Coagulation factors evaluated in a group of patients with borderline hypertension. The following tests were carried out: prothrombin time (PT) and partial thromboplastin time (PTT), Factor VIII coagulant activity, Factor VIII antigen and Factor VIII ristocetin cofactor, Factor XII and Factor XI activities. These tests were selected for their relationship to the contact coagulative activation near the vascular wall. Comparing the results with those of normal controls, Factor VIII coagulant activity, Factor XII and PTT levels were significantly higher. Other tests were all within normal limits in both groups. High Factor VIII and Factor XII levels associated with PTT shortening suggest that an increased synthesis and/or release of these coagulation factors was present in our patients. Activated coagulation seems to be present in borderline hypertension before the appearance of clinical signs of vascular lesions
