Is the aPTT always prolonged in someone with hemophilia?
• The aPTT may not be prolonged in mild factor IX or VIII deficiency. • The sensitivity of each laboratory in detecting moderate deficiencies may vary; therefore, the aPTT should not be used as a screening test in patients with a suspicious clinical history. • The aPTT is relatively insensitive in patients with Von Willebrand disease; it is often normal in this disorder and should not be used as a screening test. • Rare bleeding disorders exist in which the PT and aPTT are expected to be normal; consultation with the IHTC is available to discuss diagnostic issues and problems in persons who are bleeding despite normal coagulation values.
