Key Points• The inhibitor incidence in nonsevere hemophilia A patients with certain F8 mutations approaches the inhibitor incidence in severe patients.• These findings are highly relevant for clinical practice, as they facilitate identification of high-risk patients based on F8 genotype.Neutralizing antibodies (inhibitors) toward factor VIII form a severe complication in nonsevere hemophilia A, profoundly aggravating the bleeding pattern. Identification of high-risk patients is hampered by lack of data that take exposure days to therapeutic factor VIII concentrates into account. In the INSIGHT study, we analyzed the association between F8 mutation and inhibitor development in patients with nonsevere hemophilia A (factor VIII 2-40 IU/dL). This analysis included 1112 nonsevere hemophilia A patients from 14 centers in Europe and Australia that had genotyped at least 70% of their patients. Inhibitor risk was calculated as KaplanMeier incidence with cumulative number of exposure days as the time variable. During 44 800 exposure days (median, 24 exposure days per patient; interquartile range [IQR], 7-90), 59 of the 1112 patients developed an inhibitor; cumulative incidence of 5.3% (95% confidence interval [CI], 4.0-6.6) after a median of 28 exposure days (IQR,. The inhibitor risk at 50 exposure days was 6.7% (95% CI, 4.5-8.9) and at 100 exposure days the risk further increased to 13.3% (95% CI, 9.6-17.0). Among a total of 214 different F8 missense mutations 19 were associated with inhibitor development. These results emphasize the importance of F8 genotyping in nonsevere hemophilia A. (Blood. 2013; 122(11):1954-1962 IntroductionPatients with hemophilia A who are treated with factor VIII concentrates are at risk of developing factor VIII neutralizing alloantibodies (inhibitors).1,2 Inhibitor development is one of the most challenging complications in the treatment of hemophilia A, as it increases the bleeding tendency while it renders treatment with therapeutic factor VIII concentrates ineffective. Although inhibitor development is less frequently observed in patients with nonsevere hemophilia A (baseline factor VIII activity of 2-40 IU/dL), the clinical impact can be profound. In these patients, inhibitors may also interact with their endogenous factor VIII, resulting in a decrease of the factor VIII plasma level below 1 IU/dL 1 and major bleeding complications. 4 Identification of patients at risk of developing inhibitors may help to prevent this serious complication. However, currently there are no tools available to predict individual inhibitor risk in nonsevere hemophilia patients.The type of mutation in the factor VIII gene (F8) is an important risk factor for inhibitor development. [5][6][7] Nonsevere hemophilia A is generally caused by F8 missense mutations.8 Despite information on large numbers of F8 mutations associated with nonsevere hemophilia A that is collected in international databases, 9,10 it is not possible to calculate the inhibitor risk for specific F8 mutations, as data on exposure days to thera...

To cite this article: Eckhardt CL, Menke LA, van Ommen CH, van der Lee JH, Geskus RB, Kamphuisen PW, Peters M, Fijnvandraat K. Intensive peri-operative use of factor VIII and the Arg593 fi Cys mutation are risk factors for inhibitor development in mild/moderate hemophilia A. See also Aledort LM. Mild and moderate factor VIII deficiency: inhibitor risks. This issue, pp 928-9.

Summary. Background: The life expectancy of non-severe hemophilia A (HA) patients equals the life expectancy of the non-hemophilic population. However, data on the effect of inhibitor development on mortality and on hemophilia-related causes of death are scarce. The development of neutralizing factor VIII antibodies in non-severe HA patients may dramatically change their clinical outcome due to severe bleeding complications. Objectives: We assessed the association between the occurrence of inhibitors and mortality in patients with non-severe HA. Methods: In this retrospective cohort study, clinical data and vital status were collected for 2709 non-severe HA patients (107 with inhibitors) who were treated between 1980 and 2011 in 34 European and Australian centers. Mortality rates for patients with and without inhibitors were compared. Results: During 64 200 patient-years of follow-up, 148 patients died (mortality rate, 2.30 per 1000 person-years; 95% confidence interval (CI), 1.96-2.70) at a median age of 64 years (interquartile range [IQR], 49-76). In 62 patients (42%) the cause of death was hemophilia related. Sixteen inhibitor patients died at a median age of 71 years (IQR,. In ten patients the inhibitor was present at time of death; seven of them died of severe bleeding complications. The all-cause mortality rate in inhibitor patients was > 5 times increased compared with that for those without inhibitors (ageadjusted mortality rate ratio, 5.6). Conclusion: Inhibitor development in non-severe hemophilia is associated with increased mortality. High rates of hemophilia-related mortality in this study indicate that non-severe hemophilia is not mild at all and stress the importance of close follow-up for these patients.

To cite this article: Eckhardt CL, van der Bom JG, van der Naald M, Peters M, Kamphuisen PW, Fijnvandraat K. Surgery and inhibitor development in hemophilia A: a systematic review. J Thromb Haemost 2011; 9: 1948-58.Summary. Background: Although the association between intensive treatment and the formation of inhibiting antibodies towards factor VIII (FVIII) in hemophilia A has been demonstrated, the contributing effect of surgery is presently unclear. The release of immunological danger signals resulting from tissue damage during surgery in the presence of a high FVIII antigen load may elicit the formation of FVIII antibodies. The aim of this systematic review was to investigate the role of surgery in the inhibitor risk associated with intensive treatment as compared with treatment for bleeding and prophylactic administration of FVIII. Methods: A comprehensive literature search was performed that identified four cohort studies and three case control studies, comprising 342 inhibitor patients among a total of 957 hemophilia A patients. Results: Intensive treatment increased the inhibitor risk, most pronounced with intensive treatment of ‡ 5 exposure days (EDs) compared with < 3 EDs (OR, 4.1; 95% confidence interval, 2.6-6.5). Pooled odds ratio for inhibitor development in severe hemophilia patients that received intensive treatment for surgery at first exposure was 4.1 (95% confidence interval, 2.0-8.4) compared with treatment for bleeding or prophylaxis. Information on continuous infusion, previously treated patients and non-severe hemophilia A was insufficient for valid meta-analyses. Conclusions: Intensive FVIII treatment for surgery at first exposure leads to a higher inhibitor risk in hemophilia A patients compared with intensive treatment for bleeding.

Background Inhibitor development is a major complication of treatment with factor VIII concentrates in hemophilia. Findings from studies among severe hemophilia A patients suggest that intensive treatment episodes increase the risk of developing inhibitors. Objectives We set out to assess whether intensive treatment is also associated with an increased risk of inhibitor development among non-severe hemophilia A patients. Patients/Methods We performed a nested case-control study. A total of 75 inhibitor patients (cases) and 223 control patients were selected from 2709 non-severe hemophilia A patients (FVIII:C, 2-40%) of the INSIGHT cohort study. Cases and controls were matched for date of birth and cumulative number of exposure days (EDs) to FVIII concentrates. Conditional logistic regression was used to calculate both unadjusted and adjusted odds ratios (aOR); the latter were adjusted for a priori specified confounders. Results Peak treatment of 5 or 10 consecutive EDs did not increase inhibitor risk (aOR, 1.0; 95% confidence interval (CI), 0.4-2.5; and aOR, 1.8; CI, 0.6-5.5, respectively). Both surgical intervention (aOR, 4.2; CI, 1.7-10.3) and a high mean dose (> 45 IU kg /ED) of FVIII concentrate (aOR, 7.5; CI, 1.6-35.6) were associated with an increased inhibitor risk. Conclusions Our findings suggest that high-dose FVIII treatment and surgery increase the risk of inhibitor development in non-severe hemophilia A. Together with the notion that non-severe hemophilia A patients are at a lifelong risk of inhibitor development, we suggest that in the future physicians will review the arguments for the FVIII dose and elective surgery extra critically.

In nonsevere haemophilia A (HA) patients the presence of an inhibitor may exacerbate the bleeding phenotype dramatically. There are very limited data on the optimal therapeutic approach to eradicate inhibitors in these patients. We aimed to describe inhibitor eradication treatment in a large cohort of unselected nonsevere HA patients with inhibitors. We included 101 inhibitor patients from a source population of 2,709 nonsevere HA patients (factor VIII 2-40 IU/dl), treated in Europe and Australia (median age 37 years, interquartile range (IQR) 15-60; median peak titre 7 BU/ml, IQR 2-30). In the majority of the patients (71 %; 72/101) the inhibitor disappeared; either spontaneously (70 %, 51/73) or after eradication treatment (75 %, 21/28). Eradication treatment strategies varied widely, including both immune tolerance induction and immunosuppression. Sustained success (no inhibitor after rechallenge with factor VIII concentrate after inhibitor disappearance) was achieved in 64 % (30/47) of those patients rechallenged with FVIII concentrate. In high-titre inhibitor patients sustained success was associated with eradication treatment (unadjusted relative risk 2.3, 95 % confidence interval 1.3-4.3), compared to no eradication treatment. In conclusion, in nonsevere HA patients most inhibitors disappear spontaneously. However, in 35 % (25/72) of these patients an anamnestic response still can occur when rechallenged, thus disappearance in these patients does not always equal sustained response. Treatment for those requiring eradication has to be decided case by case, as one single approach is unlikely to be appropriate for all.

SummaryInhibitor development is currently the most severe complication in mild/ moderate haemophilia A patients, causing increased bleeding tendency, hospitalization and mortality. It has been suggested that receiving high doses of factor VIII (FVIII) concentrates for surgical procedures is an important risk factor for inhibitor development in these patients. The current multicentre study aimed to determine prospectively the incidence of inhibitor development after intensive FVIII replacement therapy for surgical procedures in patients with mild/moderate haemophilia A. All consecutive patients with mild/moderate haemophilia A were included when they required at least 10 000 iu of FVIII concentrates (or 250 iu/kg) for 5 or more days for a surgical procedure. Potential clinical risk factors for inhibitor development and results of inhibitor tests were collected. Forty-six patients with a median age of 54 years (interquartile range, 40-59 years) were included in the study. F8 genotyping revealed 20 different missense mutations. Patients received either recombinant (65%) or plasma-derived FVIII concentrates (35%) by intermittent bolus injections (41%) or continuous infusion (57%). Two patients developed a low titre inhibitor postoperatively. The incidence of inhibitor development following intensive treatment for surgery in this unselected prospective cohort of mild/moderate haemophilia A patients was 4% (95% confidence interval, 0·5-14·8).

Background Non-severe hemophilia (factor VIII concentration [FVIII:C] of 2-40 IU dL ) is characterized by a milder bleeding phenotype than severe hemophilia A. However, some patients with non-severe hemophilia A suffer from severe bleeding complications that may result in death. Data on bleeding-related causes of death, such as fatal intracranial bleeding, in non-severe patients are scarce. Such data may provide new insights into areas of care that can be improved. Aims To describe mortality rates, risk factors and comorbidities associated with fatal intracranial bleeding in non-severe hemophilia A patients. Methods We analyzed data from the INSIGHT study, an international cohort study of all non-severe hemophilia A patients treated with FVIII concentrates during the observation period between 1980 and 2010 in 34 participating centers across Europe and Australia. Clinical data and vital status were collected from 2709 patients. We report the standardized mortality rate for patients who suffered from fatal intracranial bleeding, using a general European male population as a control population. Results Twelve per cent of the 148 deceased patients in our cohort of 2709 patients died from intracranial bleeding. The mortality rate between 1996 and 2010 for all ages was 3.5-fold higher than that in the general population (95% confidence interval [CI] 2.0-5.8). Patients who died from intracranial bleeding mostly presented with mild hemophilia without clear comorbidities. Conclusion Non-severe hemophilia A patients have an increased risk of dying from intracranial bleeding in comparison with the general population. This demonstrates the need for specialized care for non-severe hemophilia A patients.