Interrelationship of Prothrombin and Autoprothrombin I in Thrombocytopenia Following Aminopterin Administration

¹ From the Department of Laboratories and Division of Hematology, Henry Ford Hospital, Detroit, Michigan

The poor prothrombin consumption test supported by thrombocytopenic serum has been shown in a previous publication to be due to some activity other than prothrombin—a thrombocytopenic activity. This thrombocytopenic factor or activity can be readily adsorbed on inorganic agents and eluted. The autoprothrombin I values were found to be lower in thrombocytopenic serum than in normal serum. When the patient with thrombocytopenia was treated with aminopterin, the prothrombin consumption test remained short while the autoprothrombin I values increased to that of normal serum and then fell again as the treatment was withdrawn. The prothrombin in the serum remained uniformly low throughout the treatment. The relationship of the thrombocytopenic activity and autoprothrombin I as possible derivatives of prothrombin is considered.