Parts Of The Country Clinical Characteristics Of Patients With Hemophilia A, Clotting Factor Viii Inhibitor Screening And Methods Comparison

Background:Hemophilia A(HA) is a recessive,X chromosome-linked hereditary bleeding disorder.The patients have unusual bleeding symptoms early in life related to deficiency of factorⅧ(FⅧ).The clinical hallmarks of HA are joint and muscle hemorrhages,and potentially fatal hemorrhages.In developed countries hemophiliacs are allowed to have a quality and expectancy of life very similar to those seen in the general population due to accurate diagnosis and sustained replacement therapy. Recently,the phenotypic heterogeneity and FⅧinhibitor development in the patients with HA have been well investigated in the developed countries.China is a developing country,and more efforts are needed to diminish the gap between our country and developed countries in hemophiliac diagnosis,clinical care and scientific research.In this study,we have analyzed the clinical features and phenotypic heterogeneity,investigated the frequency of FⅧinhibitors and related risk factors and explored concordance between two FⅧinhibitor assays among the patients with HA from the Northern China.Objective:1.To analyze clinical features of HA and the reasons for phenotypic heterogeneity.2.To study the positive rate of FⅧinhibitors and the risk factors for the development of the inhibitors.3.To compare the Bethesda assay and the Nijmegen assay in the inhibitor detection.Methods:1.Clinical data and blood samples were collected from the HA patients in Beijing, Henan,Hebei,Shanxi,Shaanxi and Xinjiang.2.FⅧ:concentration(FⅧ:C) was measured using one-stage coagulation assay; the antigen of von Willbrand Factor(vWF:Ag) determined by ELISA;FⅧinhibitors titred by the Bethesda assay and the Nijmegen assay;AntithrombinⅢ(ATⅢ) activity and Protein C(PC) activity detected by colorimetric assay;Protein S (PS) activity and Activated Protein C Resistance(APC-R) detected by clotting assay. The samples for detection of HCV,HBV and HIV were sent to and measured by Shanghai Ruijin Hospital.3.Clinical and laboratory data was analyzed by SPSS16.0 software,and P＜0.05 was considered to indicate statistical significance.Results:1.Clinical features of HA patients:388 hereditary HA patients were recruited.The median age of patients was 19 years,with 83.5%with moderate disease.18.3%of 355 patients were diagnosed after two years of their first episode of bleeding,and 54.2% of 367 patients had no family history of a bleeding disorder.Among 362 patients, 38.5%had developed joint deformities within ten years old,and more than 90% patients had joint deformities after the second decade.88.8%of 305 patients had received replacement therapy including FⅧconcentrates.The median age of patients first exposed to FⅧproducts was 11 years.47.9%of 213 patients had HCV infection,1.8%of 164 patients had HBV infection,and none of 164 patients had HIV infection.2.The reasons for phenotypic heterogeneity in HA:50 patients(FⅧ:C 1-2%) were divided into mild bleeding group(＜6 bleeds per year) and severe bleeding group(＞12 bleeds per year).No deficient PC and ATⅢactivity and positive APC-R were found.There were 3 patients with lower PS activity in each group.3.The positive rate and the risk factors for development of FⅧinhibitors:6.2% patients had FⅧinhibitors using the Nijmegen assay,and 83.3%were low responders(titers less than 5BU).The median age was 24 years.No patients had the inhibitors among 32 with mild HA,and 19 patients had the inhibitors among 324 with moderate HA(5.9%),and 5 patients had the inhibitors among 32 with severe HA (15.6%).There was significant difference among three groups according to the fisher test(P=0.042).Among 76 HA patients with intensive exposure to FⅧ(more than 5 successive exposure days),13(17.1%) had inhibitors.However,only 9 of 184(4.9%) patients without intensive exposure had inhibitors.The positive rate of the inhibitors had significant difference between two groups according to the Chi-Square test (P=0.001).The inhibitor was found in 11 of 102(10.8%) patients with HCV infection and 2 of 111(1.8%) patients without HCV infection,respectively(P=0.006,according to Chi-Square test).4.Concordance between two FⅧinhibitor assays:Among 237 HA patients,the positive rate of FⅧinhibitor was 5.5%by the Bethesda assay and 8.4%by the Nijmegen assay(P=0.065,according to McNemar exact test).Conclusions:1.There are differences in clinical features of HA patients between China and developed countries.The ratio of patients with no family history,the rates of joint deformities and HCV infection in our patients are higher than those in developed countries.More patients have experience of misdiagnosis and inaccurate treatment inclusive of replacement therapy.2.It seems that the defect anticoagulant proteins and APC-R are not related to the frequency and severity of hemorrhage in HA patients.3.The positive rate of FⅧinhibitor is lower.Most of the cases are low responders and the ages are older than those reported in developed countries.The HA severity, intensive exposure to FⅧconcentrates and HCV infection are associated with development of the inhibitors.4.No differences in detecting FⅧinhibitor between the Bethesda assay and the Nijmegen assay.It seems the Nijmegen assay may be sensitive to low titer inhibitors.