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Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

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The following results occur in Haemophilia A and Haemophilia B:

  • activated partial thromboplastin time (APTT); prolongation depends on the severity of the factor deficiency. Prolonged APTT plus prolonged bleeding suggests von Willebrand's disease
  • factor VIII clotting assay - low levels in Haemophilia A
  • factor IX clotting assay - low levels in Haemophilia B
  • note that in severe cases of Haemophilia B whole blood coagulation time is increased (1)

Other investigations:

  • normal tests in Haemophilia A and Haemophilia B include:
    • prothrombin time (PT)
    • bleeding time
    • normal von Willebrand factor
  • Other investigations include:
    • DNA probes - genes for Factor VIII and Factor IX have been cloned and characterised.
    • pedigree analysis - may diagnose female carriers with certainty in some situations - for example all daughters of a known haemophiliac male are obligate carriers


  1. Hoffbrand AV, Pettitt JE (1999). Essential Haematology. Blackwell Scientific Publications, Oxford.

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