Abstract: The present invention is directed to methods to rapidly assess the overall coagulant properties of a patient's blood sample by inhibiting the activation of the intrinsic contact activation pathway of coagulation and activating the extrinsic pathway of coagulation. When the sample is whole blood, the resulting clotting time represents the overall coagulant activity of the plasma and cellular components of the blood, which is indicative of existing or impending pathology arising from abnormal coagulability. The invention also provides a method for measuring the risk of a patient for a thrombotic event and for monitoring the effectiveness of procoagulant/anticoagulant therapy. A blood collection apparatus suitable for use in for performing the methods of the invention is also provided.