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Levels of Equivalence for Various Measurements of Coumarin Activity

R. J. Tat, M.D.; A. E. Lewis, M.D.
JAMA. 1962;180(9):744-746. doi:10.1001/jama.1962.03050220036007c.
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THE PURPOSE of the studies reported here is to determine the statistical relationship between the measurements of anticoagulation by the one-stage method of Quick, Owren's thrombotest, and the prothrombin-proconvertin method (hereinafter referred to as P and P). Included is an evaluation of the Lee-White clotting time as an over-all test of the clotting mechanisms.

The adequacy of prothrombin measurements for the regulation of the dose of coumarin has been questioned. It has been pointed out that coumarin derivatives depress several clotting factors. Presumably, each factor involved is depressed proportionately in most cases. However, in occasional instances a disproportionate depression of one or more factors may occur. The nature of the assay methods for prothrombin precludes the recognition of this possibility until hemorrhage has occurred.

Owren, in an attempt to solve this problem, has presented a reagent, thrombotest, in which, he claims, the relative concentrations of clotting factors are balanced at


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