Preparation of canine factor VII deficient substrate plasma.

Abstract

Abstract An essential reagent for the specific one-stage assay of clotting factor VII (proconvertin) is substrate plasma containing an adequate complement of fibrinogen, factor II (prothrombin), factor V (proaccelerin), and factor X (Stuart) but deficient in factor VII. In the past, such plasma was available only from patients homozygously deficient in factor VII, and frequently was in scarce supply. A method is described in which mongrel dogs are given a large single intravenous injection of warfarin. Because canine plasma has a high level of factor X, a point in time following warfarin administration may be selected at which the plasma factor VII level has fallen to undetectable levels while the plasma factor X level is still over 40 per cent of normal (human). A variety of plasmas were simultaneously assayed for factor VII with canine and human factor VII deficient substrate plasmas. The results of these comparisons indicate that the use of canine factor VII deficient substrate plasma provides a reliable method for assaying factor VII.