Development and validation of an ultra-high performance liquid chromatography with tandem mass spectrometry method for the simultaneous quantification of direct oral anticoagulants in human plasma

Direct oral anticoagulants are widely used to treat and prevent thromboembolic disorders. With rising clinical application, monitoring concentrations of direct oral anticoagulants are necessary in certain clinical conditions. A rapid and sensitive ultra-performance liquid chromatography-tandem mass spectrometry method was developed for the simultaneous determination of dabigatran etexilate, dabigatran, rivaroxaban, edoxaban, and apixaban, in human plasma. Protein precipitation with methanol was performed for sample preparation. The direct oral anticoagulants and internal standards were separated under gradient conditions using a C18 column, at an analytical run time of 8 min. The mobile phase was composed of 0.1% (v/v) formic acid in water (solvent A) and 0.1% (v/v) formic acid in acetonitrile (solvent B) at a flow rate of 0.3 mL/min. Mass detection was performed in multiple reaction monitoring using positive ionization mode. The method was validated over a range of 1.0-500 ng/mL for dabigatran etexilate, 0.1-500 ng/mL for dabigatran, and 0.5-500 ng/mL for edoxaban, rivaroxaban, and apixaban. The method detection limits of five analytes were in the range of 0.05-0.5 ng/mL. The lower limits of quantification of five analytes ranged from 0.1 to 1 ng/mL. The linearity (r² values) was higher than 0.997. The accuracy of the low, medium, and high quality control samples were between 85.9 and 114%, and intra- and inter-day precision were below 9.47%. This validated method was successfully used to determine the plasma concentrations of rivaroxaban in 32 patients, and of dabigatran etexilate and dabigatran in 1 patient.

Dose reduction of edoxaban preserves efficacy and safety for the treatment of venous thromboembolism

Direct oral anticoagulants simplify venous thromboembolism (VTE) treatment by obviating the need for coagulation monitoring. Nonetheless, renal function, body weight and P-glycoprotein inhibitors influence drug levels. The objective of this analysis was to determine whether reduction in edoxaban dose based on clinical criteria avoids excess drug exposure and preserves efficacy and safety in the Hokusai-VTE study. After initial heparin, patients received edoxaban or warfarin for 3-12 months. Edoxaban was given once daily at a dose of 60 mg, which was reduced to 30 mg in patients with a creatinine clearance of 30–50 ml/minute, body weight ≤60 kg or receiving certain P-glycoprotein inhibitors. The primary efficacy outcome was recurrent VTE and the principal safety outcome was major or clinically relevant non-major bleeding. A total of 8292 patients with acute VTE were randomised, 733 and 719 patients in the edoxaban and warfarin groups met the criteria for dose reduction. These patients were older, more often female or Asian and had more extensive VTE. Edoxaban levels were lower in the 30 mg edoxaban group. Rates of recurrent VTE and bleeding with the 30 mg and 60 mg edoxaban dose were comparable: VTE rates were 3.0 % and 3.2 % and clinically relevant bleeding rates were 7.9 % and 8.6 %, respectively. Rates of recurrent VTE and bleeding in the warfarin-treated patients meeting the criteria for dose reduction were 4.2 % and 12.8 %, respectively. The reduced dose edoxaban regimen maintained efficacy and safety compared with the 60 mg dose but was safer than warfarin in patients meeting the criteria for dose reduction.

Supplementary Material to this article is available online at www.thrombosis-online.com.

Accuracy and consistency of anti-Xa activity measurement for determination of rivaroxaban plasma levels

Essentials Accurate determination of anticoagulant plasma concentration is important in clinical practice. We studied the accuracy and consistency of anti-Xa assays for rivaroxaban in a multicentre study. In a range between 50 and 200 μg L-1 , anti-Xa activity correlated well with plasma concentrations. The clinical value might be limited by overestimation and intra- and inter-individual variation.

SUMMARY

Background Determining the plasma level of direct oral anticoagulants reliably is important in the work-up of complex clinical situations. Objectives To study the accuracy and consistency of anti-Xa assays for rivaroxaban plasma concentration in a prospective, multicenter evaluation study employing different reagents and analytical platforms. Methods Rivaroxaban 20 mg was administered once daily to 20 healthy volunteers and blood samples were taken at peak and trough levels (clinicaltrials.gov NCT01710267). Anti-Xa activity was determined in 10 major laboratories using different reagents and analyzers; corresponding rivaroxaban plasma concentrations were measured by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS). Findings Overall Pearson's correlation coefficient of anti-Xa levels and HPLC-MS results was 0.99 for Biophen® Heparin (95% CI, 0.99, 0.99), Biophen® DiXaI (95% CI, 0.99, 0.99) and STA® anti-Xa liquid (95% CI, 0.99, 1.00). Correlation was lower in rivaroxaban concentrations below 50 μg L-1 and above 200 μg L-1 . The overall bias of the Bland-Altman difference plot was 14.7 μg L-1 for Biophen Heparin, 17.9 μg L-1 for Biophen DiXal and 19.0 μg L-1 for STA anti-Xa liquid. Agreement between laboratories was high at peak level but limited at trough level. Conclusions Anti-Xa activity correlated well with rivaroxaban plasma concentrations, especially in a range between 50 and 200 μg L-1 . However, anti-Xa assays systematically overestimated rivaroxaban concentration as compared with HPLC-MS, particularly at higher concentrations. This overestimation, coupled with an apparent interindividual variation, might affect the interpretation of results in some situations.

Direct oral anticoagulants in patients with cervical artery dissection and cerebral venous thrombosis. A case series and review of the literature

BACKGROUND

To date, very little is known about the effects of direct oral anticoagulants (DOA) use in patients with cervical artery dissection (CAD) and cerebral venous thrombosis (CVT). We present our initial experience with the use of DOA for CAD and CVT and an overview of the published literature.

METHODS

From our database, we identified 4 patients who received DOA after CAD and 4 patients after CVT. Also, we analyzed the data reported for 45 patients who received DOA after CAD and 23 after CVT from review of the literature.

RESULTS

Among patients with CAD, resolved or improved arterial stenosis was noted in 27 (55%), and symptomatic recurrent ischemic stroke in 2 (4%). Among patients with CVT, complete or partial recanalization was noted in 25 (90%), and no significant functional disability in 26 (93%). No patient developed intracranial hemorrhage.

CONCLUSIONS

Although no statistical conclusions can be drawn from these data, DOA could be an alternative in patients with CAD-related embolic infarct and CVT-related hemorrhagic venous infarct. A large-scale clinical trial will be needed to validate these results.

Anti-Xa bioassays for the laboratory measurement of direct Factor Xa inhibitors in plasma, in selected patients

In the past decade Direct Oral Anti-Coagulants (DOACs), targeting Thrombin or Factor Xa, have enormously facilitated the daily treatment of all relevant patients, including those requiring lifelong therapy. These DOACs have considerable advantages over the use of oral Vitamin K Antagonist (VKA) treatments, in view of having little interferences with food and other medications and also not requiring adjustment for age, gender or weight, with some well-defined exceptions. In this current What's Happening Section we focus on measurements of DiXaIs in plasma using anti-Xa assays, with the objective of providing a tribute to Professor Michel Meyer Samama, who was not only a real leader in this field but, in the past, both authors benefited from his wisdom, as a teacher who dedicated his scientific and professional life (among many other interests in hemostasis, thrombosis and fibrinolysis) to develop and promote methods and strategies for laboratory monitoring of anticoagulants. This review presents the performance characteristics of the Anti-Factor Xa assays (measuring Factor Xa inhibition by drugs), which are available for measuring Direct Factor Xa Inhibitors in plasma, and show good compliance of the results with the reference LC:MS method (which measures the mass of Direct Factor Xa Inhibitors). We also present the preparation and validation of drug specific plasma calibrators and controls which are requested for drug measurements. These assays are convenient and practical laboratory tools which can be used in any laboratory setting, and meet the requirements of regulatory bodies for making smart, quantitative, sensitive, accurate and ease of use assays for measuring DOACs when needed. The manuscript focuses mainly on the following areas of current interest: interference in coagulation assays; anti-Xa laboratory methods; development of calibrators and controls for DiXaIs; method validation and comparison with reference techniques (LC:MS); regulatory requirements and method registrations; newer clinical applications and experience on DiXaIs with Anti-Xa assays, and future perspectives.

Oral Anticoagulation in the Elderly: New Oral Anticoagulants-Innovative Solution for an Old Problem?

Direct oral anticoagulants emerge as the most innovative and promising drug toward preventing and treating cardiovascular disease, raising great interest among the scientific community. Numerous studies and meta-analysis generated much data clarifying clinicians' doubts; however, uncertainties remain regarding their use in particular groups such as patients with prosthetic valves, in valvular atrial fibrillation (defined as atrial fibrillation related to mitral rheumatic heart disease or prosthetic heart valves), among the elderly, in paraneoplastic thromboembolism, in pulmonary embolism with hemodynamic compromise, and scarcity of specific antidotes. This review article intends to condense the vast scientific production addressing new oral anticoagulants by focusing on their advantages and disadvantages when used on the elderly.

Right ventricular thrombus formation in a patient with arrhythmogenic right ventricular dysplasia following radiofrequency ablation

A middle-aged female suffering from ARVD presented for routine follow-up 8 weeks after right ventricular radiofrequency ablation of recurring ventricular tachycardia. Echocardiography revealed two right ventricular thrombi in the scar area of right ventricular radiofrequency ablation. Ablation-related thromboembolic events should be considered as possible complication in patients suffering from ARVD.

Feasibility and safety of rehabilitation after venous thromboembolism

BACKGROUND

Venous thromboembolism is a life-threatening disease. In survivors, different degrees of functional complaints need to be restored or prevented (eg, post-thrombotic syndrome, pulmonary hypertension). Therefore, rehabilitation after venous thromboembolism is recommended in Germany. However, a structured rehabilitation program has not been defined for this indication. Here, we present the experience of a single rehabilitation center.

METHODS

Data from consecutive pulmonary embolism (PE) patients who were referred for a 3-week inpatient rehabilitation program from 2006 to 2014 were retrospectively evaluated.

RESULTS

In all, 422 patients were identified. The mean age was 63.9±13.5 years, the mean body mass index (BMI) was 30.6±6.2 kg/m2, and 51.9% were female. Deep vein thrombosis according to PE was known for 55.5% of all patients. We applied a wide range of therapeutic interventions such as bicycle training with monitored heart rate in 86.7%, respiratory training in 82.5%, aquatic therapy/swimming in 40.1%, and medical training therapy in 14.9% of all patients. Adverse events (AEs) occurred in 57 patients during the 3-week rehabilitation period. The most common AEs were cold (n=6), diarrhea (n=5), and infection of the upper or lower respiratory tract that was treated with antibiotics (n=5). However, three patients under anticoagulation therapy suffered from bleeding, which was clinically relevant in one. Four patients (0.9%) had to be transferred to a primary care hospital for non-PE-associated reasons (acute coronary syndrome, pharyngeal abscess, and acute abdominal problems). No influence of any of the physical activity interventions on the incidence of any AE was found.

CONCLUSION

Since PE is a life-threatening disease, it seems reasonable to recommend rehabilitation at least in PE patients with an intermediate or high risk. It is shown for the first time in this study that a standard rehabilitation program after PE is safe. However, efficacy and safety in the long term need to be studied prospectively.

Anticoagulant treatment for acute pulmonary embolism: a pathophysiology-based clinical approach

The management of patients with acute pulmonary embolism is made challenging by its wide spectrum of clinical presentation and outcome, which is mainly related to patient haemodynamic status and right ventricular overload. Mechanical embolic obstruction and neurohumorally mediated pulmonary vasoconstriction are responsible for right ventricular overload. The pathophysiology of acute pulmonary embolism is the basis for risk stratification of patients as being at high, intermediate and low risk of adverse outcomes. This risk stratification has been advocated to tailor clinical management according to the severity of pulmonary embolism. Anticoagulation is the mainstay of the treatment of acute pulmonary embolism. New direct oral anticoagulants, which are easier to use than conventional anticoagulants, have been compared with conventional anticoagulation in five randomised clinical trials including >11 000 patients with pulmonary embolism. Patients at high risk of pulmonary embolism (those with haemodynamic compromise) were excluded from these studies. Direct oral anticoagulants have been shown to be as effective and at least as safe as conventional anticoagulation in patients with pulmonary embolism without haemodynamic compromise, who are the majority of patients with this disease. Whether these agents are appropriate for the acute-phase treatment of patients at intermediate-high risk pulmonary embolism (those with both right ventricle dysfunction and injury) regardless of any risk stratification remains undefined.

Timing of discharge follow-up for acute pulmonary embolism: retrospective cohort study

Introduction

Historically, emergency department (ED) patients with pulmonary embolism (PE) have been admitted for several days of inpatient care. Growing evidence suggests that selected ED patients with PE can be safely discharged home after a short length of stay. However, the optimal timing of follow up is unknown. We hypothesized that higher-risk patients with short length of stay (<24 hours from ED registration) would more commonly receive expedited follow up (≤3 days).

Methods

This retrospective cohort study included adults treated for acute PE in six community EDs. We ascertained the PE Severity Index risk class (for 30-day mortality), facility length of stay, the first follow-up clinician encounter, unscheduled return ED visits ≤3 days, 5-day PE-related readmissions, and 30-day all-cause mortality. Stratifying by risk class, we used multivariable analysis to examine age- and sex-adjusted associations between length of stay and expedited follow up.

Results

The mean age of our 175 patients was 63.2 (±16.8) years. Overall, 93.1% (n=163) of our cohort received follow up within one week of discharge. Fifty-six patients (32.0%) were sent home within 24 hours and 100 (57.1%) received expedited follow up, often by telephone (67/100). The short and longer length-of-stay groups were comparable in age and sex, but differed in rates of low-risk status (63% vs 37%; p<0.01) and expedited follow up (70% vs 51%; p=0.03). After adjustment, we found that short length of stay was independently associated with expedited follow up in higher-risk patients (adjusted odds ratio [aOR] 3.5; 95% CI [1.0–11.8]; p=0.04), but not in low-risk patients (aOR 2.2; 95% CI [0.8–5.7]; p=0.11). Adverse outcomes were uncommon (<2%) and were not significantly different between the two length-of-stay groups.

Conclusion

Higher-risk patients with acute PE and short length of stay more commonly received expedited follow up in our community setting than other groups of patients. These practice patterns are associated with low rates of 30-day adverse events.

Dental Procedures in Patients with Atrial Fibrillation and New Oral Anticoagulants

This review discusses the basic pharmacology of new oral anticoagulants that are used for prevention of thromboembolism in patients with atrial fibrillation. It presents available evidence, and provides recommendations for the management of patients requiring invasive procedures in dental practice.