title: Frequency of factor VIII (FVIII) inhibitor in haemophilia A.
abstract: OBJECTIVE
  To determine the frequency of factor VIII specific inhibitors in haemophilia A.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  National Institute of Blood Disease and Bone Marrow Transplantation, Karachi, from August 2007 to March 2009.
  
  
  METHODS
  Venous blood samples of diagnosed haemophilia A patients were collected in tubes containing 0.109 M (3.2%) trisodium citrate, centrifuged without delay at 1200 G for 15 minutes. Factor VIII inhibitors were screened by APTT based method using 50:50 patients' plasma mixed with normal plasma incubated together for 2 hours at 37°C. Quantitative assay was carried out to measure Bethesda units (BU). Samples were labelled as low titre inhibitor when less than 5 BU detected, while high titre inhibitor when more than 5 BU were detected.
  
  
  RESULTS
  A total of 140 Haemophilia A patients were evaluated for allo-antibodies who received treatment with FVIII concentrates / FFP/ cryoprecipitate. Among them 21 patients (15%) were found to have positive screening test results for inhibitors. The mean age of patients with inhibitors was 11.9 + 8.81 years. Thirteen were high responders (62%) while 8 were low responders (38%). The mean inhibitor level in low (titre) responders was 2.46 + 1.31 BU while in high (titre) responders it was 29.15 + 12.81 BU. According to severity of the disease 12/21 with severe haemophilia A (57.2%) developed inhibitors, whereas 8/21 with moderate (38%) and 1/21 with mild haemophilia A (4.7%) showed positive results for inhibitors.
  
  
  CONCLUSIONS
  Fifteen percent haemophilia A patients developed inhibitors in this cohort, majority with severe and moderate haemophilia A. Age and severity of disease were found to be main contributing factors in patients who developed inhibitors.
authors.affiliation: Department of Haemostasis and Thrombosis, National Institute of Blood Disease & Bone Marrow Transplantation, Karachi. drmunirashoaib@yahoo.com
authors.forename: Munira
authors.initials: M
authors.lastname: Borhany
authors.forename: Meena
authors.initials: M
authors.lastname: Kumari
authors.forename: Tahir
authors.initials: T
authors.lastname: Shamsi
authors.forename: Arshi
authors.initials: A
authors.lastname: Naz
authors.forename: Tasneem
authors.initials: T
authors.lastname: Farzana
mesh_terms: D000293:Adolescent; D000328:Adult; D019774:Blood Coagulation Factor Inhibitors / Q000097:blood*; D016913:Blood Component Transfusion / Q000379:methods*; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005169:Factor VIII / Q000378:metabolism / Q000627:therapeutic use*; D005500:Follow-Up Studies; D006467:Hemophilia A / Q000097:blood* / Q000401:mortality / Q000628:therapy*; D006801:Humans; D007108:Immune Tolerance; D007223:Infant; D007518:Isoantibodies / Q000097:blood*; D008297:Male; D010949:Plasma; D018570:Risk Assessment; D012720:Severity of Illness Index; D015996:Survival Rate; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D019774:Blood Coagulation Factor Inhibitors; D007518:Isoantibodies; D005169:Factor VIII