Laboratory determination of old and new targeted anticoagulant agents for prevention of bleeding and thrombotic events in cancer patients

Slightly elevated international normalized ratio predicts bleeding episodes in patients treated with direct oral anticoagulants

Introduction

Patients treated with direct oral anticoagulants (DOACs) are at increased bleeding risk. It is therefore of increasing interest to identify predictors of bleeding episodes to increase safety during treatment with DOACs.

Methods

This retrospective cohort study systematically reviewed medical records of 235 patients treated with either apixaban, rivaroxaban or dabigatran for non-valvular atrial fibrillation or venous thromboembolism and collected data on the international normalized ratio (INR) and all bleeding episodes.

Results

INR ≥ 1.5 was significantly associated with increased risk of minor and major bleeding events in patients treated with direct factor Xa inhibitors. This association was not present in patients treated with dabigatran. However, a high negative predictive value was identified for INR < 1.5 for all drugs. The relative risks of bleeding episodes in patients with INR ≥ 1.5 and INR < 1.5 were 5.1 and 0.20, respectively.

Conclusions

Our results demonstrate a strong correlation between INR and risk of bleeding episodes during DOAC treatment. INR < 1.5 was a strong negative predictor for low bleeding risk independent of indication or choice of drug, and INR ≥ 1.5 was associated with increased risk of bleeding episodes in patients treated with direct factor Xa-inhibitors.

[Venous thromboembolic complications in oncological patients: present-day possibilities of effective and safe anticoagulant therapy]

Cancer-associated thromboembolic complications in malignant neoplasms are commonly encountered. They deteriorate the course of the underlying disease and are frequent causes of death. The oncological patient is at high risk of not only thrombosis but haemorrhage during anticoagulant therapy. Recent randomized clinical trials have positively appreciated the possibilities of direct oral anticoagulants in treatment and prevention of thromboses in oncological patients. Analysing subgroups in these studies demonstrated that direct oral anticoagulants during long-term administration were at least as effective and safe as vitamin K antagonists. The most significant by the number of cases, duration of therapy, and methodology of analysis are the reports regarding rivaroxaban - an oral, direct factor Xa inhibitor. There are also findings obtained in a separate randomized study, confirming efficacy and safety of rivaroxaban in treatment of patients with cancer-associated venous thromboembolic complications as compared with therapy with low-molecular-weight heparins. Namely these results formed the basis for the guidelines of the International Society on Thrombosis and Hemostasis (SSC ISTH), according to which rivaroxaban may be regarded as an alternative to low-molecular-weight heparins in certain clinical situations.

In vitro and ex vivo Measurement of Prophylactic Dabigatran Concentrations with a New Ecarin-Based Thromboelastometry Test

BACKGROUND

An increasing number of oral anticoagulants has been approved, including dabigatran etexilate (DE). DE is a direct thrombin inhibitor that requires no routine monitoring, but, if necessary (e.g. urgent surgery etc.), the diluted thrombin time measured with Hemoclot® has shown reliable results. So far, no point-of-care (PoC) assay is available to measure DE effects. The EcaTEM assay uses ecarin to initiate the coagulation cascade at the step of thrombin generation and measures the clotting time (CT) by thromboelastometry.

METHODS

This study investigated the correlation of the EcaTEM with standard laboratory assays in dabigatran-treated patients. Ten patients undergoing total hip or knee arthroplasty were included in the study. DE for thromboprophylaxis was started 4 h after surgery. Blood samples were taken before surgery as well as 2, 6 and 12 h after ingestion on the 3rd postoperative day. Dabigatran concentration (Hemoclot), activated partial thromboplastin time, thrombin time and CT EcaTEM were measured.

RESULTS

Only CT EcaTEM and Hemoclot showed a correlation > 0.75 for all measurements.

CONCLUSION

CT EcaTEM appears a valid PoC method parameter to detect thrombin inhibition and thus the presence of dabigatran beside diluted thrombin time at different concentration levels. This may represent an opportunity to identify the presence of dabigatran, e.g., in emergency situations.