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Background: Information on bleeding phenotype in nonsevere hemophilia may be used to determine target factor levels for prophylaxis or gene therapy in severe hemophilia., Objectives: To assess the association between endogenous factor level and bleeding phenotype in children with nonsevere (factor [F]VIII/FIX activity 1%-25%) hemophilia A (HA) and B without prophylaxis., Methods: Data on annualized bleeding rate (ABR), annualized joint bleeding rate (AJBR), and onset of bleeding were extracted from the international PedNet cohort including children born since 2000. Mean ABR and AJBR were modeled and compared according to FVIII/FIX endogenous activity (1%-2%, 3%-5%, 6%-10%, 11%-15%, 16%-20%, and 21%-25%) using negative binomial regression. Onset of bleeding was analyzed using Kaplan-Meier survival curves., Results: Eight hundred twenty-five children (40% with moderate hemophilia; 87% with HA) with median follow-up of 7.4 years/child were included. The median age at onset of bleeding and median bleeding rates changed with increasing endogenous activity. From endogenous FVIII 1% to 2% to 21% to 25%, the age at onset of bleeding changed from a median of 1.4 to 14.2 years, ABR from 1.6 to 0.1/y, and AJBR from 0.5 to 0.0/y. From endogenous FIX 1% to 2% to 16% to 25%, the onset of bleeding changed from a median of 1.7 to 6.1 years, ABR from 0.5 to 0.1/y, and AJBR from 0.1 to 0.0/y. The negative correlation between AJBR and factor level was most strongly pronounced up to a factor level of 6% in HA and hemophilia B., Conclusion: Endogenous factor activity of >5% was identified as a threshold to significantly lower joint bleeding rate, while FVIII levels >15% and FIX levels >10% were sufficient to achieve the goal of 0 bleeds in this pediatric cohort., Competing Interests: Declaration of competing interests This study is supported by the PedNet Haemophilia Research Foundation. Unrestricted sponsorship for the PedNet Haemophilia Research Foundation is currently received from Bayer AG, Takeda, Novo Nordisk, CSL Behring, Pfizer Inc, Swedish Orphan Biovitrum AB, Hoffmann-La Roche, and LFB Biotechnologies. M.S.d.K. has nothing to declare. C.E.-E. received grants, travel support, and/or honoraria from Bayer, BioMarin, Biotest, CSL Behring, Grifols, Kedrion, LFB, Octapharma, Novo Nordisk, Pfizer, Roche/Chugai, Sanofi, Sobi, and Takeda. C.K.’s institution has received grants for clinical trials and research from Bayer, Biotest, CSL Behring, Interseroh, Novo Nordisk, Pfizer, Roche/Chugai, Sobi/Sanofi, Takeda, the German Research Foundation (DFG), and the European Union. C.K. has received speaker’s fees and/or travel support from Bündnis zur Förderung der Sicherheit von Hämophilen (BFSH), Bayer, CSL Behring, MSD, Novo Nordisk, Roche/Chugai, Sobi/Sanofi, and Takeda. S.R.’s institution has received grants for research from the Childhood Cancer Foundation, PedNet, Stockholm County Council, and the Steering Committee of Roche. S.R. is investigator in clinical trials promoted by Novo Nordisk, Roche, and Sobi. K.F.’s institution has received speaker’s fees from CSL Behring, Novo Nordisk; consultancy fees from Biogen, CSL Behring, Freeline, Novo Nordisk, Roche, and Sobi; and research support from Bayer, Pfizer, and Novo Nordisk. K.F. is the epidemiologist for the European Haemophilia Safety Surveillance (EUHASS) and the PedNet Haemophilia Research Foundation., (Copyright © 2024 International Society on Thrombosis and Haemostasis. Published by Elsevier Inc. All rights reserved.)

For patients with hemophilia A and high-titer inhibitors treated with bypassing agents there are no reliable methods to assess treatment effect. We investigated the utility of global hemostatic methods in assessing treatment with bypassing agents (rFVIIa or activated prothrombin complex [aPCC]). All patients with hemophilia A and inhibitors followed at the Coagulation Unit or the Pediatric Coagulation Unit at Karolinska University Hospital aged 6 years and above were eligible for this noninterventional study. Baseline plasma samples were spiked with bypassing agents in increasing concentrations (aPCC 50 U/kg, 100 U/kg, 150 U/kg, and rFVIIa 90 μg/kg and 270 μg/kg) in vitro. For patients treated with factor concentrates or bypassing agents follow-up samples were collected (in vivo tests). The samples were analyzed using overall hemostatic potential (OHP), and calibrated automated thrombogram, Calibrated Automated Thrombogram (CAT). Nine patients with hemophilia A with inhibitors were included. Spiking with rFVIIa normalized the coagulation potential in 6/8 samples, in 3 only with high dose. Only one sample did not improve adequately after spiking with aPCC. The improvement in hemostasis was reliably shown by both CAT and OHP. The baseline potential was, however, more often measurable by OHP compared to CAT. Factor concentrate had been administered to 5 patients normalizing the hemostatic potential in vivo in 2 (without spiking). The hemostatic improvement induced by spiking with rFVIIa or aPCC is shown by OHP and CAT, but the results have to be evaluated in larger cohorts., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: Roza Chaireti has received an Investigator-Initiated Research grant (IIR-SWE-BXLT-001972/IISR-2017-104237) by Baxalta US Inc, now part of Takeda group of companies. Susanna Ranta is an investigator in clinical trials sponsored by Boehringer Ingelheim, Novo Nordisk, Roche and Sobi; member of a steering committee for Roche; and has received grants for research from the Childhood Cancer Foundation and Stockholm County Council. Pia Petrini has received speakers fee and consultant from Bayer, Novo Nordisk, Sobi, Taked/Shire and Roche. Maria Magnusson is an investigator in clinical trials sponsored by Sobi, Roche, Novo Nordisk, Octapharma. Honoraria as member of advisory board and/or speaker from Sobi, BioMarin, Pfizer, CSL-Behring, NovoNordisk (payment to institution, not to author). Grants for research from Stockholm County Council. Jovan P. Antovic has received research grants from Sobi, CSL Behring and Bayer, honoraria from Stago, Siemens, Sysmex, Roche, Baxter, Takeda and Sobi, and acted on advisory boards for NovoNordisk and Sobi. Nida Soutari, Margareta Holmström and Iva Pruner have no conflicts of interest to declare.

Background:  Discrepancy in factor IX activity (FIX:C) between one-stage assay (OSA) and chromogenic substrate assay (CSA) in patients with hemophilia B (PwHB) introduces challenges for clinical management., Aim:  To study the differences in FIX:C using OSA and CSA in moderate and mild hemophilia B (HB), their impact on classification of severity, and correlation with genotype., Methods:  Single-center study including 21 genotyped and clinically characterized PwHB. FIX:C by OSA was measured using ActinFSL (Siemens) and CSA by Biophen (Hyphen). In addition, in vitro experiments with wild-type FIX were performed. Reproducibility of CSA was assessed between three European coagulation laboratories., Results:  FIX:C by CSA was consistently lower than by OSA, with 10/17 PwHB having a more severe hemophilia type by CSA. OSA displayed a more accurate description of the clinical bleeding severity, compared with CSA. A twofold difference between OSA:CSA FIX:C was present in 12/17 PwHB; all patients had genetic missense variants in the FIX serine protease domain. Discrepancy was also observed with diluted normal plasma, most significant for values below 0.10 IU/mL. Assessment of samples with low FIX:C showed excellent reproducibility of the CSA results between the laboratories., Conclusion:  FIX:C was consistently higher by OSA compared with the CSA. Assessing FIX:C by CSA alone would have led to diagnosis of a more severe hemophilia type in a significant proportion of patients. Our study suggests using both OSA and CSA FIX:C together with genotyping to classify HB severity and provide essential information for clinical management., Competing Interests: R.L. has during the past 3 years received consultancy or speaker's fee from Idogen AB, Sobi, Novo Nordisk, Takeda, Sanofi, and Bayer; none of these are related to the present work. M.B. has been a member on advisory boards for CSL Behringer, Idogen, Novo Nordisk, and Sobi, had consultant assignments for Novo Nordisk, and received lecturer honoraria from Pfizer and Sobi. S.R. was investigator in clinical trials sponsored by Sobi, Roche, Novo Nordisk; holds grants for research from the Childhood Cancer Foundation and Stockholm County Council; and has been on Steering Committee for Roche. The other authors stated that they had no interests which might be perceived as posing a conflict or bias., (Thieme. All rights reserved.)

Introduction: Haemophilia A care has changed with the introduction of emicizumab. Experience on the youngest children is still scarce and clinical practice varies between haemophilia treatment centres., Aim: We aimed to assess the current clinical practice on emicizumab prophylaxis within PedNet, a collaborative research platform for paediatricians treating children with haemophilia., Methods: An electronic survey was sent to all PedNet members (n = 32) between October 2022 and February 2023. The survey included questions on the availability of emicizumab, on the practice of initiating prophylaxis in previously untreated or minimally treated patients (PUPs or MTPs) and emicizumab use in patients with or without inhibitors., Results: All but four centres (28/32; 88%) responded. Emicizumab was available in clinical practice in 25/28 centres (89%), and in 3/28 for selected patients only (e.g. with inhibitors). Emicizumab was the preferred choice for prophylaxis in PUPs or MTPs in 20/25 centres; most (85%) started emicizumab prophylaxis before 1 year of age (30% before 6 months of age) and without concomitant FVIII (16/20; 80%). After the loading dose, 13/28 centres administered the recommended dosing, while the others adjusted the interval of injections to give whole vials. In inhibitor patients, the use of emicizumab during ITI was common, with low-dose ITI being the preferred protocol., Conclusion: Most centres choose to initiate prophylaxis with emicizumab before 12 months of age and without concomitant FVIII. In inhibitor patients, ITI is mostly given in addition to emicizumab, but there was no common practice on how to proceed after successful ITI., (© 2023 The Authors. Haemophilia published by John Wiley & Sons Ltd.)

Introduction: Good health-related quality of life (HRQoL) is an important goal in the treatment of persons with haemophilia B (PwHB). Studies focusing on this population are limited, however, and data are insufficient., Aim: To assess the HRQoL in PwHB and to compare this to data on persons with haemophilia A (PwHA), as well as to evaluate the impact of joint health on HRQoL and to identify areas of insufficient care., Methods: The B-NORD study enrolled persons with severe haemophilia B and matched controls with haemophilia A. HRQoL was assessed using the EQ-5D-3L questionnaire and joint health using Haemophilia Joint Health Score 2.1 (HJHS)., Results: The EQ-5D-3L was completed by 63 PwHB and 63 PwHA. Mobility problems were reported by 46% of PwHB and 44% of PwHA, pain/discomfort by 62% and 56%, and anxiety/depression by 33% and 17%, respectively. No significant difference was observed between PwHA and PwHB in EQ-5D profiles, level sum score, EQ-5D index (PwHB mean .80, PwHA mean .83, p = .24), or EQ VAS score (PwHB: mean 70, PwHA: mean 77, p = .061). Linear regression adjusted for age demonstrated that an increase in HJHS score was associated with a significant decrease in both EQ-5D index (B -.003, R 2 .22) and EQ VAS score (B -.37, R 2 .17)., Conclusion: Despite the majority of patients being treated with prophylaxis, impaired HRQoL was reported in both PwHB and PwHA. No differences in HRQoL were found between the two groups. Impaired joint health had a significant negative impact on HRQoL., (© 2023 The Authors. Haemophilia published by John Wiley & Sons Ltd.)

Introduction: Favourable joint outcomes are expected with modern haemophilia A (HA) management. Evaluation of long-term treatment outcomes is hampered by the delay between bleeding episodes during childhood and resulting joint outcomes in adulthood., Aim: To measure the long-term joint health of adolescents with moderate and severe HA, according to severity and inhibitor status., Methods: Pilot cross-sectional study of five European PedNet centres in moderate and severe HA patients aged 10-19 years. Structured assessment of joint status by physical examination (HJHS) and ultrasound (HEAD-US)., Results: In total, 141 HA patients were evaluable, 100 without inhibitors (81 severe, 19 moderate HA), and 41 severe HA with current/past inhibitors. On physical examination, 12/81 (15%) of severe HA without inhibitors, 3/19 (16%) of moderate HA, and 13/41 (32%) of severe HA patients with inhibitors exhibited joint abnormalities. Inhibitor persistence, longer inhibitor duration, and a high peak inhibitor level were associated with impaired joint health. Ultrasound showed joint damage (bone or cartilage) in 13/49 (27%) of severe HA without inhibitors, 1/12 (8%) of moderate HA, and 10/28 (36%) of severe HA patients with inhibitors. A discordant ankle evaluation by ultrasound versus physical examination was present in 53/169 joints (31%)., Conclusions: Most adolescents with severe or moderate HA show favourable joint health. Future research with combined ultrasound and/or MRI is needed to better understand joint outcomes in the remaining patients. Patents with inhibitors showed a two-fold increased proportion with joint deterioration. Ultrasound paired with physical examination increases sensitivity for detection of joint damage., (© 2022 The Authors. Haemophilia published by John Wiley & Sons Ltd.)

Introduction: The development of inhibitory antibodies (inhibitors) in persons with hemophilia B (PwHB) causes significant morbidity. Data on the impact of the F9 variant and immune tolerance induction (ITI) outcome are limited. The aim of this study was to investigate the presence of neutralizing and non-neutralizing antibodies (NNA) in severe hemophilia B (HB) and to evaluate ITI outcome and complications in relation to the pathogenic F9 variant., Materials and Methods: Persons with severe HB in the Nordic countries were enrolled and information on F9 variants, inhibitors, ITI and complications were collected. Analyses of anti-FIX antibodies with a fluorescence-immunoassay (xFLI) and an ELISA method were conducted., Results: Seventy-nine PwHB were enrolled. Null variants were seen in 33 (42 %) PwHB and 12 (15 %) had a current or former inhibitor. Eleven (92 %) of the inhibitor patients had experienced allergic manifestations and three (25 %) nephrotic syndrome. Of 10 PwHB with at least one ITI attempt, eight (80 %) were considered tolerant at enrolment. Immunosuppression was included in seven of eight successful or partially successful attempts. Five PwHB had at least one ITI failure before a successful or partially successful ITI. No NNA could be identified., Conclusion: A high proportion of severe F9 gene defects among persons with severe HB in the Nordic countries may explain the observed relatively high prevalence of inhibitors. ITI success was independent of the F9 variant and attained despite allergic manifestations and previous ITI failures. Inclusion of immunosuppression tentatively enhances the chances of ITI success. No NNA were observed., (Copyright © 2022. Published by Elsevier Ltd.)

Introduction: Data on outcome in persons with haemophilia B (PwHB) are limited and mainly extrapolated from studies of haemophilia A (HA)., Aim: To characterize treatment outcomes in persons with severe HB in the Nordic region, with a focus on joint health, compared with matched controls with HA., Methods: PwHB attending haemophilia centres in Denmark, Finland, Norway and Sweden were enrolled and matched with controls with HA. Joint assessment using Haemophilia Joint Health Score (HJHS) and ultrasound according to Haemophilia Early Arthropathy Detection protocol (HEAD-US) was conducted. Adherence was evaluated using the Validated Haemophilia Regimen Treatment Adherence Scale (VERITAS)., Results: Seventy-nine males with HB, with median age of 30 years (range 1-75), were enrolled. Eleven patients (14%) had a history of or current inhibitor. Twenty-nine PwHB (37%) reported joint bleeds during the prior year, and 35% had previously undergone joint surgery. Ninety-five per cent were on prophylaxis, and 70% used recombinant concentrates, with a median factor consumption of 3,900 IU/kg/year for standard half-life products. Only two patients had a VERITAS score corresponding to 'non-adherence'. Joint health, assessed with HJHS, showed a significant lower score among PwHB compared with HA controls, explained by a difference in the 18-49 age group, without observed differences in older or younger subgroups. The HEAD-US scores were overall low., Conclusion: The Nordic cohort of PwHB is well treated by prophylaxis, but the goal of zero bleeds for all is not reached. Our findings suggest that patients with severe HB suffer from a milder arthropathy than patients with severe HA., (© 2021 The Authors. Haemophilia published by John Wiley & Sons Ltd.)

Introduction: Central venous access devices facilitate home treatment in boys with haemophilia. These are usually fully implanted lines, referred to as ports. Caregivers are taught to manage the port using sterile techniques and maintaining patency by flushing with saline or heparin solution. National and international guidelines for the home care of ports are lacking., Aim: To evaluate if infection or occlusion rates differ between home care regimens used for ports in children with haemophilia., Methods: Children with ports were identified from the PedNet registry. Data on the homecare policy were acquired from each centre. To ensure a complete data set for each port, only ports that had been removed were included in the study. Three care groups were defined: 'aseptic non touch technique', 'sterile technique' and 'fully sterile technique'. Outcomes within and between the groups were analysed., Results: A total of 240 children with 352 ports were studied. Insertion occurred at a median age of 1.32 years. The median port duration was 2.94 years with a total of 215 688 port days in children without and 183 852 in children with inhibitors. Infection was the most common cause of port removal (34%); there was no significant difference with infection as reason for removal between the different care groups. Occlusion was not more frequent in centres that did not use heparin., Conclusion: Use of sterile gloves and gowns did not reduce the risk of port infection. Using less stringent sterile techniques for accessing ports is easier for caregivers and in addition may have health economic benefits., (© 2017 Crown copyright. Haemophilia © 2017 John Wiley & Sons Ltd.)

Adults with haemophilia have a higher incidence of chronic kidney disease than general male population. We recently showed that children with haemophilia have higher urinary calcium excretion and lower whole body bone mineral density than controls in spite of prophylaxis with the deficient coagulation factor concentrate, serum vitamin D concentrations comparable to those of healthy children and physically active lifestyle. Persistent hypercalciuria may result in nephrocalcinosis and impact renal function. This study sought to assess persistence of urinary calcium excretion and kidney function in children with haemophilia. We investigated retrospectively urinary calcium excretion in 30 children with haemophilia (mean age 12.5 years) from consecutive urine samples over a 2-year period. Renal evaluation included blood and urine specimen, blood pressure, and renal ultrasound. High number of children with haemophilia had intermittent hypercalciuria. Hypercalciuria was not associated with age, severity of haemophilia or previous hypercalciuria. Kidney function and renal ultrasound were normal with the exception of suspected kidney stone in one patient with haemophilia and transient hypercalciuria. Vitamin D concentrations improved after the families had received information and recommendations concerning vitamin D substitution. Our findings indicate that haemophilia per se predisposes to hypercalciuria which may in turn affect bone mineral content and kidney function. Whether childhood-onset intermittent hypercalciuria contributes to hypertension and renal complications in adulthood remains to be elucidated in future studies., (© 2012 Blackwell Publishing Ltd.)

Children with haemophilia are at risk of suboptimal bone mass accrual and low bone mineral density (BMD). We recently demonstrated that although BMD in Finnish children with haemophilia was within the normal range, their whole body BMD was significantly lower and hypercalciuria more prevalent than in controls. This study sought to determine the bone structure and strength in physically active children with haemophilia. To investigate the underlying mechanisms in this group, we conducted a case-control study to assess bone structure and strength by peripheral quantitative computed tomography (pQCT) at the radius. The study group comprised 29 patients (mean age 12.2 years) and 46 age-matched controls. Children with haemophilia had decreased total BMD Z-score at the distal radius (P ≤ 0.001), but increased cortical bone density at the proximal radius (P ≤ 0.001). Total bone area at the proximal radius was significantly lower in children with haemophilia (P = 0.002), whereas there were no differences in cortical bone area or in polar Strength-Strain Index, a parameter of bone strength, between the patients and controls. Patients with mild to moderate haemophilia and on-demand treatment had inferior bone strength compared to those with moderate to severe haemophilia and prophylaxis. Our findings suggest altered skeletal development in patients with haemophilia in the radius, resulting in smaller bone size and higher cortical bone density. Importantly, bone strength at the radius appears equal to healthy children. Prophylactic treatment seems to have a beneficial effect on bone health., (© 2012 Blackwell Publishing Ltd.)

Central venous access devices (CVADs) are often required in children with haemophilia to secure venous access for prophylactic treatment or immune tolerance therapy. Complications of CVADs include infections, thrombosis and mechanical problems. This study sought to determine the outcome of the vessels by magnetic resonance imaging (MRI) in children with haemophilia and to assess risk factors for development of catheter-related deep venous thrombosis (DVT). After the removal of CVAD an MRI of the chest and neck was performed to 20 boys with haemophilia who each had 1-3 (total number 27) CVADs placed. MRI revealed DVT in five children (25%). As their CVADs were functional at the time of the removal, the DVTs were clinically silent. However, there had been suspicion of DVT leading to replacement of the CVAD in one case. All the children with DVT had their CVADs inserted initially below the age of 1 year. The clinical signs of mild post-thrombotic syndrome (PTS) were common: dilated chest wall veins were observed in 11 (55%) children and were associated with DVT in three cases. Arm circumference discrepancy was observed in one child with DVT. No correlation between the duration or number of CVADs and DVT was detected. None of the patients had subjective symptoms of PTS. Silent DVT is a common complication of CVAD. Catheter insertion at a young age seems to predispose to thrombosis. The long-term consequences of the DVTs remain unknown., (© 2011 Blackwell Publishing Ltd.)

Several factors can compromise optimal bone mass accrual during childhood and predispose to osteoporosis later in life. Patients with haemophilia are already at risk of low bone mass during childhood, partly due to reduced physical activity related to joint bleeds and haemarthrosis. The introduction of primary prophylaxis with regular infusions of the deficient coagulation factor has enabled reduction or prevention of haemophilic arthropathy. Finnish children with severe haemophilia start prophylaxis early and are encouraged to participate in physical activities. We hypothesized that prophylactic therapy would ensure normal childhood bone mass development and carried out a case-control study in 29 children with haemophilia (2 mild, 6 moderate, 21 severe) and 58 age-matched controls. Their bone health was determined by fracture history, blood and urine biochemistry, bone densitometry and spinal imaging. Bone mineral density was lower in children with haemophilia but there was no evidence for significantly increased fracture rate. The patients had significantly higher urinary calcium excretion and higher serum calcium concentration, and reduced bone resorption as compared with the controls. Our findings suggest primary skeletal pathology, resulting in increased urinary calcium loss and altered bone metabolism, which may over time contribute to the development of osteoporosis in patients with haemophilia., (© 2011 Blackwell Publishing Ltd.)

The aim of the investigation described was to study experiences and views about hemophilia, genetic counseling, carrier testing, and termination of pregnancy among first-degree female relatives of Finnish hemophilia A patients. Altogether, 167 women participated in the study, which was carried out by a mailed multiple-choice questionnaire. For comparison, a copy of the questionnaire was asked to be given to the spouse. Hemophilia was considered a serious disease. Most women knew well their risk of carriership and of having an affected son. Hemophilia was considered a slightly more acceptable reason for abortion than poor social circumstances. In case of an affected male fetus, 16% of the women would definitely terminate the pregnancy. The majority of participants wished to hear the genetic counselor's view on family planning and termination of pregnancy. The opinions of the spouses were concordant with those of the women.