An association between the factor VII coagulant activity and thrombin activity induced by surface/cold exposure of normal human plasma

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Abstract
Summary. To test whether factor VII activation correlated with the generation of thrombin activity when plasma was exposed to a glass surface and reduced temperature, an association was sought between the changes in factor VII clotting activity (VIIc) and fibrinopeptide A concentration (an index of thrombin activity) in platelet‐poor citrated plasma from 42 healthy adults. The Spearman rank correlation (rs) between responses was 0.82 (P < 0.001). The VIIc assay response to surface/cold exposure was unaffected when thrombin was suppressed by hirudin. An assay for factor VII activity based upon its activation of tritiated factor X revealed an association between the increase in fibrinopeptide A concentration and reduction in functional factor VII concentration during activation of a subset of 22 plasma samples (rs= ‐0.62; (P < 0.003). This loss of functional factor VII was probably due to conversion of active factor VII to its non‐functional end‐product by factor Xa. The results suggest that VIIc is an index of flux within the coagulation system and support the hypothesis that a high VIIc is an indicator of a hypercoagulable state.