A study of the plasma thrombin time.

Abstract Prolongation of the plasma thrombin time was found in a wide variety of diseases and in late pregnancy and the newborn. Further study revealed the increase in plasma thrombin time to be a complex phenomenon due to a multiplicity of factors, usually occurring in combination. The most constant abnormality appeared to be a deficiency of a plasma substance aiding the conversion of fibrinogen to fibrin. An increase in plasma fibrinogen appeared to be a contributing factor. Circulating anticoagulant was encountered only once and increased antithrombin activity appeared to play a relatively insignificant role in the delayed plasma thrombin time. The deficient substance in plasma, aiding fibrin clot formation, did not appear to be platelets or any of the known plasma or serum coagulation factors. The data presented suggest that the deficient substance is albumin or a substance related to albumin. Clinically, prolongation of the plasma thrombin time did not appear to result in significant hemorrhagic manifestations.