What is the significance of a prolonged PT in a patient with lupus anticoagulants?
A prolonged PT might indicate an extremely high level of LA but could also indicate the presence of a prothrombin (factor II) deficiency. This condition can be caused by hereditary factor II deficiency, liver disease, vitamin K deficiency, or anticoagulation with warfarin. In addition, acquired factor II deficiency due to autoantibodies to factor II is rarely associated with autoimmune disorders, including SLE. It is extremely important to detect factor II deficiency because it is associated with excessive bleeding rather than hypercoagulability. If both aPTT and PT are prolonged, a prothrombin level should be measured directly to exclude a deficiency.