The Measurement of the Ratio of Factor VII Activity Utilizing Bovine Tissue Thromboplastin and Human Tissue Thromboplastin in Hypercoagulable State

Abstract

It has been known that bovine tissue thromboplastin reacts more with activated human factor VII than with non-activated factor VII, whereas human tissue thromboplastin interacts equally with both activated and non-activated human factor VII. Thus the ratio of factor VII activity measured with bovine tissue thromboplastin to that measured with human tissue thromboplastin (b/h) reflects the relative amount of activated factor VII. In this report, we provide evidence that the b/h ratio is a very sensitive and specific indicator of the stages of accelerated coagulation. Upon activation of the extrinsic coagulation pathway by addition of a smal amount of tissue thromboplastin to blood in a plastic tube, the b/h ratio was increased from 1.0 to 1.6. The ratio was increased up to 1, 000-fold by cold induced activation of factor VII in plasma from pregnant women. In vitro activation of the intrinsic pathway by incubation of plasma in a glass tube at 37°C or by addition of kaolin raised the b/h ratio up to 98-fold and 8-fold, respectively. Patients in hypercoagulable state were divided into three groups; group A (non-DIC), group B (pre-DIC), and group C (DIC). The b/h ratios in group A (1.393±0.782) and in group C (1.260±0.455) were not significantly different from that of normal controls (1.086±0.154). However, in group B, the b/h ratio (2.868±1.993) was significantly higher than that in normal controls (p<0.05). Several lines of evidence indicated that the increased b/h ratio in group B plasmas was the result of accelerated activation of factor VII due to hypercoagulability. Thus, the b/h ratio would be a useful clinical marker to detect hypercoagulable state such as pre-DIC.