Fast Five Quiz: Bleeding Disorders

Emmanuel C. Besa, MD

Disclosures

July 11, 2019

Laboratory studies for suspected hemophilia B include a complete blood cell count, coagulation studies, and a factor IX assay. Never delay indicated coagulation correction pending diagnostic test results.

For factor IX assays, levels are compared with a normal pooled-plasma standard, which is designated as having 100% activity or the equivalent of factor IX U/mL. Normal values are 50%-150%. Values in patients with hemophilia are as follows:

  • Mild: > 5%

  • Moderate: 1%-5%

  • Severe: < 1%

Spontaneous bleeding complications are severe in individuals with undetectable activity (< 0.01 U/mL), moderate in individuals with activity (2%-5% normal), and mild in individuals with factor levels > 5%.

Usually, the aPTT in patients with hemophilia is prolonged; however, a normal aPTT test result does not exclude mild or even moderate hemophilia because of the relative insensitivity of the test. The aPTT is significantly prolonged in severe hemophilia.

Ultrasonography is useful in the evaluation of joints affected by acute or chronic effusions in patients with hemophilia B. This technique is not helpful for evaluating the bone or cartilage. Special studies such as angiography and nucleotide bleeding scan may be clinically indicated.

Read more about the workup of hemophilia B.

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