Patients with moderate hemophilia A and B with a severe bleeding phenotype have an increased burden of disease.

BACKGROUND: Patients with moderate hemophilia express varying bleeding phenotypes. OBJECTIVES: To assess the burden of disease in patients with moderate hemophilia and a mild or severe phenotype incorporating the thrombin generation profile. METHODS: This sub-study of the 6th Hemophilia in the Netherlands study, analyzed data of adults with moderate hemophilia A or B. Patient characteristics and information on bleeding tendency, joint status, and quality of life were obtained from electronic patient files and self-reported questionnaires. A severe bleeding phenotype was defined as an annual bleeding rate ≥5, an annual joint bleeding rate ≥3, and/or the use of secondary/tertiary prophylaxis, and a mild phenotype vice versa. TG was measured with the Nijmegen Hemostasis Assay. RESULTS: This study included 116 patients: 21% had a severe phenotype of whom 46% used prophylaxis. Patients with a severe phenotype treated on demand reported a higher median annual bleeding rate (7), annual joint bleeding rate (3), and more frequently an impaired joint (77%) than patients with a severe phenotype on prophylaxis (2; 0; 70%) or patients with a mild phenotype (0; 0; 47%). Furthermore, patients with a severe phenotype treated on demand experienced a more decreased quality of life. Despite similar factor activity levels, patients with a severe phenotype had a lower thrombin peak height and thrombin potential (0.7%; 0.06%) than patients with a mild phenotype (21.3%; 46.8%). CONCLUSION: Patients with moderate hemophilia and a severe phenotype treated on demand displayed a high burden of disease as well as a low thrombin generation profile advocating them toward more intensive prophylactic treatment.

The Nijmegen ultra-sensitive Bethesda Assay detects very low-titer factor VIII inhibitors in patients with congenital and acquired hemophilia A.

BACKGROUND: An inhibitor can develop in congenital hemophilia A (HA) patients against exogenous infused factor (F)VIII, whereas in acquired HA (AHA) inhibitors initially develop against endogenous FVIII. Inhibitors can be detected with the Nijmegen Bethesda Assay (NBA), which has an international cut-off level of 0.60 Nijmegen Bethesda Units/mL (NBU/mL). Thereby, very low-titer inhibitors may remain undetected. AIM: To describe the design and validation of the Nijmegen ultra-sensitive Bethesda Assay (NusBA) for the detection of very low-titer inhibitors. METHODS: The NusBA is a modification of the NBA in which the ratio of patient plasma to normal pooled plasma is changed from 1:1 to 9:1. Analytical validation was performed according to the CLSI EP10 guideline in order to determine trueness and reproducibility. Clinical validation was performed in two cohorts of congenital HA patients (82 adults) with pharmacokinetic data and four AHA patients. The limit of quantitation (LOQ) was determined by measuring plasma samples spiked with inhibitor levels in the low range (0.05-0.80 NBU/mL). RESULTS: The LOQ for the NusBA was 0.10 NusBU/mL, with a coefficient of variation of 24.2 %. Seven (8.5 %) congenital HA patients had a positive NusBA result, of which only one was detected with the NBA. There was no correlation between NusBA and FVIII half-life. In three of the AHA patients the NusBA remained positive, when the NBA became negative. DISCUSSION: The NusBA is able to detect very low-titer FVIII inhibitors of ≥0.10 NBU/mL. Thereby, it may have added value in early inhibitor detection and therapy adjustments in patients with congenital HA and AHA.

In patients with hemophilia, a decreased thrombin generation profile is associated with a severe bleeding phenotype.

Background: Heterogeneity in clinical bleeding phenotype has been observed in hemophilia patients with similar FVIII or FIX activity levels. Thrombin generation and plasmin generation, as a global hemostasis assay, may contribute to a better prediction of which patients are at an increased risk of bleeding. Objectives: The objective of this study was to describe the association between clinical bleeding phenotype and thrombin generation and plasmin generation profiles in patients with hemophilia. Methods: The Nijmegen Hemostasis Assay, which simultaneously measures thrombin and plasmin generation, was performed in plasma samples of patients with hemophilia participating in the sixth Hemophilia in the Netherlands study (HiN6). Patients receiving prophylaxis underwent a washout period. A severe clinical bleeding phenotype was defined as a self-reported annual bleeding rate of ≥5, a self-reported annual joint bleeding rate of ≥3, or the use of secondary/tertiary prophylaxis. Results: In total, 446 patients, with a median age of 44 years, were included in this substudy. Thrombin generation and plasmin generation parameters differed between patients with hemophilia and healthy individuals. The median thrombin peak height was 1.0 nM, 25.9 nM, 47.1 nM, and 143.9 nM in patients with severe, moderate, and mild hemophilia and healthy individuals, respectively. A severe bleeding phenotype was observed in patients with a thrombin peak height of <49% and a thrombin potential of <72% compared to healthy individuals, and was independent of the hemophilia severity. The median thrombin peak height was 0.70% in patients with a severe clinical bleeding phenotype and 30.3% in patients with a mild clinical bleeding phenotype. The median thrombin potentials for these patients were 0.06% and 59.3%, respectively. Conclusion: A decreased thrombin generation profile is associated with a severe clinical bleeding phenotype in patients with hemophilia. Thrombin generation in combination with bleeding severity may be a better tool to personalize prophylactic replacement therapy irrespective of hemophilia severity.

Thrombin generation for monitoring hemostatic therapy in hemophilia A: A narrative review.

Patients with severe hemophilia A (HA) have an increased risk of spontaneous and trauma-related bleeding because of a congenital absence of factor VIII (FVIII). Most severe HA patients use prophylactic FVIII concentrate, the effect of which can be monitored with FVIII activity level measurement. However, FVIII activity level is less valuable in predicting the potential clinical bleeding risk. Some patients still experience breakthrough bleeds despite adequate FVIII trough levels, whereas others do not bleed with trough levels below threshold. This difference may be caused by inter-individual differences in pro- and anticoagulant factors, the so-called hemostatic balance. Thrombin generation assays (TGAs) measure the hemostatic balance as a whole. Thereby, the TGAs may be a better tool in the guidance and monitoring of treatment in HA patients. In addition, TGAs offer the opportunity to determine the response to bypassing agents and treatment with non-factor replacement therapy, in which FVIII activity assays are not suitable for monitoring. This review summarizes the current knowledge about monitoring different HA treatment modalities by TGA, as a single treatment option and when used in a concomitant fashion.

Bleeding severity in patients with rare bleeding disorders: real-life data from the RBiN study.

Patients with hereditary rare bleeding disorders (RBDs) present with diverse hemorrhagic symptoms. Correlation between factor activity levels and clinical bleeding severity is poor for most RBDs. Threshold factor activity levels have been previously described in relation to bleeding severity but have not yet been validated. The Rare Bleeding Disorders in the Netherlands (RBiN) study is a nationwide cross-sectional study of patients registered in all 6 Dutch Haemophilia Treatment Centers with a known RBD and who are age 1 to 99 years. Bleeding scores were determined, and laboratory and clinical data were extracted from patient files. In all, 263 patients were included, of whom 202 (77%) attended the scheduled study visit. The median International Society of Thrombosis and Haemostasis (ISTH) bleeding assessment tool (BAT) score was 9. Correlations between baseline factor activity levels and ISTH BAT scores were strong for deficiencies in factor II (FII) (r = -0.792) and FX (r = -0.838) and were moderate for deficiencies of fibrinogen (r = -0.683), FV (r = -0.623), FVII (r = -0.516), FXIII (r = -0.516), and α2-antiplasmin (r = -0.594). There was no correlation for FXI deficiency (r = -0.218). The RBD BAT identified more women (94% vs 83%) and children (100% vs 71%) with an RBD than the ISTH BAT did. Importantly, 48% of patients had more severe bleeding than predicted for their baseline factor activity level. In addition, 34% of patients were predicted to be asymptomatic, but they actually had grade 2 (31%) or 3 (3%) bleeding. Bleeding severity in patients with RBDs is more pronounced than previously anticipated. The previously determined threshold factor activity levels to ensure no (spontaneous) bleeding in patients with an RBD are inaccurate. This trial was registered at www.clinicaltrials.gov as #NCT03347591.