title: Specific and global coagulation tests in patients with mild haemophilia A with a double mutation (Glu113Asp, Arg593Cys).
abstract: BACKGROUND
  Heterogeneous bleeding phenotypes are observed in haemophilia A patients with the same mutation in the F8 gene. Specific mutations in the A2 domain of factor VIII are associated with mild haemophilia and a higher risk of inhibitor development. Double mutations in mild haemophilia A are rarely reported. In this study, we investigated the in vitro function of factor VIII, performing different specific and global coagulation assays, observed clinical characteristics and assessed the possible predictive diagnostic value of the differences.
  
  
  METHODS
  The clinical features of haemophiliacs with a mild phenotype were reviewed. Blood samples were obtained and analysed for mutations and coagulation assays: activated partial thromboplastin time, one-stage and chromogenic factor VIII activity, factor VIII antigen and rotational thromboelastometry.
  
  
  RESULTS
  We report on a cohort of 22 patients with double Glu113Asp, Arg593Cys mutations. All our patients have a quantitative defect of factor VIII and preserved similar functional activity. Factor VIII activities measured by the one-stage or chromogenic method were not discrepant, although the chromogenic assay resulted in 20% lower factor VIII activities. Waveform analysis showed a lower maximum value of the second derivative curve (Max2) of APTT with curve shape alternation, while thromboelastometry (INTEM) showed low sensitivity in comparison to results in a normal population.
  
  
  CONCLUSIONS
  In genotyping, the coexistence of a second mutation should never be excluded, especially in cases of discordant clinical presentation. Waveform analysis correlates better with factor VIII activity than thromboelastometry and the Max2 parameter could provide additional information in managing haemophilia patients. The utility of specific factor activity and global haemostatic assays in general practice still needs to be investigated.
authors.affiliation: Unit for Special Laboratory Diagnostics, University Children's Hospital, University Medical Centre Ljubljana, Ljubljana, Slovenia.
authors.forename: Alenka
authors.initials: A
authors.lastname: Trampuš Bakija
authors.affiliation: Unit for Special Laboratory Diagnostics, University Children's Hospital, University Medical Centre Ljubljana, Ljubljana, Slovenia.
authors.forename: Maruša
authors.initials: M
authors.lastname: Debeljak
authors.affiliation: Department of Haematology, University Medical Centre Ljubljana, Ljubljana, Slovenia.
authors.forename: Irena
authors.initials: I
authors.lastname: Preložnik Zupan
authors.affiliation: Unit for Haematology and Oncology, University Children's Hospital, University Medical Centre Ljubljana, Ljubljana, Slovenia.
authors.forename: Majda
authors.initials: M
authors.lastname: Benedik Dolničar
authors.affiliation: Unit for Special Laboratory Diagnostics, University Children's Hospital, University Medical Centre Ljubljana, Ljubljana, Slovenia.
authors.forename: Jernej
authors.initials: J
authors.lastname: Kovač
authors.affiliation: Unit for Haematology and Oncology, University Children's Hospital, University Medical Centre Ljubljana, Ljubljana, Slovenia.
authors.forename: Janez
authors.initials: J
authors.lastname: Jazbec
mesh_terms: D000293:Adolescent; D000328:Adult; D019943:Amino Acid Substitution; D002648:Child; D002675:Child, Preschool; D002863:Chromogenic Compounds / Q000032:analysis; D003124:Colorimetry / Q000379:methods; D005169:Factor VIII / Q000032:analysis / Q000235:genetics* / Q000276:immunology / Q000627:therapeutic use; D005260:Female; D056726:Genetic Association Studies; D006467:Hemophilia A / Q000097:blood / Q000150:complications / Q000175:diagnosis / Q000235:genetics*; D006470:Hemorrhage / Q000209:etiology / Q000628:therapy; D006801:Humans; D007118:Immunoassay; D007518:Isoantibodies / Q000096:biosynthesis; D008297:Male; D020125:Mutation, Missense; D010314:Partial Thromboplastin Time; D017354:Point Mutation; D017434:Protein Structure, Tertiary; D011933:Reagent Kits, Diagnostic; D012680:Sensitivity and Specificity; D013916:Thrombelastography / Q000379:methods
chemical_list: D002863:Chromogenic Compounds; D007518:Isoantibodies; D011933:Reagent Kits, Diagnostic; C078147:F8 protein, human; D005169:Factor VIII