Jonathan Douxfils

Impact of dabigatran on a large panel of routine or specific coagulation assays. Laboratory recommendations for monitoring of dabigatran etexilate.

Due to low bioavailability and high inter-individual variability, monitoring of dabigatran may be required in specific situations to prevent the risk of bleedings or thrombosis. The aim of the study was to determine which coagulation assay(s) could be used to assess the impact of dabigatran on secondary haemostasis. Dabigatran was spiked at concentrations ranging from 4.7 ng/ml to 943.0 ng/ml in pooled citrated human platelet-poor plasma. The following clotting assays were performed: prothrombin time (PT); activated partial thromboplastin time (aPTT); thrombin time (TT); ecarin clotting time (ECT); ecarin chromogenic assay (ECA); prothrombinase-induced clotting time (PiCT); activated clotting time (ACT); Hemoclot Thrombin Inhibitor (HTI) and thrombin generation assay (TGA). A concentration-dependent prolongation of PT, dPT, and aPTT was observed with aPTT being the more sensitive test. The results varied mostly due to the clotting reagent. HTI, ECT and TGA were the most sensitive tests but are not available 24 hours a day. In addition, HTI showed a linear correlation with a good reproducibility. Dabigatran induced a concentration-dependent delay and inhibition of tissue factor-induced TGA. Cut-offs related with higher risk of bleedings or thrombosis were defined for each reagent of aPTT and HTI. In conclusion, aPTT could be used for the monitoring of dabigatran and as screening test for the risk of overdose. However, because of its higher sensitivity, good reproducibility, excellent linear correlation at all doses, its simplicity of use, and possibilities of automation, HTI should be considered as the gold-standard.

Assessment of the impact of rivaroxaban on coagulation assays: Laboratory recommendations for the monitoring of rivaroxaban and review of the literature

INTRODUCTION Rivaroxaban does not require monitoring nor frequent dose adjustment. However, searching for the optimal dose in the individual patient may be useful in some situations. AIM To determine which coagulation assay could be used to assess the impact of rivaroxaban on haemostasis and provide guidelines for the interpretation of routine lab tests. MATERIALS Rivaroxaban was spiked at concentrations ranging from 11 to 1,090 ng/mL in plateletpoor plasma. A large panel of coagulation assays was tested. RESULTS A concentration dependent prolongation of aPTT, PT, dPT, PiCT was observed. PT and dPT were the most sensitive chronometric assays but results varied depending on the reagent (Triniclot PT Excel S>Recombiplastin 2G>Neoplastin R>Neoplastin CI+>Triniclot PT Excel>Triniclot PT HTF>Innovin). FXa chromogenic assays showed the highest sensitivity. In TGA, Cmax was the most sensitive parameter with the tissue factor induced pathway. Rivaroxaban interferes on haemostasis diagnostic tests such the measurement of clotting factors, fibrinogen, antithrombin, proteins C and S, activated protein-C resistance and Xa-based chomogenic assays. CONCLUSIONS PT may be used as screening test to assess the risk of bleedings. A more specific and sensitive assay such as Biophen DiXaI using calibrators should be used to confirm the concentration of rivaroxaban. We also propose cut-off associated with a bleeding or thrombosis risk based on pharmacokinetic studies. Standardization of the time between the last intake of rivaroxaban and the sampling is mandatory.

Impact of apixaban on routine and specific coagulation assays: a practical laboratory guide

Apixaban does not require monitoring nor frequent dose adjustment. However, searching for the optimal dose for the individual patient may be useful in some situations. Moreover, there is a need for clinicians to know whether coagulation assays are influenced by apixaban use. The aim of this study was to determine which coagulation assay could be used to assess the impact of apixaban on haemostasis and provide good laboratory recommendations for the accurate interpretation of haemostasis assays. Apixaban is spiked at concentrations ranging from 5 to 500 ng/mlin platelet-poor plasma. Routinely used or more specific coagulation assays are tested. Results show a concentration dependent prolongation of aPTT, PT and dilute PT. The sensitivity mainly depends on the reagent, but none of these tests is sensitive enough to ensure an accurate estimation of the pharmacodynamic effect of apixaban. FXa chromogenic assays show high sensitivity and a linear correlation depending on the reagent and/or the methodology. Immunological assays and assays acting below the FXa are not influenced by apixaban. In conclusion, PT and/or dilute PT cannot be used to assess apixaban pharmacodynamic properties. More specific and sensitive assays such as chromogenic FXa assays using specific calibrators are required. In case of thrombophilia or in the exploration of a haemorrhagic event, immunological assays should be recommended, when applicable. Standardisation of the time between the last intake of apixaban and the sampling is mandatory.

Comparison of calibrated chromogenic anti-Xa assay and PT tests with LC-MS/MS for the therapeutic monitoring of patients treated with rivaroxaban

Possibilities to monitor rivaroxaban therapy could be useful in certain circumstances. Prothrombin time (PT) or chromogenic anti-Xa assays such as the Biophen Direct Factor Xa Inhibitor® (DiXaI) have been proposed to estimate rivaroxaban concentrations but are mainly based on in vitro studies. The study aim was to compare PT and Biophen DiXaI® measurements with liquid chromatography-tandem mass spectrometry (LC-MS/MS) measurements in plasma samples from patients treated with Xarelto®. Fifty-two plasma samples were included. PT was performed using Innovin® and Triniclot PT Excel S®. Biophen DiXaI® was performed according to instructions from the manufacturer. The rivaroxaban plasma concentration ranged between 0 and 485 ng/ml as measured by LC-MS/MS. The limits of quantification were 30 ng/ml and 5 ng/ml for Biophen DiXaI® and LC-MS/MS, respectively. The linear correlation between Biophen DiXaI® and LC-MS/MS analyses was high for all rivaroxaban concentrations (r² = 0.95). For concentrations ≤100 ng/ml, r²-value was 0.83. The Bland-Altman analysis showed a mean difference of -16 ng/ml (SD: 25 ng/ml). The PT methods did not correlate well with plasma concentrations measured by LC-MS/MS (r² ≈ 0.60). In conclusion, the important inter-individual variability and the poor correlation with LC-MS/MS preclude the use of PT to estimate rivaroxaban concentrations. Thanks to its small inter-individual variability and good agreement with LC-MS/MS measurements, we recommend the use of Biophen DiXaI® assays to estimate concentrations of rivaroxaban >30 ng/ml. Quantification of low rivaroxaban levels (<30 ng/ml) requires the LC-MS/MS method.

Dabigatran Etexilate and Risk of Myocardial Infarction, Other Cardiovascular Events, Major Bleeding, and All-Cause Mortality: A Systematic Review and Meta-analysis of Randomized Controlled Trials

Background Signals of an increased risk of myocardial infarction (MI) have been identified with dabigatran etexilate in randomized controlled trials (RCTs). Methods and Resules We conducted searches of the published literature and a clinical trials registry maintained by the drug manufacturer. Criteria for inclusion in our meta‐analysis included all RCTs and the availability of outcome data for MI, other cardiovascular events, major bleeding, and all‐cause mortality. Among the 501 unique references identified, 14 RCTs fulfilled the inclusion criteria. Stratification analyses by comparators and doses of dabigatran etexilate were conducted. Peto odds ratio (ORPETO) values using the fixed‐effect model (FEM) for MI, other cardiovascular events, major bleeding, and all‐cause mortality were 1.34 (95% CI 1.08 to 1.65, P=0.007), 0.93 (95%CI 0.83 to 1.06, P=0.270), 0.88 (95% CI 0.79 to 0.99, P=0.029), and 0.89 (95% CI 0.80 to 1.00, P=0.041). When compared with warfarin, ORPETO values using FEM were 1.41 (95% CI 1.11 to 1.80, P=0.005), 0.94 (95%CI 0.83 to 1.06, P=0.293), 0.85 (95% CI 0.76 to 0.96, P=0.007), and 0.90 (95% CI 0.81 to 1.01, P=0.061), respectively. In RCTs using the 150‐mg BID dosage, the ORPETO values using FEM were 1.45 (95% CI 1.11 to 1.91, P=0.007), 0.95 (95% CI 0.82 to 1.09, P=0.423), 0.92 (95% CI 0.81 to 1.05, P=0.228), and 0.88 (95% CI 0.78 to 1.00, P=0.045), respectively. The results of the 110‐mg BID dosage were mainly driven by the RE‐LY trial. Conclusions This meta‐analysis provides evidence that dabigatran etexilate is associated with a significantly increased risk of MI. This increased risk should be considered taking into account the overall benefit in terms of major bleeding and all‐cause mortality.

Influence of dabigatran and rivaroxaban on routine coagulation assays. A nationwide Belgian survey.

The Belgian national External Quality Assessment Scheme performed a nationwide survey using lyophilised plasma samples spiked with dabigatran or rivaroxaban to demonstrate to the Belgian clinical laboratories how these drugs affect their routine coagulation assays prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen and antithrombin. Virtually all Belgian laboratories performing routine coagulation testing (189/192) participated in the survey. Both, dabigatran and rivaroxaban significantly prolonged the PT and aPTT in a concentration- and reagent-dependent manner. PT reagents were more influenced by rivaroxaban than by dabigatran and aPTT reagents more influenced by dabigatran than by rivaroxaban. Among PT reagents, Neoplastin R® was the most sensitive to rivaroxaban and Innovin® and Thromborel S® the least sensitive. Converting PT results to INR only increased the variability between reagents. Among aPTT reagents, Actin FSL® was the least sensitive to dabigatran while the other aPTT reagents showed slightly higher sensitivities. The presence of dabigatran led to falsely reduced fibrinogen concentrations when measured with a low thrombin concentration reagent. The presence of dabigatran caused an overestimation of the antithrombin level when measured with a thrombin-based activity assay and the presence of rivaroxaban an overestimation of the antithrombin level when measured with a FXa-based assay. Instrument-related differences were found for all tested parameters. In conclusion, this paper provides detailed information on the effect of dabigatran and rivaroxaban on routine coagulation assays as performed with a large number of reagent/instrument combinations.

Estimation of dabigatran plasma concentrations in the perioperative setting. An ex vivo study using dedicated coagulation assays.

The perioperative management of dabigatran is challenging, and recommendations based on activated partial thromboplastin time (aPTT) and thrombin time (TT) are unsatisfactory. Dedicated coagulation tests have limitations at plasma concentrations < 50 ng/ml. Therefore, a more sensitive test, which is available 24/7, is required. It was the aim of this study to investigate the performance of the Hemoclot Thrombin Inhibitors® LOW (HTI LOW) kit, a diluted thrombin time, and the STA® - ECA II(ECA-II) kit, a chromogenic variant of the ecarin clotting time, that were developed to measure low dabigatran concentrations, compared to reference dabigatran analysis by liquid chromatography tandem mass-spectrometry (LC-MS/MS). This study included 33 plasma samples from patients treated with dabigatran etexilate who had plasma concentrations < 200 ng/ml. HTI LOW and ECA-II were performed along with HTI, aPTT (STA®-C. K.Prest® and SynthasIL®) and TT (STA® - Thrombin). All procedures were performed according to recommendations by the manufacturers. Linear (or curvilinear) correlations and Bland-Altman analyses were calculated. For free dabigatran concentrations < 50 ng/ml, the R² of linear correlations were 0.69, 0.84 and 0.61, with HTI, HTI LOW and ECA-II, respectively. The R² for TT, STA®-C. K.Prest® and SynthasIL® were 0.67, 0.42 and 0.15. For HTI, HTI LOW and ECA-II, Bland-Altman analyses revealed mean differences of -6 ng/ml (95 %CI: -25-14 ng/ml), 1 ng/ml (95 %CI: -18-19 ng/ml) and -1 ng/ml (95 %CI: -25-23 ng/ml), demonstrating that tests dedicated to measuring low concentrations are more accurate than HTI. In conclusion, the use of HTI LOW or ECA-II to assess low plasma dabigatran concentrations is supported by our findings.

Appropriateness of Prescribing Dabigatran Etexilate and Rivaroxaban in Patients With Nonvalvular Atrial Fibrillation A Prospective Study

Background: Direct oral anticoagulants have been developed to address some of the drawbacks of vitamin-K antagonists. However, special attention should be given when using these drugs, especially in patients with renal insufficiency, questionable compliance, and those at high risk of bleeding. Objective: To evaluate the appropriateness of prescribing dabigatran etexilate (DE) and rivaroxaban in patients with nonvalvular atrial fibrillation (NVAF) in real-life clinical practice. Methods: This was a prospective study that included patients presenting to a teaching hospital from April to mid-October 2013, who were taking rivaroxaban or DE for NVAF. Appropriateness of prescribing was evaluated using 9 of the 10 criteria of the Medication Appropriateness Index. The primary outcome measure was the prevalence of inappropriate prescribing. Secondary outcome measures included (a) categories of inappropriateness, (b) prevalence of adverse drug events, and (c) interventions made by a clinical pharmacist to optimize prescribing. Results: A total of 69 patients were evaluated; 16 patients (23%) had 1 inappropriate criterion, and an additional 18 (26%) had more than 1 inappropriate criterion. The most frequent inappropriate criteria were inappropriate choice (28% of patients), wrong dosage (26%), and impractical modalities of administration (26%). An adverse event (AE) was found in 51% of patients (including 8 patients with transient ischemic attack/stroke). The clinical pharmacists performed 48 interventions, and 94% were accepted by the physician. Conclusions: Inappropriate use of DE and rivaroxaban in patients with NVAF is frequent and possibly leads to AEs. Reinforcing education of health care professionals and patients is needed. Collaboration with clinical pharmacists can contribute to better use.

Association Between BCR-ABL Tyrosine Kinase Inhibitors for Chronic Myeloid Leukemia and Cardiovascular Events, Major Molecular Response, and Overall Survival: A Systematic Review and Meta-analysis.

Importance A phase 3 trial with ponatinib in patients with chronic myeloid leukemia (CML) was interrupted due to an important increase of vascular occlusive events. A similar risk was also suspected with nilotinib, another BCR-ABL tyrosine kinase inhibitor (TKI) used in patients with CML. Objective To assess the risk of vascular occlusive events in patients with CML treated by new generations of TKIs and provide an overall assessment of the clinical benefit. Data Sources Two independent reviewers selected studies from PubMed, Scopus, and the Cochrane library database from their inception to October 21, 2014. Abstracts published during the past 3 years at international congresses and a trial register were also searched. Study Selection Two independent reviewers screened abstracts and titles against inclusion and exclusion criteria published previously in the PROSPERO 2014 protocol: CRD42014014147. Among the 249 abstracts identified, 10 studies fulfilled the established criteria. Data Extraction and Synthesis Two investigators independently extracted data using a standard form. Main Outcomes and Measures Information extracted included study and patients characteristics, type of intervention and data on vascular occlusive events, overall survival, and major molecular response (MMR). The meta-analysis was performed using a fixed-effects model. Odds ratios (ORs) with 95% CIs were computed using the Peto method. Results Ten randomized clinical trials (3043 patients) were analyzed. Risk of vascular occlusive events was increased with dasatinib (OR, 3.86; 95% CI, 1.33-11.18), nilotinib (OR, 3.42; 95% CI, 2.07-5.63), and ponatinib (OR, 3.47; 95% CI, 1.23-9.78) compared with imatinib in patients with CML. No significant difference was found with bosutinib (OR, 2.77; 95% CI, 0.39-19.77). New-generation TKIs increased the rate of MMR at 1 year compared with imatinib (overall OR, 2.22; 95% CI, 1.87 to 2.63). No statistical difference in overall survival at 1 year was found (overall OR, 1.20; 95% CI, 0.63-2.29). Inaccessibility to individual data and time-to-event data and differences in evaluation criteria between studies could have introduced bias. Conclusions and Relevance Dasatinib, nilotinib, and ponatinib increase vascular occlusive events. New-generation TKIs improve MMR but not the overall survival at 1 year in patients with CML.

Non-VKA Oral Anticoagulants: Accurate Measurement of Plasma Drug Concentrations

Non-VKA oral anticoagulants (NOACs) have now widely reached the lucrative market of anticoagulation. While the marketing authorization holders claimed that no routine monitoring is required and that these compounds can be given at fixed doses, several evidences arisen from the literature tend to demonstrate the opposite. New data suggests that an assessment of the response at the individual level could improve the benefit-risk ratio of at least dabigatran. Information regarding the association of rivaroxaban and apixaban exposure and the bleeding risk is available in the drug approval package on the FDA website. These reviews suggest that accumulation of these compounds increases the risk of experiencing a bleeding complication. Therefore, in certain patient populations such as patients with acute or chronic renal impairment or with multiple drug interactions, measurement of drug exposure may be useful to ensure an optimal treatment response. More specific circumstances such as patients experiencing a haemorrhagic or thromboembolic event during the treatment duration, patients who require urgent surgery or an invasive procedure, or patient with a suspected overdose could benefit from such a measurement. This paper aims at providing guidance on how to best estimate the intensity of anticoagulation using laboratory assays in daily practice.