Laboratory studies for suspected hemophilia include a complete blood cell count, coagulation studies, and factor assays. If the factor activity is less than 40% of normal, hemophilia is usually the diagnosis. Molecular genotyping is recommended to confirm the diagnosis and aid in prediction of disease severity. Never delay indicated coagulation correction pending diagnostic testing.
Usually, the aPTT is prolonged in patients with hemophilia; however, a normal aPTT does not exclude mild or even moderate hemophilia. The aPTT is significantly prolonged in severe hemophilia. Platelet counts are usually normal. On coagulation studies, the bleeding time and prothrombin time (which assesses the extrinsic coagulation pathway) are typically normal in patients with hemophilia A or hemophilia B.
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Cite this: Emmanuel C. Besa. Fast Five Quiz: Hemophilia - Medscape - Sep 21, 2021.