From Vitamin K Antagonists to Liver International Normalized Ratio: A Historical Journey and Critical Perspective

Direct oral anticoagulants in cirrhosis: Rationale and current evidence

Cirrhosis is a major health concern worldwide with a complex pathophysiology affecting various biological systems, including all aspects of haemostasis. Bleeding risk is mainly driven by portal hypertension, but in end-stage liver disease it is further increased by alterations in haemostatic components, including platelet function, coagulation, and fibrinolysis. Concurrently, patients with cirrhosis are prone to venous thromboembolic events (VTE) because of the altered haemostatic balance, in particular an increase in thrombin generation. In patients with cirrhosis, vitamin K antagonists (VKA) and low molecular weight heparins (LMWH) are currently the standard of care for VTE prevention, with VKA also being standard of care for stroke prevention in those with atrial fibrillation. However, direct oral anticoagulants (DOAC) could have specific advantages in this patient population. Clinical experience suggests that DOAC are a safe and possibly more effective alternative to traditional anticoagulants for the treatment of VTE in patients with compensated cirrhosis. In addition, emerging data suggest that primary prophylactic treatment with anticoagulants may improve clinical outcomes in patients with cirrhosis by reducing the risk of hepatic decompensation. The selection of the most appropriate DOAC remains to be clarified. This review focuses on the rationale for the use of DOAC in patients with cirrhosis, the specific effects of the different DOAC (as assessed by in vitro and in vivo pharmacokinetic and pharmacodynamic studies), as well as clinical outcomes in patients with cirrhosis on DOAC.

Continued harmonization of the international normalized ratio across a large laboratory network: Evidence of sustained low interlaboratory variation and bias after a change in instrumentation

OBJECTIVES

Our objective was to maintain low interlaboratory variation and bias in international normalized ratio (INR) results following a network change in instrumentation and reagents, using a process of ongoing standardization and harmonization.

METHODS

Network-wide standardization to new common instrument and reagent platforms followed by network-wide application of a simple novel process of verification of international sensitive index and mean normal prothrombin time values for each new lot of prothrombin time (PT) reagent that does not require use of World Health Organization reference thromboplastin or INR calibration/certified plasma.

RESULTS

The network transitioned from mechanical hemostasis detection instruments with associated PT reagent (Diagnostica Stago; NeoPTimal) to optical detection (ACL TOPs) with associated PT reagent (Werfen; RecombiPlasTin 2G). Comparing 3 years of data for each situation, the network (n = 27 laboratories) maintained low INR variability and bias relative to general mechanical and optical groups and other laboratories.

CONCLUSIONS

Harmonized support for patient management of vitamin K antagonists such as warfarin was continuously maintained in our geography, with potentially positive implications for other coagulation laboratories and geographies. For the United States in particular, paucity of US Food and Drug Administration-cleared INR certified plasmas potentially compromises INR test accuracy; our novel approach may provide workable alternatives for other laboratories/networks.

A Brief History of Hemostasis and Thrombosis at the Mayo Clinic

Coagulation is a crucial biological mechanism in human bodies to prevent blood loss. Abnormal coagulation can cause bleeding diathesis or thrombosis, common pathologic conditions in our clinical practice. Many individuals and organizations have dedicated their efforts in the past decades to understanding the biological and pathological mechanisms of coagulation and developing laboratory testing tools and treatment options to help patients with bleeding or thrombotic conditions. Since 1926, the Mayo Clinic coagulation group has made significant contributions to the clinical and laboratory practice, basic and translational research on various hemostatic and thrombotic disorders, and the education and collaboration to share and advance our knowledge in coagulation through a highly integrated team and practice model. We would like to use this review to share our history and inspire medical professionals and trainees to join the efforts to advance our understanding of coagulation pathophysiology and improve our care for patients with coagulation disorders.

Anticoagulant therapy for splanchnic vein thrombosis: recent updates for patients with liver cirrhosis

INTRODUCTION

Liver cirrhosis is accompanied by several hemostatic alterations, which contribute to the current theory of "rebalanced hemostasis." Splanchnic vein thrombosis (SVT) is a frequent complication of liver cirrhosis (17-26% of the cirrhotic patients), and liver cirrhosis is a common risk factor for SVT (24-28% of SVT cases).

AREAS COVERED

This narrative review aims to describe the current state of the art on the anticoagulant treatment of cirrhotic SVT, with a particular focus on the possible role of the direct oral anticoagulants (DOACs) and recent guidelines on this topic.

EXPERT OPINION

Early anticoagulant therapy is recommended in cirrhotic patients with acute SVT, to obtain vessel recanalization and decrease the rates of portal hypertension-related complications. Gastroesophageal varices do not represent a contraindication to anticoagulation, if adequate prophylaxis of variceal bleeding is established, and varices band ligation can be safely performed without the need to stop the anticoagulant treatment. The conventional treatment of cirrhotic SVT consisted of low molecular weight heparin, as initial treatment of choice, eventually followed by vitamin K antagonists, but the DOACs can be considered as a reasonable alternative in patients with compensated liver cirrhosis.

The Mortality Index for Alcohol-Associated Hepatitis: A Novel Prognostic Score

OBJECTIVE

To develop a new scoring system that more accurately predicts 30-day mortality in patients with alcohol-associated hepatitis (AH).

METHODS

A cohort of consecutive adults diagnosed with AH at a single academic center from January 1, 1998, to December 31, 2018, was identified for model derivation. Multivariate logistic regression was used to create a new scoring system to predict 30-day mortality. External validation of this score was performed on a multicenter retrospective cohort.

RESULTS

In the derivation cohort of 266 patients, the 30-day mortality rate was 19.2%. The following variables were found to be significantly associated with mortality on multivariate analysis: age (P=.002), blood urea nitrogen (P=.003), albumin (P=.01), bilirubin (P=.02), and international normalized ratio (P=.001). A model incorporating these variables, entitled the Mortality Index for Alcohol-Associated Hepatitis (MIAAH), achieved a C statistic of 0.86. Comparison of the accuracy of the MIAAH to existing prognostic models, including the Model for End-Stage Liver Disease and Maddrey Discriminant Function, showed that the highest concordance was achieved by the MIAAH and that this difference was significant. In the validation cohort of 249 patients, the MIAAH C statistic decreased to 0.73 and was found to be significantly superior to the Maddrey Discriminant Function but not to the Model for End-Stage Liver Disease.

CONCLUSION

The MIAAH competes with the current prognostication models and is at a minimum as accurate as these existing scores in identifying patients with AH at high risk of short-term mortality. Furthermore, the MIAAH demonstrates advantageous performance characteristics in its ability to increasingly accurately dichotomize patients into those at highest risk of death and those likely to survive.

Hemostatic Testing in Critically Ill Infants and Children

Children with critical illness frequently manifest imbalances in hemostasis with risk of consequent bleeding or pathologic thrombosis. Traditionally, plasma-based tests measuring clot formation by time to fibrin clot generation have been the "gold standard" in hemostasis testing. However, these tests are not sensitive to abnormalities in fibrinolysis or in conditions of enhanced clot formation that may lead to thrombosis. Additionally, they do not measure the critical roles played by platelets and endothelial cells. An added factor in the evaluation of these plasma-based tests is that in infants and young children plasma levels of many procoagulant and anticoagulant proteins are lower than in older children and adults resulting in prolonged clot generation times in spite of maintaining a normal hemostatic "balance." Consequently, newer assays directly measuring thrombin generation in plasma and others assessing the stages hemostasis including clot initiation, propagation, and fibrinolysis in whole blood by viscoelastic methods are now available and may allow for a global measurement of the hemostatic system. In this manuscript, we will review the processes by which clots are formed and by which hemostasis is regulated, and the rationale and limitations for the more commonly utilized tests. We will also discuss selected newer tests available for the assessment of hemostasis, their "pros" and "cons," and how they compare to the traditional tests of coagulation in the assessment and management of critically ill children.

Safety of direct-acting oral anticoagulants relative to warfarin in a matched cohort of liver transplant recipients

Despite increasingly widespread utilization of direct-acting oral anticoagulants (DOACs), there remains limited experience with the use of these agents following liver transplantation. We performed a single-center, retrospective review of liver transplant recipients prescribed DOACs or warfarin between January 2014 and January 2018. Patients receiving DOACs were matched with warfarin-treated controls based on discrete clinical parameters and followed from the time of anticoagulant prescription, until treatment discontinuation or study conclusion. The primary endpoint for this review was the incidence of clinically relevant major or non-major bleeding among the treatment groups. Twenty-seven patients prescribed DOACs were identified for inclusion in the review, of which 20 could be matched with suitable warfarin controls. At the conclusion of the study, warfarin-treated patients had a significantly higher incidence of clinically relevant bleeding (45% vs 15%; P = .01). No statistically significant differences were found in the rate of new or recurrent thrombotic events. Multivariable logistic regression demonstrated that warfarin treatment was associated with a significantly higher odds of a bleeding event compared to treatment with a DOAC (OR = 6.9; 95% CI, 1.1-44.6). DOAC use appears relatively safe compared with warfarin in select liver transplant recipients. Patient-specific factors still bear consideration when selecting between the various anticoagulant options.

Cholesterol esterification in plasma as a biomarker for liver function and prediction of mortality

Background

Advanced stages of liver cirrhosis lead to a dramatically increased mortality. For valid identification of these patients suitable biomarkers are essential. The most important biomarkers for liver function are bilirubin and prothrombin time expressed as International Normalized Ratio (INR). However, the influence of several anticoagulants on the prothrombin time limits its diagnostic value.

Aim of this study was the evaluation of cholesterol esterification (CE) fraction (esterified cholesterol vs. total cholesterol) as an alternative biomarker for liver synthesis and mortality prediction. Under physiological conditions the CE fraction in blood is closely regulated by lecithin-cholesterol acyltransferase (LCAT) which is produced in the liver.

Methods

One hundred forty-two patients with liver disease clinically considered for orthotopic liver transplant for different indications were enrolled in the study. One patient was excluded because of the intake of a direct oral factor Xa inhibitor which has a strong impact on prothrombin time.

Results

Results of CE fraction were in good agreement with INR (R² = 0.73; p < 0.001). In patients who died or survived within three months mean CE fraction was 56% vs. 74% (p < 0.001) and mean INR was 2.0 vs. 1.3 (p < 0.001), respectively. The predictive value of CE fraction for three-month mortality risk was higher compared to INR (p = 0.04). Results for one-year mortality were comparable.

Conclusions

The cholesterol esterification fraction is a valid biomarker for liver synthesis and allows reliable prediction of mortality. In contrast to INR, it is independent of anticoagulation and other analytical limitations of coagulation tests.

Electronic supplementary material

The online version of this article (doi:10.1186/s12876-017-0614-9) contains supplementary material, which is available to authorized users.

Impact of coagulation function and anticoagulation therapy on liver fibrosis

Liver cirrhosis and its complications, including esophageal and gastric variceal bleeding, hepatic encephalopathy, and ascites, can cause serious harm to human health. Therefore, treatment of liver fibrosis is key to the prevention and treatment of liver cirrhosis. In order to treat liver fibrosis to reduce human suffering, medical experts and scholars have performed many clinical and animal studies to find safe, efficient and reliable drugs to slow the progression of hepatic fibrosis and even reverse the liver function. This review introduces the definition of liver fibrosis in China and other countries, discusses the effect of coagulation on the process of liver fibrosis and various anticoagulation therapies for liver fibrosis, and summarizes the advantages, disadvantages, and side effects of different anticoagulants in the prevention and treatment of liver fibrosis.

Point of Care Assessment of Coagulation

Disorders of hemostasis can be difficult to fully elucidate but can severely affect patient outcome. The optimal therapy for coagulopathies is also not always clear. Point of care (POC) testing in veterinary medicine can assist in the diagnosis of hemostatic disorders and also direct treatment. Advantages of POC testing include rapid turnaround times, ease of use, and proximity to the patient. Disadvantages include differences in analytic performance compared with reference laboratory devices, the potential for operator error, and limited test options per device. Conventional coagulation tests such as prothrombin time, activated partial thromboplastin time, and activated clotting time can be measured by POC devices and can accurately diagnose hypocoagulability, but they cannot detect hypercoagulability or disorders of fibrinolysis. Viscoelastic POC coagulation testing more accurately evaluates in vivo coagulation, and can detect hypocoagulability, hypercoagulability, and alterations in fibrinolysis. POC platelet function testing methodologies can detect platelet adhesion abnormalities including von Willebrand disease, and can be used to monitor the efficacy of antiplatelet drugs. It is unlikely that a single test would be ideal for assessing the complete coagulation status of all patients; therefore, the ideal combination of tests for a specific patient needs to be determined based on an understanding of the underlying disease, and protocols must be standardized to minimize interoperator and interinstitutional variability.

Harmonizing the International Normalized Ratio (INR) : Standardization of Methods and Use of Novel Strategies to Reduce Interlaboratory Variation and Bias

OBJECTIVES

To reduce interlaboratory variation and bias in international normalized ratio (INR) results, as used to monitor patients receiving vitamin K antagonist therapy, including warfarin, in a large pathology network (n = 27 laboratories) by procedural standardization and harmonization.

METHODS

Network consensus to standardize to common instrument and reagent platforms was established, following development of hemostasis test specifications. Subsequent installations and implementation occurred after conclusion of a government tender process. Network-wide application of simple novel process of verification harmonization of local international sensitive index and mean normal prothrombin time initiated for each new lot of INR reagent that does not require ongoing use of reference thromboplastin or calibration/certified plasma sets.

RESULTS

We achieved reduction of different instrument manufacturers (from four to one), instrument types (10 to three), reagent types (four to one), and instrument/reagent combinations (12 to three), plus substantial reduction in INR variability and bias.

CONCLUSIONS

Results infer significant improvement in local patient management, with positive implications for other laboratories. For the United States in particular, lack of US Food and Drug Administration-cleared certified plasmas may compromise INR accuracy, and our novel approach may provide a workable alternative for laboratories and networks.