How does the LA affect prothrombin time and aPTT?
PT should not be affected by lupus anticoagulants (LA), especially with the newer assays that are insensitive to this antiphospholipid antibody. Over half of patients with LA have a prolonged aPTT. However, a normal aPTT does not exclude the presence of LA.
Pearl : if an APS patient has a prolonged PT, they may also have antibodies against factor II (prothrombin), which can lead to hypoprothrombinemia causing an increased chance of hemorrhage when they are anticoagulated
