Factor X phenomenon

¹ Department of Hematology, Division of Laboratories, Montefiore Hospital, New York City

Storage of human serum at refrigerator temperature yields a reagent which poorly supports thromboplastin generation. Although the degree of this defect showed no correlation with the serum prothrombin content, a high serum prothrombin was found to preserve activity. The clotting defect in stored serum was shown to be different from that in Stuart factor-deficient serum, as determined by mixing studies in both prothrombin and thromboplastin generation procedures. It is concluded that the factor X phenomenon is unique, although these studies do not establish factor X as a chemical entity.