Have normal blood coagulation. This is defined by either a prothrombin time and aPTT within the laboratory's normal range (11.8-14.7 sec and 23.4-34.5 sec respectively), or by hemostatic coagulation factor levels in patients with prolonged prothrombin times and/or aPTTs that are explained by mild factor VII deficiencies (30-40 %) or by lupus anticoagulants. If a patient has a prolonged aPTT due to a lupus anticoagulant, he/she must have a normal thrombin time in order to be included in the study.