Non-severe Haemophilia Research Articles

A large-scale computational study of inhibitor risk in non-severe haemophilia A.

Over 500 missense F8 mutations have been reported to cause non-severe haemophilia A. Some F8 genotypes appear to confer a higher risk of inhibitor formation than others and individuals with the same F8 genotype may have differing risks of inhibitor formation. We present an in silico strategy demonstrating the heterogeneity of factor VIII (FVIII)-derived antigen presentation whilst identifying patterns of human leucocyte antigen (HLA) peptide binding that might predict future inhibitor risk. A well-validated computational tool, NetMHCII, enabled large-scale comparison of predicted antigen presentation between endogenous, mutated FVIII-derived peptides and wild-type, therapeutic FVIII-derived peptides spanning all F8 missense mutation positions reported to The Haemophilia A Mutation, Structure and Resource Site (HADB). We identify 40 F8 genotypes to be 'low risk' at a 50% inhibitory concentration (IC50 )-binding threshold of 300nmol/l (P=0·00005), defined as absence of novel peptide-major histocompatibility complex (MHC) surfaces for all 14 common HLA-DR alleles assessed. Analysing each of the possible 7280 F8 genotype/HLA-DR permutations individually at an IC50 threshold of 300nmol/l, 65% are predicted to not generate a novel peptide-MHC surface that would be necessary to engage T cell help for subsequent anti-FVIII antibody generation. This study demonstrates the future importance of interpreting F8 genotype in the context of an individual's HLA profile to personalize inhibitor risk prediction.

Risk assessment for coronary heart disease in patients with haemophilia: a single centre study in the United States.

In haemophilia, coronary heart disease (CHD) occurs at a similar frequency as in the general population, but the contributing risk factors in haemophilia are incompletely understood. To investigate risk factors and 10-year CHD risk in a single centre cohort of patients with haemophilia (PWH) ≥20years old (n=89). We retrospectively applied the modified Framingham National Cholesterol Education Program/Adult Treatment Panel (NCEP/ATP) III risk prediction equation. Three risk levels were defined: <10% (low), 10-20% (intermediate) and >20% (high). Results were compared to the National Health and Nutrition Examination Survey (NHANES). Mean age in both cohorts was similar. Compared to NHANES, systolic blood pressures were significantly higher in PWH, but current smoking and cholesterol were lower. CHD risk differed significantly between PWH and NHANES (P=0.005) with a higher proportion of PWH classified at low risk (77.5% vs. 61.0%). The proportion of low risk patients was also significantly higher for severe haemophilia patients compared to non-severe haemophilia patients (88.6% vs. 66.7%, P=0.02). Among PWH, and compared to PWH who were hepatitis C (HepC) negative, HepC positive patients had significantly lower cholesterol, LDL and triglycerides. The CHD risk of HepC positive patients differed significantly from NHANES (P=0.03) with a lower proportion of HepC positives being classified as high risk (5.7% vs. 17.3%). Favourable CHD risk classification in PWH may be influenced by low cholesterol associated with HepC infection. Estimates of CHD risk in PWH by composite scoring may not be accurate and will require studies correlating risk factors with incident CHD.

Rituximab as first‐line treatment for the management of adult patients with non‐severe hemophilia A and inhibitors

The role of immunosuppression in the management of patients with congenital hemophilia and inhibitors is uncertain. The use of rituximab has been limited to case reports and case series. In most reports, rituximab was used as second-line or third-line treatment following failure of conventional immune tolerance induction therapy, and more commonly in pediatric patients. The objective of this study was to describe our experience with rituximab for the eradication of factor VIII inhibitors in adult patients with non-severe hemophilia A. We retrospectively reviewed the medical records of adult patients with non-severe hemophilia A and a diagnosis of FVIII inhibitor treated with rituximab (four weekly doses of 375 mg m(-2) ) as first-line treatment at our hemophilia center. We identified nine consecutive adult patients with hemophilia A (moderate, n = 5; mild, n = 4) at our institution between 2000 and 2013, with a median age of 54 years (range, 24-77 years) at the time of inhibitor diagnosis. No patient received concomitant immune tolerance induction therapy. All nine patients had successful eradication of FVIII inhibitors. The median time from the first dose of rituximab to a clinical response was 95 days (range, 12-278 days). The median follow-up was 56 months (range, 13-139 months). Following inhibitor eradication, eight patients were rechallenged with FVIII concentrates. Two patients developed inhibitor recurrence associated with surgery. This case series demonstrates that rituximab is a useful first-line treatment to achieve sustained inhibitor eradication in adult patients with non-severe hemophilia A.

Abstracts of the WFH 2014 World Congress, May 11-15, 2014, Melbourne, Australia.

Introduction and Objectives: Inhibitor development in nonsevere haemophilia A patients (FVIII:C, 2-40 IU/dL) has a heterogeneous clinical phenotype, ranging from irrelevant transient inhibitors to high titre neutralizing antibodies with severe bleeding complications. Data on inhibitor presentation are scarce and selected, favouring those with severe complications. The aim of current study was to describe the presenting symptoms of inhibitors in a large unselected cohort of nonsevere haemophilia patients. Materials and Methods: Clinical data were collected of 107 inhibitor patients derived from a source population of 2,709 nonsevere haemophilia A patients that were treated between 1980 and 2011 in 34 European and Australian centers (the INSIGHT consortium). Patients were subdivided according to age and calendar period at time of inhibitor development (10-year groups), aiming to search for age-related trends and trends over time. Results: Age at inhibitor detection varied widely between 1 and 85 years with a median age of 38 years (IQR, 15-61). Most inhibitors developed in the period of 2000-2010 (n = 64, 60%). Inhibitors developed after a median of 28 exposure days (IQR, 14-66), which was comparable between all age groups. Fifty-seven patients (56%) had high titre inhibitors (>5 BU/mL). About half of the high titre inhibitors developed in patients older than 40 years (n = 30, 53%) and 60% after the year 2000 (n = 34). In 13 (12%) inhibitor patients the inhibitor was detected during routine laboratory screening and no clinical signs of the inhibitor were present. More than half of the patients (n = 61) had an increased bleeding tendency at presentation with inhibitor. In 80 patients (80%) endogenous FVIII:C was decreased to below 5 IU/dL (including 33/44 patients with low titer inhibitors), of whom FVIII:C fell below ≤ 0.01 IU/mL in 49 patients (46%). Conclusion: Half of the patients with nonsevere haemophilia A and inhibitors developed high titre inhibitors; these were more common in the last decennium. More than half of the patients presented with bleeding complications and 46% had changed to a severe phenotype. These results stress the importance of close follow-up after exposure to therapeutic factor VIII concentrates in nonsevere haemophilia A patients.

Haemophilia A mutations in patients with non-severe phenotype associated with a discrepancy between one-stage and chromogenic factor VIII activity assays

About one-third of patients with non-severe haemophilia A (HA) show a discrepancy of factor (F)VIII activity (FVIII:C) measured by one-stage (FVIII:C1st), two-stage assays or the chromogenic method (FVIII:Cchr). The aim of the study was to characterise the mutation profile in patients with FVIII:C assay discrepancies. FVIII:C discrepancy was considered significant if the calculated ratio between FVIII:C1st and FVIII:Cchr was ≤ 0.6. In 16 patients FVIII:C1st was higher than FVIII:Cchr. The reversephenomenon was observed in 83 patients. Genetic analysis revealed 23 different missense mutations of which 17 were novel. Most mutations, exhibiting a higher FVIII:C1st were localised in the A1-A2-A3 interface. The majority of mutations associated with FVIII:Cchr>FVIII:C1st discrepancy were located close to or within the thrombin cleavage sites, FIX or vWF binding sites. Our data show a correlation between FVIII:C and thrombin generation testing with a clear differentiation between patients with haemophilia and normal controls. However, in the subgroup of FVIII:C1st>FVIII:Cchr discrepancy, the endogenous thrombin potential and peak thrombin parameters were similar to non-discrepant haemophilia patients, while in the inverse discrepancy FVIII:Cchr>FVIII:C1st, these variables showed values close to that of the normal control group. Certain hereditary F8 missense mutations cause discrepancy in FVIII:C as measured with different assays. This can lead to failure in diagnosing HA or incorrectly classifying the severity of the disease. Therefore, we recommend that initial diagnosis of non-severe HA phenotypes should be based on results of both FVIII:C1st and FVIII:Cchr assays.

The role of disease severity in influencing body mass index in people with haemophilia: a single‐institutional cross‐sectional study

The aim of this study was to evaluate the effect of haemophilia disease severity and potential intermediaries on body mass index (BMI) in patients with haemophilia. A secondary analysis of a cross-sectional study of 88 adults with haemophilia was undertaken. On bivariate analysis, persons with severe haemophilia had 9.8% lower BMI (95% CI -17.1, -3.0) than persons with non-severe haemophilia. The effect of haemophilia severity on BMI varied significantly by human immunodeficiency virus (HIV) status. Among HIV-positive subjects, haemophilia severity was not associated with BMI (+5.0%, 95% CI -22.4, 41.9). Among HIV-negative subjects, severe haemophilia was associated with 15.1% lower BMI (95% CI, -23.6, -5.7). Older (>41 years) HIV-negative subjects with severe haemophilia had a BMI that was 24.8% lower (95% CI -39.1, -7.0) than those with non-severe haemophilia. No statistically significant association was detected between BMI and severe vs. non-severe haemophilia for younger HIV-negative subjects. Although joint disease, as measured by the World Federation of Hemophilia (WFH) joint score, did not influence the association between haemophilia disease severity and BMI, adjustment for the atrophy component of the WFH score reduced the association between haemophilia severity and BMI by 39.1-69.9%. This suggested that muscle atrophy mediated at least part of the relationship between haemophilia severity and BMI. Haemophilia disease severity is associated with BMI and appears to be mediated by muscle atrophy of surrounding joints. This association appears to be modified by HIV status and possibly age.

Factor VIII gene (F8) mutation and risk of inhibitor development in nonsevere hemophilia A

AbstractNeutralizing 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 Kaplan-Meier 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, 12-71). 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.

Arthropathy in Patients with Moderate Hemophilia A: A Systematic Review of the Literature

Chronic arthropathy is a major complication in severe hemophilia A (Factor [F] VIII < 1%). Almost all adults with severe hemophilia, who have not received prophylaxis with FVIII since their early childhood, suffer from chronic arthropathy. Patients with moderate hemophilia (FVIII activity 1-5%) usually experience fewer joint bleeds than those with severe hemophilia and are thought to rarely develop a significant degree of chronic arthropathy. However, some patients with moderate hemophilia behave like those with the severe form of the disorder, reporting several joint bleeds per year and significant joint impairment. Currently, only little data are available about the prevalence of arthropathy, the degree of quality of life impairment, and the need for orthopedic care/aids in patients with moderate hemophilia. In this systematic review of literature, the prevalence of overt arthropathy ranges between 15 and 77% in patients with moderate hemophilia and prophylactic replacement treatment is prescribed in approximately 30% of these patients, usually after diagnosis of clinically overt arthropathy. Moreover, because of the lack of imaging studies (magnetic resonance and/or ultrasound), the prevalence of subclinical arthropathy cannot be determined. These data confirm that severity of hemophilia should not be defined only according to FVIII levels and that a relevant proportion of patients with nonsevere hemophilia might benefit from a "tailored early prophylaxis."

Identification of 18 High Risk F8 Mutations for Inhibitor Development in 2,700 Non-Severe Hemophilia A Patients

Identification of 18 High Risk F8 Mutations for Inhibitor Development in 2,700 Non-Severe Hemophilia A Patients

Eradication of factor viii inhibitors in patients with mild and moderate hemophilia A

In hemophilia A, up to 25% of new antifactor VIII (FVIII) inhibitory antibodies (inhibitors) occur in patients with mild or moderate disease. Once the inhibitor develops, options for management include observation, immune modulation, and immune tolerance induction (ITI). Currently, there is little data to guide a clinician's management decisions. In a case series, eight of the 26 subjects with mild or moderate hemophilia complicated by an inhibitor underwent ITI; two were successful, two were unsuccessful, and four were partially successful. In a systematic review of the literature, 12 of the 16 patients with mild or moderate hemophilia responded to rituximab for treatment to eradicate the inhibitor. To increase our understanding of treatment options for inhibitor eradication in patients with mild or moderate hemophilia A complicated by an inhibitor, a secondary analysis of clinical and treatment characteristics in a cohort of 36 patients with mild or moderate hemophilia A and inhibitor was undertaken. In multivariate analyses, rituximab alone (n = 6) and other immune-modulating treatments alone (n = 2) were significantly associated with an increased likelihood of inhibitor clearance [hazard ratio (HR) = 4.4 (95% CI = 1.06–20.03) and 10.21 (95% CI = 1.17–78.28), respectively], whereas ITI alone (n = 9) was not [HR = 1.35 (95% CI = 0.44–4.07)].

Abstracts

Introduction: Inhibitor development is a major complication of the treatment with factor VIII (FVIII) concentrates in patients with non-severe hemophilia A. Current hypothesis suggest that the mutation in the FVIII gene (F8) is an important predictor of inhibitor risk in these patients, however identification of high-risk patients is limited by the absence of absolute inhibitor risk of individual F8 mutations. The aim of this study was to assess inhibitor risk of F8 mutations in a large unselected cohort of non-severe hemophilia A patients. Methods: The INSIGHT cohort included 2,711 non-severe hemophilia A patients (FVIII 2-40%) who were treated with FVIII concentrates between 1980 and 2011 in 34 centres in Europe and Australia. Absolute inhibitor risk of F8 mutations was assessed in 1,112 patients located in 14 centres in which genotyping was universally performed; these were calculated as cumulative Kaplan-Meier incidences with inhibitor as the event and cumulative number of exposure days (ED) as time variable. Results: During 117,700 ED, 109 patients developed an inhibitor (absolute risk, 8.9%, 95% CI 7.1-10.6) after a median of 28 ED (IQR 14-68). F8 genotype was available in 898 patients (81%) among whom 236 different F8 mutations were identified. Eighteen mutations (L412F, R531C, R593C, P1761Q, F1775V, R1781G, P1854L, R1997W, D2074G, F2101C, Y2105C, R2150H, R2159C, E2228D, W2229C, V2232A, H2309D, Stop2333C) were classified as high risk mutation (n=274 patients; 50 inhibitors) with absolute inhibitor risks between 7 and 100%, the other 218 mutations were classified as low-risk mutation (absolute risk

Non-fatal cardiovascular disease, malignancies, and other co-morbidity in adult haemophilia patients

IntroductionWith increasing life expectancy, more haemophilia patients will be confronted with age-related problems. To ensure optimal care, it is important to know the occurrence of both fatal and non-fatal cardiovascular disease, malignancies and other types of co-morbidity in these patients. Our aim was to retrospectively assess the occurrence of co-morbidity and causes of death in a substantial birth-cohort of haemophilia patients. MethodsData on all types of co-morbidity were collected from medical records of 408 haemophilia patients (204 severe, 204 non-severe) born before 1971, and compared with the Dutch age-matched general male population. ResultsTen patients had 11 myocardial infarctions, none of which were fatal. The cumulative incidence of non-fatal myocardial infarction was significantly lower in patients with severe haemophilia than in the general population (0.5% versus 4.8%), but was not decreased in patients with non-severe haemophilia (4.4%). Intracranial bleeding occurred significantly more often in haemophilia patients. The occurrence of non-virus related malignancies, and other non-virus related co-morbidities was similar in haemophilia patients and the general population. HIV infection was present in 12% of patients, and hepatitis C infection in 56%. Seventy-eight patients (19%) were deceased. Main causes of death were malignancies, AIDS, hepatitis C, and intracranial bleeding. ConclusionsOur results showed a decreased occurrence of myocardial infarction in patients with severe haemophilia, suggesting a protective effect of very low clotting factor levels on thrombotic cardiac events. No differences were found between haemophilia patients and the general population in the occurrence of any other type of non-virus related co-morbidity.

Surgery and inhibitor development in hemophilia A: a systematic review.

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. 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. 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. Intensive FVIII treatment for surgery at first exposure leads to a higher inhibitor risk in hemophilia A patients compared with intensive treatment for bleeding.

Clinical severity of haemophilia A: does the classification of the 1950s still stand?

The classification of haemophilia originates from 1950s and has been adopted unchallengedly by the ISTH in 2001. The aim of this study was: does the current classification compare onset of bleeding and age at first treatment, as well as annual joint bleeding frequency according to baseline FVIII activity? Data on age and reason of diagnosis, onset of treatment, onset of bleeding and bleeding frequency from 411 patients with haemophilia A born after 1970 were collected. Data were analysed according to base-line FVIII activity levels. Age at diagnosis, onset of bleeding and start of treatment according to FVIII activity were compared with the current classification. Overall, the distinction between severe and non-severe haemophilia was clear. The distinction between mild and moderate haemophilia was more difficult, mostly due to the wide variability in the group of patients with moderate haemophilia. Patients with severe haemophilia experienced their milestones like diagnosis, first treatment and joint bleed earliest, mostly as infants aged 0-3 years, whereas patients with moderate haemophilia reached these milestones around toddler age, 2-7 years, and patients with mild haemophilia reached them when they were in elementary school, around the ages of 5-14 years. This study confirms the clinical distinction between severe and non-severe haemophilia A. However, the group of moderate haemophilia patients showed a wide variability, warranting close follow-up and individualized treatment.

Habitual physical activity in Dutch children and adolescents with haemophilia

For patients with haemophilia, a physically active lifestyle is important to maintain musculoskeletal health and to prevent chronic diseases, such as cardiovascular disease. Therefore, we studied physical activity levels, in Dutch children and adolescents with haemophilia as well as its association with aerobic fitness and joint health. Forty-seven boys with haemophilia (aged 8-18) participated. Physical activity was measured using the Modifiable Activity Questionnaire (MAQ) and was compared with the general population. Aerobic fitness was determined using peak oxygen uptake (VO(₂peak)). Joint health was measured using the Haemophilia Joint Health Score (HJHS). Associations between physical activity, joint health and aerobic fitness were evaluated by correlation analysis. Subjects were 12.5 (SD 2.9) years old, had a Body Mass Index (BMI) of 19.5 (SD 3.1; z-score 0.5) and a median HJHS score of 0 (range 0-6). Cycling, physical education and swimming were most frequently reported (86%, 69% and 50% respectively). Children with severe haemophilia participated significantly less in competitive soccer and more in swimming than children with non-severe haemophilia. Physical activity levels were similar across haemophilia severities and comparable to the general population. VO(₂peak) kg⁻¹ was slightly lower than healthy boys (42.9 ± 8.6 vs. 46.9 ± 1.9 mL kg⁻¹ min⁻¹; P = 0.03). Joint health, aerobic fitness and physical activity showed no correlation. Dutch children with haemophilia engaged in a wide range of activities of different intensities and showed comparable levels of physical activity to the general population. Aerobic fitness was well preserved and showed no associations with physical activity levels or joint health.

Protected by Nature: Effects of Exercise In Non-Severe Haemophilia Patients

AbstractAbstract 545 Background:An increase of clotting factor VIII (FVIII) within 10 minutes after physical exercise has been reported in healthy subjects and patients with von Willebrand disease. The mechanism of FVIII increase through exercise is thought to be similar to that of desmopressin, which increases FVIII. Therefore, moderate and mild haemophilia A patients should also be able to increase their endogenous FVIII levels after exercise. A proof of principle study was performed to test this hypothesis. Methods:Changes in coagulation associated with exercise of 15 haemophilia A patients, aged 20–39 years, were measured. Eight had moderate haemophilia (FVIII 1–5 IU/dl), 7 had mild haemophilia with endogenous FVIII activity levels at the lower end of the range (FVIII 6–16 IU/dl) Patients were encouraged to cycle until volitional exhaustion, on an electronically braked cycle ergometer. Blood samples were drawn before and 10 minutes after the incremental exercise test. Blood was frozen and analyzed for FVIII, von Willebrand factor (vWF) and von Willebrand propeptide (vWpr), in one batch to avoid inter-assay variation. In mild haemophilia patients, changes in coagulation profile were compared to DDAVP tolerance tests. Results:All 15 patients had an increased FVIII level after exercise. Median relative increase was 2.5 times (interquartile range (IQR)= 1.2–4.0). The relative increase did not vary across severities (median relative increase of FVIII was 2.4 times (IQR= 1.3–4.0) for moderate haemophilia patients compared to median 2.5 times (IQR=1.2-4.0) in patients with mild haemophilia Mann-Whitney: p =0.91). However, the absolute FVIII levels were very different with a median FVIII level of only 9 IU/dl; IQR= 8–11 IU/dl) in patients with moderate haemophilia, compared with a much higher median FVIII level of 21 IU/dl; IQR=19-44 IU/dl) attained in patients with mild haemophilia. vWF and vWFpr also increased independent of severity (p=0.3-0.6) in all patients, median 50%; IQR 30–79% for vWF and median 165%; IQR 130–244% for vWFpr, reflecting acute release of coagulation factors. DDAVP response tests were available only for patients with mild haemophilia. Relative increase after DDAVP administration was median 3.5 times (IQR= 2.5–4.5), similar to increase in FVIII after exercise (Wilcoxon: p=0.14). Conclusion:Although normal levels were not achieved, the increase of FVIII activity during exercise may reduce bleeding risk and therefore help promote participation in sports and other strenuous activities for moderate and mild haemophilia A patients with modest endogenous FVIII activities who might be considered at high bleeding risk. [Display omitted] Disclosures:No relevant conflicts of interest to declare.

Measurement of alloantibodies against FVIII in patients with hemophilia A using a newly-developed ELISA and its clinical application

Objective An ELISA-based assay for detecting alloantibodies against FⅧ was established to estimate the incidence of alloantibodies against FⅧ in treated patients with hemophilia A. Methods One hundred and forty patients with hemophilia A and 80 healthy controls were enrolled. Among hemophilia A patients, 84, 34 and 22 patients were in severe, moderate and mild conditions respectively. All patients were treated with plasma-derived FⅧ concentrates before. The titer wells were coated with MoAb against FⅧ which was developed in our laboratory. Then human recombinant FⅧ concentrates were applied. After incubation in room temperature for 2 hours, diluted plasma samples and HRP-conjugated goat anti-human IgG were added successively. Finally Absorbance (A490) were measured and recorded. Inhibitor activity against FⅧ for all plasma samples was measured by a modified Nijmegen assay simultaneously. Results The results showed that alloantibodies against FⅧ were found in 40.0% (56/140) patients by ELISA. And the alloantibody incidences in the severe and non-severe patients were 47.6% (40/84) and 28.5% (16/56)respectively. There was statistical significance between these two categories (x2 = 5.079, P ＜ 0.05 ). The FⅧ inhibitor activity was detected in 24.3% (34/140) patients by modified Nijmegen assay. The inhibitor incidences in the severe and non-severe patients were 33.3% (28/84) and 10.7% (6/56) respectively.There was statistical significance (x2 = 9.349, P ＜ 0.05). Twenty-five patients were positive for FⅧ alloantibodies by ELISA but had no FⅧ inhibitor activity by the modified Nijmegen assay. The positive rates of FⅧ alloantibodies and inhibitor activity were 40.0% (56/140) and 24.3% (34/140) respectively,which had significant difference (x2 = 15.75, P ＜ 0.01 ) and strong positive correlation ( rn = 0.59, P ＜0.01 ). Meanwhile the results deduced from these two tests shared a high consistency rate ( Kappa = 0.55,P ＜0.01 ). Conclusions The detection rate for alloantibodies against F Ⅷ is enhanced by our newlydeveloped ELISA. Our results suggest that the occurrence of the alloantibodies against F Ⅷ in Chinese hemophilia A patients is not rare and the alloantibody incidence is preponderant in the patients with severe hemophilia A compared with non-severe hemophilia A patients. Key words: Hemophilia A; Factor Ⅷ; Isoantibodies; Enzyme-linked immunosorbent assay

In non-severe hemophilia A the risk of inhibitor after intensive factor treatment is greater in older patients: a case-control study.

Twenty-five percent of new anti-factor VIII (FVIII) antibodies (inhibitors) that complicate hemophilia A occur in those with mild and moderate disease. Although intensive FVIII treatment has long been considered a risk factor for inhibitor development in those with non-severe disease, its strength of association and the influence of other factors have remained undefined. To evaluate risk factors for inhibitor development in patients with non-severe hemophilia A. Information on clinical and demographic variables and FVIII genotype was collected on 36 subjects with mild or moderate hemophilia A and an inhibitor and 62 controls also with mild or moderate hemophilia A but without an inhibitor. Treatment with FVIII for six or more consecutive days during the prior year was more strongly associated with inhibitor development in those ≥30years of age compared with those <30years of age [adjusted odds ratio (OR) 12.62; 95% confidence interval (CI), 2.76-57.81 vs. OR 2.54; 95% CI, 0.61-10.68]. Having previously received <50days of FVIII was also not statistically associated with inhibitor development on univariate or multivariate analysis. These findings suggest that inhibitor development in mild and moderate hemophilia A varies with age, but does not vary significantly with lifetime FVIII exposure days: two features distinct from severe hemophilia A.

In non-severe hemophilia A the risk of inhibitor after intensive factor treatment is greater in older patients: a case-control study: Inhibitors in mild and moderate hemophilia A

In non-severe hemophilia A the risk of inhibitor after intensive factor treatment is greater in older patients: a case-control study: Inhibitors in mild and moderate hemophilia A

Discrepancy between one-stage and chromogenic factor VIII activity assay results can lead to misdiagnosis of haemophilia A phenotype

Severity of bleeding phenotype in hemophilia A (HA) depends on the underlying mutation in the F8 gene and, ultimately, on the concentration and functional integrity of the factor VIII (FVIII) protein in circulating plasma. Initial diagnosis for HA and monitoring of treatment is typically performed by measuring of FVIII activity by either one-stage assay or chromogenic assay. We review evidence for why both types of assay do not give comparable results in a significant proportion of patients with non-severe haemophilia A and why the discrepancy in results between both methods segregates with distinct subclasses of known missense mutations causing haemophilia A. The current understanding of the mechanistic basis for how FVIII:C assay discrepancies arise are discussed. We propose that both methods should be used in initial patient diagnosis along with follow-up genetic analysis to avoid potential misdiagnosis and to optimize treatment monitoring of patients with HA phenotypes.