Pathology consultation on anticoagulation monitoring: factor X-related assays

Dose Reduction of Edoxaban in Patients 80 Years and Older With Atrial Fibrillation: Post Hoc Analysis of the ENGAGE AF-TIMI 48 Randomized Clinical Trial

Importance

In older patients with atrial fibrillation who take anticoagulants for stroke prevention, bleeding is increased compared with younger patients, thus, clinicians frequently prescribe lower than recommended doses in older patients despite limited randomized data.

Objective

To evaluate ischemic and bleeding outcomes in patients 80 years and older with atrial fibrillation receiving edoxaban, 60 mg vs 30 mg, and edoxaban, 30 mg vs warfarin.

Design, Setting, and Participants

The ENGAGE AF-TIMI 48 trial (Effective Anticoagulation With Factor Xa Next Generation in Atrial Fibrillation-Thrombolysis in Myocardial Infarction 48) was a parallel-design, double-blind, global clinical trial that randomized patients with atrial fibrillation to either one of 2 edoxaban dosing regimens or warfarin. This secondary analysis focused on patients 80 years or older without dose-reduction criteria receiving edoxaban, 60 mg vs 30 mg, as well as patients with or without dose-reduction criteria receiving edoxaban, 30 mg, vs warfarin. Study data were analyzed between October 2022 and December 2023.

Interventions

Oral edoxaban, 30 mg once daily; edoxaban, 60 mg once daily; or warfarin.

Main Outcomes and Measures

Primary net clinical outcome of death, stroke or systemic embolism, and major bleeding and each individual component.

Results

The current analysis included 2966 patients 80 years and older (mean [SD] age, 83 [2.7] years; 1671 male [56%]). Among 1138 patients 80 years and older without dose-reduction criteria, those receiving edoxaban, 60 mg vs 30 mg, had more major bleeding events (hazard ratio [HR], 1.57; 95% CI, 1.04-2.38; P = .03), particularly gastrointestinal hemorrhage (HR, 2.24; 95% CI, 1.29-3.90; P = .004), with no significant difference in efficacy end points. Findings were supported by analyses of endogenous factor Xa inhibition, a marker of anticoagulant effect, which was comparable between younger patients receiving edoxaban, 60 mg, and older patients receiving edoxaban, 30 mg. In 2406 patients 80 years and older with or without dose-reduction criteria, patients receiving edoxaban, 30 mg, vs warfarin had lower rates of the primary net clinical outcome (HR, 0.78; 95% CI, 0.68-0.91; P = .001), major bleeding (HR, 0.59; 95% CI, 0.45-0.77; P < .001), and death (HR, 0.83; 95% CI, 0.70-1.00; P = .046), whereas rates of stroke or systemic embolism were comparable.

Conclusions and Relevance

In this post hoc analysis of the ENGAGE AF-TIMI 48 randomized clinical trial, in patients 80 years and older with atrial fibrillation, major bleeding events were lower in patients randomized to receive edoxaban, 30 mg per day, compared with either edoxaban, 60 mg per day (in patients without dose-reduction criteria), or warfarin (irrespective of dose-reduction status), without an offsetting increase in ischemic events. These data support the concept that lower-dose anticoagulants, such as edoxaban, 30 mg, may be considered in older patients with atrial fibrillation even in the absence of dose-reduction criteria.

Trial Registration

ClinicalTrials.gov Identifier: NCT00781391.

The Choice between Plasma-Based Common Coagulation Tests and Cell-Based Viscoelastic Tests in Monitoring Hemostatic Competence: Not an either-or Proposition

There has been a significant interest in the last decade in the use of viscoelastic tests (VETs) to determine the hemostatic competence of bleeding patients. Previously, common coagulation tests (CCTs) such as the prothrombin time (PT) and partial thromboplastin time (PTT) were used to assist in the guidance of blood component and hemostatic adjunctive therapy for these patients. However, the experience of decades of VET use in liver failure with transplantation, cardiac surgery, and trauma has now spread to obstetrical hemorrhage and congenital and acquired coagulopathies. Since CCTs measure only 5 to 10% of the lifespan of a clot, these assays have been found to be of limited use for acute surgical and medical conditions, whereby rapid results are required. However, there are medical indications for the PT/PTT that cannot be supplanted by VETs. Therefore, the choice of whether to use a CCT or a VET to guide blood component therapy or hemostatic adjunctive therapy may often require consideration of both methodologies. In this review, we provide examples of the relative indications for CCTs and VETs in monitoring hemostatic competence of bleeding patients.

Assessment of anti-factor Xa activity in critically ill COVID-19 patients receiving three different anticoagulation regimens

INTRODUCTION

Critically ill COVID-19 patients are at increased risk of thrombosis with an enhanced risk of bleeding. We aimed to explore the role of anti-factor Xa levels in optimizing the high-intensity anticoagulation's safety and efficacy and finding possible associations between D-dimer levels, cytokine storm markers, and COVID-19-induced coagulopathy or thrombophilia.

METHODS

Retrospective cohort study conducted on 69 critically ill COVID-19 patients who received three regimens of higher intensity anticoagulation.

RESULTS

Seventeen patients (24.6%) received high-dose enoxaparin prophylaxis, 29 patients (42%) received therapeutic doses of enoxaparin, and 23 patients (33.3%) were on therapeutic unfractionated heparin infusion. Fewer than one-third of the whole cohort (n = 22; 31.8%) achieved the target range of anti-factor Xa. The patients were divided into three subgroups based on anti-factor Xa target status within each anticoagulation regimen; when compared, the only association observed among them was for interleukin-6 levels, which were significantly higher in both the "above the expected range" and "below the expected range" groups compared with the "within the expected range" group (p = 0.009). Major bleeding episodes occurred in 14 (20.3%) patients and were non-significantly more frequent in the "below the expected anti-factor Xa range group" (p = 0.415). Seven patients (10.1%) developed thrombosis. The majority of patients had anti-factor Xa levels below the expected ranges (four patients, 57.1%).

CONCLUSION

Conventional anti-factor Xa ranges may not be appropriate as a predictive surrogate for bleeding in critically ill COVID-19. The clinical decision to initiate therapeutic anticoagulation preemptively may be individualized according to thrombosis and bleeding risks. Cytokine storm markers, namely, interleukin-6, may play a role in COVID-19-induced coagulopathy or thrombophilia.

Anticoagulation Monitoring for Perioperative Physicians

From preoperative medications to intraoperative needs to postoperative thromboprophylaxis, anticoagulants are encountered throughout the perioperative period. This review focuses on coagulation testing clinicians utilize to monitor the effects of these medications.

Assessment of anti-factor Xa activity in critically ill COVID-19 patients receiving three different anticoagulation regimens

Introduction:

Critically ill COVID-19 patients are at increased risk of thrombosis with an enhanced risk of bleeding. We aimed to explore the role of anti-factor Xa levels in optimizing the high-intensity anticoagulation’s safety and efficacy and finding possible associations between D-dimer levels, cytokine storm markers, and COVID-19-induced coagulopathy or thrombophilia.

Methods:

Retrospective cohort study conducted on 69 critically ill COVID-19 patients who received three regimens of higher intensity anticoagulation.

Results:

Seventeen patients (24.6%) received high-dose enoxaparin prophylaxis, 29 patients (42%) received therapeutic doses of enoxaparin, and 23 patients (33.3%) were on therapeutic unfractionated heparin infusion. Fewer than one-third of the whole cohort ( n = 22; 31.8%) achieved the target range of anti-factor Xa. The patients were divided into three subgroups based on anti-factor Xa target status within each anticoagulation regimen; when compared, the only association observed among them was for interleukin-6 levels, which were significantly higher in both the “above the expected range” and “below the expected range” groups compared with the “within the expected range” group ( p = 0.009). Major bleeding episodes occurred in 14 (20.3%) patients and were non-significantly more frequent in the “below the expected anti-factor Xa range group” ( p = 0.415). Seven patients (10.1%) developed thrombosis. The majority of patients had anti-factor Xa levels below the expected ranges (four patients, 57.1%).

Conclusion:

Conventional anti-factor Xa ranges may not be appropriate as a predictive surrogate for bleeding in critically ill COVID-19. The clinical decision to initiate therapeutic anticoagulation preemptively may be individualized according to thrombosis and bleeding risks. Cytokine storm markers, namely, interleukin-6, may play a role in COVID-19-induced coagulopathy or thrombophilia.

Traditional and non-traditional anticoagulation management during extracorporeal membrane oxygenation

Unfractionated heparin (UFH) is the anticoagulant of choice during extracorporeal membrane oxygenation (ECMO) support. Despite its favorable pharmacologic properties, management of heparin anticoagulation during ECMO remains a major challenge. To date, little is known about the optimal monitoring strategy or the heparin dose offering the best safety/efficacy profile. Therefore, it remains unclear if the heparin dose should be adapted to target a specific "clotting time" [e.g., activated clotting time (ACT) or activated partial thromboplastin time (aPTT)] or a heparin concentration, measured by coagulation factor anti-Xa assay. In addition, no study has compared the relevance of modern viscoelastic coagulation tests over the single value of a clotting time or heparin concentration value. Although guidelines for anticoagulation during ECMO support have been published, the absence of evidence limits the quality of the recommendations provided, which explains the major intra- and inter-institutional variability observed. Large prospective multicenter trials are urgently needed to investigate the optimal anticoagulation management strategy during ECMO support.

Differential Assessment of Factor Xa Activity and Global Blood Coagulability Utilizing Novel Dielectric Coagulometry

An easy-to-use assessment for activated factor X (FXa) is lacking despite its pivotal role in the coagulation. Dielectric blood coagulometry (DBCM) was recently invented as a novel assessment tool for determining the whole blood coagulability by measuring the temporal change in the permittivity of blood. We previously reported that it could evaluate the global blood coagulability. This study aimed to apply the DBCM for assessing FXa activity and its inhibition by anticoagulants. We performed the DBCM analysis along with measurement of the FXa activity by a fluorometric assay in samples from healthy subjects, and identified a new index named maximum acceleration time (MAT) that had a correlation to the FXa activity. Next the DBCM analysis was performed using blood samples mixed with anticoagulants (unfractionated heparin, dalteparin, and edoxaban). Blood samples with three anticoagulants had different profiles of the temporal change in the permittivity, reflecting their different selectivity for FXa. We compared the MAT with the anti-FXa activity assay, and found that the prolongation of MAT was similarly correlated with the anti-FXa activity regardless of the type of anticoagulants. In conclusion, the DBCM has the possibility for evaluating the innate FXa activity and effect of anticoagulants focusing on their FXa inhibition.

Clinical Feasibility of Monitoring Enoxaparin Anti-Xa Concentrations: Are We Getting It Right?

Background: Anti-Xa monitoring is utilized to measure the extent of anticoagulation in certain patient populations receiving enoxaparin. It is essential to accurately obtain this pharmacodynamic marker for safe and effective anticoagulation management. Objectives: To determine the frequency of correctly drawn anti-Xa concentrations in accordance with predefined institutional criteria and to determine the number of dose adjustments implemented based on incorrectly drawn anti-Xa concentrations. Methods: This was a retrospective, single-center, cohort study among adult patients who received treatment doses of enoxaparin with measured anti-Xa concentrations. Patients were excluded if they were pregnant, on hemodialysis, or received prophylactic dosing. Anti-Xa levels were defined as correctly measured if they were drawn 3 to 5 hours after the dose during steady state concentrations. Descriptive statistics were performed and analyzed via SPSS software. Results: Overall, 203 patients were reviewed and 59 patients with 74 anti-Xa levels were included. The majority of anti-Xa levels (57/74; 77%) were drawn incorrectly and often resulted in collection of repeat anti-Xa samples. There were 12 documented dose adjustments and approximately 42% (5/12) were based on incorrectly drawn anti-Xa levels. Anti-Xa levels were within target range approximately 45% of the time. Conclusions: Enoxaparin anti-Xa concentrations are frequently drawn incorrectly and dose adjustments are often performed based on these unsupported anti-Xa levels. This may present a potential risk to compromise patient safety.

Heparin-resistant Thrombosis Due to Homozygous Antithrombin Deficiency Treated With Rivaroxaban: A Case Report

BACKGROUND

Heparin fulfills its anticoagulant action through activation of antithrombin (AT), and thus thrombosis secondary to AT deficiency can be associated with heparin resistance.

OBSERVATION

A 12-year-old girl with severe venous thrombosis was referred to us because of undetectable anti-Xa levels despite low-molecular-weight heparin therapy. Laboratory investigations revealed a homozygous AT mutation in the heparin binding site (AT Budapest III). She was subsequently treated with rivaroxaban successfully.

CONCLUSIONS

Heparin resistance warrants evaluation for AT deficiency. Rivaroxaban may be considered a valid anticoagulant alternative to low-molecular-weight heparin in these patients.

Assessment of anti-factor Xa activity of heparin in binary parenteral nutrition admixtures for premature neonates

An in vitro study was carried out to determine the anti-Xa activity of heparin in binary parenteral nutrition (BPN) admixtures for premature neonates in our neonatal intensive care unit (NICU) after a 24-hour infusion, as well as to assess drug interaction with a 50% glucose solution. Two types of bags were prepared: (1) BPN admixtures (composition defined in the NICU) including sodium heparin at 77 UI/mL and (2) bags containing only G50% with sodium heparin at 193 UI/mL. The anti-Xa activity of heparin was measured in bags at T0, after the 24-hour infusion and in eluates at the outlet of the infusion line after 24hours, using a validated chromogenic anti-Xa method. Comparisons of the mean concentration observed with the theoretical value for anti-Xa activity were performed with the Student t-test. Mean values of anti-Xa activity do not differ significantly from the values expected for all conditions. We found a slight variation in anti-Xa activity when infused over 24hours for both types of bags, with and without in-line filtration, showing that heparin remains stable during this infusion period in both BPN admixtures and G50%.

Anticoagulation management associated with extracorporeal circulation

The use of extracorporeal circulation requires anticoagulation to maintain blood fluidity throughout the circuit, and to prevent thrombotic complications. Additionally, adequate suppression of hemostatic activation avoids the unnecessary consumption of coagulation factors caused by the contact of blood with foreign surfaces. Cardiopulmonary bypass represents the greatest challenge in this regard, necessitating profound levels of anticoagulation during its conduct, but also quick, efficient reversal of this state once the surgical procedure is completed. Although extracorporeal circulation has been around for more than half a century, many questions remain regarding how to best achieve anticoagulation for it. Although unfractionated heparin is the predominant agent used for cardiopulmonary bypass, the amount required and how best to monitor its effects are still unresolved. This review discusses the use of heparin, novel anticoagulants, and the monitoring of anticoagulation during the conduct of cardiopulmonary bypass.

Effects of factor VIII levels on the APTT and anti-Xa activity under a therapeutic dose of heparin

In pregnant women, activated partial thromboplastin time (APTT) does not precisely reflect the anticoagulant effect of a therapeutic dose of heparin. However, the measurement of anti-Xa activity can be used to monitor the anticoagulant effect of heparin, since the plasma concentrations of coagulation factors increase in pregnant women. We evaluated the in vitro effects of increased concentrations of fibrinogen and other coagulation factors (FVII, FVIII, and FIX) on the results of assays of APTT and anti-Xa activity in plasma samples with various therapeutic concentrations of unfractionated heparin (UFH). In the presence of UFH, APTT was shortened by increased concentrations of fibrinogen, FVII, or FVIII, and this effect was much stronger when the FVIII concentration was increased. In the plasma samples containing 0.5 or 0.7 U/mL of UFH, the APTT was shortened by approximately half or one-third, respectively, when 6 U FVIII/mL was added to the sample. The anti-Xa activity was not influenced by increased concentrations of the coagulation factors. In the present study, we also evaluated the sensitivities to UHF of four APTT reagents, and found a 1.65-fold difference in the sensitivity to UFH among APTT reagents. Our results demonstrate that increased FVIII concentration shortens APTT under therapeutic doses of UFH, and that APTT thus underestimates the anticoagulant effect of UFH in pregnant women, mainly due to the increased FVIII concentration.