HEMOPHILIA B DIAGNOSIS

CLINICAL PRACTICE GUIDELINES
Hemophilia and07-07

Hemophilia B Diagnosis
" Hemophilia" refers to X-linked bleeding disorders in which there is a deficiency (activity level of 35% or less) of either Factor VIII (hemophilia A, classic hemophilia) or Factor IX (hemophilia B, Christmas disease). The incidence of hemophilia is about 1 in 5000 males; of those affected, roughly 80% to 85% have hemophilia A and the remainder hemophilia B.<8>
Coagulation tests for hemophilia show a prolonged activated partial thromboplastin time (APTT), a normal one-stage prothrombin time (PT) and a normal bleeding time. In hemophilia A, Factor VIII activity is decreased or absent, whereas the level of von Willebrand factor (antigen and ristocetin cofactor activity) is normal. In hemophilia B, Factor IX activity is decreased or absent. In patients with mild hemophilia, the APTT may be normal depending on the reagent used, and the appropriate factor assays must be used to confirm/exclude the diagnosis.
In both hemophilia A and B, there is usually a strong correlation between the level of clotting factor activity and the clinical severity of the disease (Table 1).<9>
Diagnosis of hemophilia in the male infants of known or suspected carriers should be confirmed soon after birth, particularly if a surgical procedure such as circumcision is contemplated.

Table 1. Correlation of clotting factor activity and severity of hemophilia <9>
Clotting factor activity level * (%) Clinical Severity of hemophilia
< 1 Severe: spontaneous musculoskeletal and internal bleeding
1-5 Moderate: occasional spontaneous musculoskeletal bleeding
5-35 Mild: delayed-onset bleeding after trauma, surgery, and dental extraction

*1 U/mL (100% activity) is the clotting-factor activity present in 1 mL of average normal plasma
von Willebrand’s Disease: 1.diagnosis, comprehensive care and assessment (Edition 2, Update 2 [1999-])

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Last Updated (Monday, 16 August 2010 17:55)