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

Platelet function analyzer (PFA-100) in patients with mild-to-moderate bleeding disorders and bleeding disorder of unknown cause

BACKGROUND

The sensitivity of the platelet function analyzer (PFA-100, Dade Behring Inc) was shown to be high for the detection of von Willebrand disease (VWD), but limited for platelet function defects.

OBJECTIVES

To study the diagnostic utility of PFA-100 in mild-to-moderate bleeding disorders and bleeding disorder of unknown cause (BDUC).

METHODS

PFA-100 closure times (CTs) were measured with collagen-epinephrine (EPI) and collagen-adenosine diphosphate (ADP) cartridges in 818 patients with mild bleeding disorders from the Vienna Bleeding Biobank. Patients on anticoagulation or antiplatelet therapy or thrombocytopenic patients were not included.

RESULTS

Only 2% of the 532 BDUC patients had prolonged CTs in PFA (EPI) and PFA (ADP), and 64% in either PFA (EPI) or PFA (ADP). In total, 34% of BDUC patients did not have prolonged CTs in PFA (EPI) or PFA (ADP). These rates were similar to patients with coagulation factor deficiencies (n = 27). The rate of pathologic CTs was significantly higher in patients with VWD (n = 79) and, although less pronounced, in platelet function defect (n = 180). In 15 of 18 (83%) VWD patients with von Willebrand factor (VWF) antigen and/or VWF ristocetin cofactor activity levels <30 IU/dL, the PFA-100 was prolonged in both cartridges. No association of the PFA-100 with the bleeding severity was observed in BDUC patients. However, prolonged CTs were associated with higher age, lower hematocrit, lower VWF antigen or VWF ristocetin cofactor activity levels, lower platelet counts, and higher fibrinogen levels in BDUC patients.

CONCLUSION

We could not confirm a diagnostic utility for the PFA-100 in mild-to-moderate bleeding disorder patients, and specifically BDUC. No association between PFA-100 results and bleeding severity was observed in BDUC patients.

The Mechanisms of Sepsis Induced Coagulation Dysfunction and Its Treatment

Sepsis is a critical condition characterized by organ dysfunction due to a dysregulated response to infection that poses significant global health challenges. Coagulation dysfunction is nearly ubiquitous among sepsis patients. Its mechanisms involve platelet activation, coagulation cascade activation, inflammatory reaction imbalances, immune dysregulation, mitochondrial damage, neuroendocrine network disruptions, and endoplasmic reticulum (ER) stress. These factors not only interact but also exacerbate one another, leading to severe organ dysfunction. This review illustrates the mechanisms of sepsis-induced coagulopathy, with a focus on tissue factor activation, endothelial glycocalyx damage, and the release of neutrophil extracellular traps (NETs), all of which are potential targets for therapeutic interventions.

The foundation for investigating factor XI as a target for inhibition in human cardiovascular disease

Anticoagulant therapy is a mainstay in the management of patients with cardiovascular disease and related conditions characterized by a heightened risk for thrombosis. Acute coronary syndrome, chronic coronary syndrome, ischemic stroke, and atrial fibrillation are the most common. In addition to their proclivity for thrombosis, each of these four conditions is also characterized by local and systemic inflammation, endothelial/endocardial injury and dysfunction, oxidative stress, impaired tissue-level reparative capabilities, and immune dysregulation that plays a critical role in linking molecular events, environmental triggers, and phenotypic expressions. Knowing that cardiovascular disease and thrombosis are complex and dynamic, can the scientific community identify a common pathway or specific point of interface susceptible to pharmacological inhibition or alteration that is likely to be safe and effective? The contact factors of coagulation may represent the proverbial "sweet spot" and are worthy of investigation. The following review provides a summary of the fundamental biochemistry of factor XI, its biological activity in thrombosis, inflammation, and angiogenesis, new targeting drugs, and a pragmatic approach to managing hemostatic requirements in clinical trials and possibly day-to-day patient care in the future.

Targeting tissue factor pathway inhibitor with concizumab to improve hemostasis in patients with Glanzmann thrombasthenia: an in vitro study

BACKGROUND

Glanzmann thrombasthenia (GT) is caused by an inherited defect of platelet αIIbβ3 integrin. Concizumab, a monoclonal antibody specific for tissue factor pathway inhibitor, abolishes its anticoagulant effect.

OBJECTIVES

To evaluate the in vitro ability of concizumab to improve hemostasis in GT.

METHODS

The effects of concizumab were evaluated in whole blood or platelet-rich plasma from GT patients (n = 5-9) using a thrombin generation assay, rotational thromboelastometry (ROTEM), a global fibrinolytic capacity assay, and a flow chamber assay (Total Thrombus formation Analysis System). Washed platelets (WPs) and 20 nM recombinant activated factor VII (rFVIIa) were included for comparison.

RESULTS

The lag time in the thrombin generation assay was significantly longer (+85%; P < .0001) in GT patients than in controls. WPs, rFVIIa, and concizumab each significantly improved thrombin generation profiles. The ROTEM clotting time (CT) was significantly longer in GT patients than in controls (677 seconds vs 523 seconds; P = .03). However, CT improved after adding WPs, rFVIIa, or concizumab. Under flow, occlusive thrombi were present in all healthy controls after 10 minutes, whereas platelet-fibrin depositions were not seen in GT patients. Subocclusive or occlusive thrombi formed when GT blood was mixed with WPs, rFVIIa, or concizumab. Clots in GT platelet-rich plasma were more susceptible to fibrinolysis and were improved by WPs, rFVIIa, or concizumab.

CONCLUSION

Concizumab enhanced thrombin generation, decreased the ROTEM CT, improved thrombus formation under flow, and reduced clot lysis. Our results demonstrate the potential of concizumab for subcutaneous prophylaxis in GT patients.

Bleeding Disorder of Unknown Cause: A Diagnosis of Exclusion

Patients with an unexplained mild to moderate bleeding tendency are diagnosed with bleeding disorder of unknown cause (BDUC), a classification reached after ruling out other mild to moderate bleeding disorders (MBD) including von Willebrand disease (VWD), platelet function defects (PFDs), coagulation factor deficiencies (CFDs), and non-hemostatic causes for bleeding. This review outlines our diagnostic approach to BDUC, a diagnosis of exclusion, drawing on current guidelines and insights from the Vienna Bleeding Biobank (VIBB). According to guidelines, we diagnose VWD based on VWF antigen and/or activity levels ≤50 IU/dL, with repeated VWF testing if VWF levels are <80 IU/dL. This has been introduced in our clinical routine after our findings of diagnostically relevant fluctuations of VWF levels in a high proportion of MBD patients. PFDs are identified through repeated abnormalities in light transmission aggregometry (LTA), flow cytometric mepacrine fluorescence, and glycoprotein expression analysis. Nevertheless, we experience diagnostic challenges with regard to reproducibility and unspecific alterations of LTA. For factor (F) VIII and FIX deficiency, a cutoff of 50% is utilized to ensure detection of mild hemophilia A or B. We apply established cutoffs for other rare CFD being aware that these do not clearly reflect the causal role of the bleeding tendency. Investigations into very rare bleeding disorders due to hyperfibrinolysis or increase in natural anticoagulants are limited to cases with a notable family history or distinct bleeding phenotypes considering cost-effectiveness. While the pathogenesis of BDUC remains unknown, further explorations of this intriguing area may reveal new mechanisms and therapeutic targets.

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.

Risk factors for future bleeding in patients with mild bleeding disorders: longitudinal data from the Vienna Bleeding Biobank

BACKGROUND

The future bleeding risk, especially after hemostatic challenges, and thus the requirement for hemostatic treatment in patients with mild-to-moderate bleeding disorders (MBDs) is largely unknown.

OBJECTIVES

This study aimed to prospectively examine the recurrence of bleeding symptoms and clinical risk factors for future bleeding in patients with MBD, including patients with bleeding disorder of unknown cause (BDUC).

METHODS

Bleeding symptoms of patients with MBD included in the Vienna Bleeding Biobank were re-evaluated at in-person follow-up visits or by mail.

RESULTS

In total, 392 patients, including 62.8% with BDUC, were investigated for the recurrence of bleeding events. During the follow-up time of median (IQR) 4.3 years (2.6-6.7), 72% of patients had at least 1 bleeding event. Most persistent bleeding manifestations were hematomas (n = 146/245, 59.6%) and bleeding from small wounds (n = 69/141, 48.9%), followed by epistaxis (n = 42/132, 31.8%), oral mucosal bleeding (n = 26/87, 29.9%), and joint bleeding (n = 7/14, 50.0%). Patients with previous postinterventional bleeding had a significantly increased risk for bleeding events after surgery (n = 33/114, 29.0 %) or tooth extraction (n = 16/39, 41.0%). A high bleeding score (OR [95% CI], 1.14 [1.05 to 2.94], per 1 unit) and follow-up time (OR [95% CI], 1.23 [1.12 to 1.36], per 1 year) were independently associated with any bleeding event. For bleeding after hemostatic challenges, blood group O (OR, 3.17 [1.57 to 6.40]), previous postsurgical bleeding (OR, 2.40 [1.06 to 5.46]), and an established diagnosis (OR, 2.07 [1.04 to 4.10]) were independent risk factors.

CONCLUSION

Patients with MBD have a high risk for recurrent bleeding. This encourages prophylactic hemostatic treatment in patients with MBD, particularly when they face hemostatic challenges.