatran treatment; 10 healthy subjects served as controls. Clotting time (CT) and the difference in CT without versus with addition of the dabigatran antidote idarucizumab (CTdiff ) were measured. Addition of idarucizumab reveals the contribution of dabigatran to ROTEM measurements and its potential reversibility. Results In vitro studies showed that thrombin CT and thrombin CTdiff were more sensitive than Ex-tem CT and Ex-tem CTdiff in detecting dabigatran in whole blood samples. In patient samples, when thrombin CT and thrombin CTdiff were used, it was possible to detect dabigatran with a cut-off of dabigatran at 20 ng mL-1 , whereas, when Ex-tem CT and Ex-tem CTdiff were used, the method was less sensitive. Data from patient samples were obtained within 15 min of blood sampling. Conclusions ROTEM CT with a thrombin-based trigger is more sensitive to dabigatran effects than Ex-tem CT, and detects anticoagulant effects of drug concentrations in the low-very low therapeutic range. Analysis with idarucizumab (CTdiff ) reveals dabigatran-specific effects. As data are rapidly obtained, this method could, with further development and validation of its performance, be suitable for detecting clinically significant dabigatran effects in emergency situations.

Testing and monitoring direct oral anticoagulants

Direct oral anticoagulants (DOACs) have significantly improved the care of patients requiring anticoagulation. With similar or better efficacy and safety outcomes and easier use in the outpatient setting compared with the standard-of-care vitamin K antagonists and low molecular weight heparin, DOACs are now endorsed as first-line treatment of indications including prevention of stroke and systemic embolism in nonvalvular atrial fibrillation and treatment of venous thromboembolism. DOACs are easy-to-use oral agents that offer simple dosing and short half-lives, with no need to test levels because of the wide therapeutic window and limited drug-drug interactions. After almost a decade of DOAC use, the question of testing DOAC levels in certain clinical situations has become the focus of debate. Although guidance for using routine coagulation tests is available, these tests are inadequate for optimal care. DOAC-specific tests have been developed but have limited availability in Europe and less availability in the United States. None are licensed. DOAC testing may be useful in the setting of critical clinical situations such as life-threatening bleeding or need for emergent surgery, especially with the availability of DOAC reversal agents. Patients with characteristics that fall outside the normal range may benefit from the guidance that DOAC testing could offer. Obstacles to adopting DOAC testing have been raised, such as test reliability and staffing costs; however, these problems are rapidly being resolved. Further investigation of the role of DOAC testing is needed to explore its full potential and role in clinical practice.

Anticoagulation at the extremes of body weight: choices and dosing

INTRODUCTION

The landscape of therapeutic anticoagulation has changed dramatically over the past decade, with availability of direct oral anticoagulants (DOACs), which inhibit factor Xa or thrombin. However, the optimal anticoagulant agent and dosing strategy for patients at both extremes of body weight has not been established for any anticoagulant, including DOACs, vitamin K antagonists (VKA), and the various heparin options. Areas covered: This paper reviews available evidence to assist clinicians in prescribing of anticoagulation therapy at the extremes of body weight. Expert commentary: There are limited data to guide prescribing of all available anticoagulants at the extremes of weight and further research regarding efficacy and safety outcomes in these groups is required. Laboratory monitoring to guide dosing of traditional anticoagulants provides reassurance of 'predictable' efficacy. In contrast agents that are not routinely monitored by laboratory testing provide greater challenges. For example, underweight patients are at risk of receiving higher drug exposures of DOACs, whereas the use of fixed dose DOACs in obese patients may be associated with lower drug exposures.

Anticoagulation in atrial fibrillation with factor X deficiency-A management dilemma

Factor X (FX) deficiency is a rare bleeding disorder. There is currently no clear guideline or recommendation for the appropriate selection of anticoagulation and management of patients with FX deficiency who require anticoagulation. We shared our experience in managing such patient, and we further discussed other possible treatment options.