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The page below is a sample from the LabCE course Antiplatelet and Anticoagulant Pharmacology for the Laboratory Professional. Access the complete course and earn ASCLS P.A.C.E.-approved continuing education credits by subscribing online.

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Clinical Correlation: Hemophilia A and B

Hemophilia is a condition that results in increased bleeding due to a coagulation factor deficiency. Unlike the bleeding from platelet disorders, which is more superficial, bleeding from coagulation factor deficiencies is much deeper. Patients with coagulation factor deficiencies like hemophilia experience deep joint bleeding (hemarthrosis) and hematomas, for example. Due to the genetic inheritance pattern of hemophilia, this is mainly seen in genetic males. Genetic females are usually only carriers of hemophilia and do not display the symptoms of the disease.
  • Hemophilia A = deficiency of factor VIII
  • Hemophilia B = deficiency of factor IX
Laboratory diagnosis of hemophilia:
  • Prolonged aPTT, since factors VIII and IX are both in the intrinsic pathway and the intrinsic pathway is tested by the aPTT assay.
  • The PT is normal, as it tests for the extrinsic pathway coagulation factors.
  • Factor VIII and factor IX assays ultimately determine the level of activity of each factor, respectively.
Bleeding in hemophilia depends on how much activity of factor VIII or IX is present. 25% or more factor activity results in no persistent symptoms, but the patient may have excessive bleeding with major medical procedures or after trauma. When less than 10% of factor activity is present, the patient will see spontaneous deep bleeding events.
Treatment of hemophilia:
  • Desmopressin if mild hemophilia A. Desmopressin causes release of factor VIII stores.
  • Factor VIII or IX replacement for more severe hemophilia.