Abstract
When blood clots in the test tube, only a portio of the prothrombin is consumed. The amount of prothrombin activity remaining in the serum has recently been shown to have considerable clinical significance(1). Deficiencies in the the anti-hemophilic globulin (thromboplatinogen) or the platelet-tissue thromboplastic enzyme result in less consumption of prothrombin and consequently more residual serum prothrombin activity. Quick (1) has demonstrated that serum prothrombin activity can be estimated by using deprothrombinized plasma as a source of fibrinogen. His data indicate that incubation of the whole clot may alter serum prothrombin activity quite differently from similar incubation of the separated serum. This fact is probably responsible for much of the difficulties and multipliticy of technics suggested for the estimation of prothrombin consumption(3). Quick suggests that prothrombin consumption be determined by incubating 3 aliquots of blood for various time intervals before separation of the serum and doing 7 estimations of prothrombin activity of these 3 sera after various periods of further incubation. This paper presents data describing serially the pattern of serum prothrombin activity following varying periods of incubation before and after separation of the serum from the clot. These data are sought in order to determine the conditions which will best reflect the prothrombin-consuming property of a specimen of blood. Knowledge of these conditions may make it possible to estimate prothrombin consumption reliably and reproducibly by a single determination on one aliquot of blood. Data are also presented on the use of fibrinogen in place of “prothrombin-free” rebbit plasma for determining serum prothrombin activity. A standardized, dry preparation containing fibrinogen, thromboplastin, CaCI2, and NaCI in optimal amounts is employed.∗ The preparation is free from prothrombin, oxalate, and citrate(2) and is stable at 5° for at least several months.
The authors wish to thank Dr. R. Kroc and E. White of Chilcott Labrotaries, Morris Plains, N. J., for preparing this reagent.
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