Enzyme studies on human blood. VII.: Prothrombin as Determined with the Isolation Technic, in Patients Receiving Dicumarol

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Abstract
Plasma prothrombin levels of 10 thrombo-embolic patients receiving dicumarol were determined by both the one-stage and the new isolation technics. During the first week of therapy there was a discrepancy between the levels obtained by the 2 technics. The one stage prothrombin dropped to a 30% level on the 3d day, whereas the isolation prothrombin values did not reach this level for 6 days or longer. Beyond one week of therapy there was excellent correlation in the results obtained by the 2 technics. In the detn. of, prothrombin by the isolation technic, Fraction I is first precipitated by the low temp.-alcohol method of Cohn and co-workers from 4 ml. of citrated plasma. From the supernatant fluid the prothrombin fraction is precipitated at pH 5.05 and O[degree]C. This prothrombin fraction is then activated with an optimum concn. of Ca and thromboplastin, and the resulting thrombin is titrated. Standardized reagents of human origin are used throughout the procedure.