Report of surgeries, their outcome and the thrombin generation assay in patients with Factor XI deficiency: A retrospective single-centre study

Anticoagulant drugs targeting factor XI/XIa and coagulation tests: we urgently need reliable pharmacodynamic data

Antifactor (F)XI/FXIa anticoagulants under development include antisense oligonucleotides, monoclonal antibodies, and small molecules. They do not require routine monitoring, but knowledge of their impact on coagulation tests is essential in view of their expected widespread use. A concentration-dependent prolongation of activated partial thromboplastin time has been shown but varies according to reagents, and the lack of comprehensive data makes interpretation of this test difficult. Measurement of FXI clotting activity is relevant only in case of treatment with antisense oligonucleotides. Measurement of contact pathway factors, if required, should be performed after multiple dilutions of the plasma sample to overcome any inhibitory effect of the anticoagulant. All other tests used in clinical trials (FXIa, FXI antigenic method, and specific thrombin generation assay) are not implemented in clinical laboratories. More comprehensive information on the effect of anti-FXI/FXIa anticoagulants on coagulation tests is urgently needed to anticipate the use of these drugs once they are approved.

Laboratory and Molecular Diagnosis of Factor XI Deficiency

The prevalence of factor XI (FXI) deficiency is 1 per 10 to 20,000 in the general population, much higher than that reported in most texts. The prevalence is higher in Ashkenazi Jews where it is about 1:20. Clinically, FXI deficiency presents as a mild bleeding disorder mostly associated with posttraumatic or postsurgical hemorrhages or unexplained minor bleeding. It is often discovered due to incidental finding of a prolonged activated partial thromboplastin time (aPTT) on routine laboratory screening. FXI deficiency is an autosomal recessive bleeding disorder with many causative F11 gene defects. Diagnosis is based on FXI activity, antigen levels, and molecular diagnostics. As FXI levels do not correlate with bleeding symptoms, identification of pathogenic genetic variants may be a more accurate predictor of bleeding risk and therefore aid in the clinical management of the patient. Two variants in the F11 gene account for most cases found in the Jewish and Arab populations. Patients with FXI deficiency can develop inhibitors to FXI although spontaneously acquired inhibitors are extremely rare. We will discuss laboratory and molecular assays used to diagnose FXI deficiency as well as interferences that can complicate diagnosis including new anticoagulants and acquired FXI inhibitors.

Moderate factor XI deficiency and neuraxial procedures in an obstetric cohort: a retrospective study (2014-2021)

BACKGROUND

Factor XI (FXI) deficiency is a rare inherited bleeding disorder potentially associated with an increased risk of bleeding, particularly in traumatic or surgical situations. The correlation between FXI levels and bleeding risk is weak, leading to ongoing debate regarding the FXI threshold for authorizing neuraxial procedures in obstetric patients. We report data on a cohort of pregnant women with FXI deficiency.

METHODS

This retrospective study included all pregnant women admitted to two high-risk obstetric departments between 2014 and 2021, with FXI levels ≤0.50 IU/mL from the start of pregnancy to postpartum day 1. Data recorded included demographic information, obstetrical history, characteristics of the current pregnancy, personal and familial bleeding history, and biological results.

RESULTS

A total of 101 women (107 deliveries) were included in this analysis, of which 67 delivered with neuraxial labor analgesia or cesarean anesthesia. All but one had a FXI level >0.30 IU/mL, and 9/67 (13%) reported a bleeding history. No hemorrhagic complications related to neuraxial anesthesia were reported.

CONCLUSION

Our findings are consistent with previous reports of positive outcomes after neuraxial procedures in pregnant women with FXI level >0.30 IU/mL, with a thorough review of personal and family bleeding history.

Two cases of Factor XI deficiency: Use of Thrombin Generation Assays (TGA) to detect a non-bleeding phenotype

Factor XI deficiency is a rare disorder of hemostasis. Previously also known as "hemophilia C", this defect has been regarded as a risk factor for bleeding. However, it has been known for long that bleeding tendency and severity of bleeding are not related to the residual factor XI activity in symptomatic patients. Moreover, a large proportion of patients with even severe factor XI deficiency are clinically unremarkable and do not show any signs of abnormal bleeding. Here, we present two cases of factor XI deficiency with a non-bleeding phenotype. Adequate diagnostic work-up and evaluation of the bleeding risk are reported and discussed with focus on thrombin generation assays (TGA) for the prediction of bleeding in affected patients. This is of high relevance in affected patients, particularly in the context of surgery.

Factor XI deficiency: phenotypic age-related considerations and clinical approach towards bleeding risk assessment

ABSTRACT

Factor XI (FXI) deficiency is a rare bleeding disorder that presents complex challenges in patient assessment and bleeding risk management. Despite generally causing mild to moderate bleeding symptoms, clinical manifestations can vary, and bleeding tendency does not always correlate with FXI plasma levels or genotype. Our manuscript delves into the age-related nuances of FXI deficiency across an individual's lifespan. We emphasize issues faced by specific groups, including neonates and females of reproductive age experiencing abnormal uterine bleeding and postpartum hemorrhage. Older patients present unique challenges and concerns related to the management of bleeding as well as thrombotic complications. The current assortment of diagnostic laboratory assays shows limited success in predicting bleeding risk in the perisurgical setting of patients with FXI deficiency. This review explores the intricate interplay between individual bleeding profiles, surgical sites, and FXI activity levels. We also evaluate the accuracy of existing laboratory assays in predicting bleeding and discuss the potential role of investigational global assays in perioperative assessment. Furthermore, we outline our suggested diagnostic approach to refine treatment strategies and decision making. Available treatment options are presented, including antifibrinolytics, replacement products, and recombinant activated FVII. Finally, we discuss promising nonreplacement therapies for the treatment of rare bleeding disorders that can potentially address the challenges faced when managing FXI deficiency-related bleeding complications.

Tissue factor pathway inhibitor is a potential modifier of bleeding risk in factor XI deficiency

BACKGROUND

Factor (F) XI deficiency is associated with increased bleeding risk in some individuals. Neither FXI levels nor clinical clotting assays predict the bleeding risk. Compared with controls, FXI-deficient bleeders have reduced clot formation, decreased fibrin network density, and increased susceptibility to fibrinolysis. Tissue factor pathway inhibitor (TFPI) was recently implicated as a modifying factor in individuals with bleeding of unknown cause.

OBJECTIVES

To determine the potential of TFPI in modifying the bleeding risk in FXI-deficient individuals.

METHODS

The effects of TFPI on thrombin generation and clot formation, structure, and fibrinolysis in FXI-deficient plasma were measured in vitro in the absence or presence of inhibitory anti-TFPI antibody or exogenous recombinant TFPIα. Total plasma TFPI concentration was measured in 2 independent cohorts of controls and FXI-deficient individuals classified as bleeders or nonbleeders (cohort 1: 10 controls and 16 FXI-deficient individuals; cohort 2: 48 controls and 57 FXI-deficient individuals) and correlated with ex vivo plasma clot formation and fibrinolysis parameters associated with bleeding risk.

RESULTS

In an in vitro FXI deficiency model, inhibition of TFPI enhanced thrombin generation and clot formation, increased the network density, and decreased fibrinolysis, whereas an increase in TFPI had the opposite effects. Compared with controls, plasma from FXI-deficient bleeders had higher TFPI concentration. Total plasma TFPI concentrations correlated with parameters from ex vivo clotting and fibrinolysis assays that differentiate FXI-deficient bleeders and nonbleeders.

CONCLUSION

Coagulation and fibrinolysis parameters that differentiate FXI-deficient nonbleeders and bleeders were altered by plasma TFPIα. Total plasma TFPI was increased in FXI-deficient bleeders. TFPI may modify the bleeding risk in FXI-deficient individuals.