Differential Consumption of Coagulation Factors Resulting from Activation of the Extrinsic (Tissue Thromboplastin) or the Intrinsic (Foreign Surface Contact) Pathways

1. The consumption of coagulation Factors IX, X, and XI was studied innormal whole blood clotted with celite (intrinsic activation) or tissue thromboplastin (extrinsic activation).

2. During these studies an assay method for Factor XI was developed whichwas not influenced by the presence of tissue thromboplastin. The assay methodis based on the thromboplastin generation principle.

3. When blood clotted in silicone treated tubes, the serum and plasma concentrations of Factors IX, X, and XI were almost identical, indicating that littleconsumption or activation of these factors had occurred.

4. In the presence of celite, coagulation Factors IX and XI are consumed,whereas Factor X is consumed only slightly.

5. In the presence of tissue thromboplastin, Factor X is consumed, whereasFactors IX and XI are not consumed.

6. In the presence of both celite and thromboplastin, the thromboplastindecreased the consumption of Factors IX and XI produced by celite.

7. The study of serum coagulation factor levels may provide evidence as towhether the coagulation process had been initiated by the intrinsic (foreignsurface contact) or extrinsic (thromboplastin) pathways.

Submitted on May 9, 1966 Accepted on July 21, 1966