Summary
The plasma levels of coagulation factor VII and fibrinogen are well known risk factors
for arterial thrombosis. We tested the hypothesis that this association also exists
for venous thrombosis. Additionally, MspI and Haelll polymorphisms in the factor VII
and fibrinogen genes have recently been reported to be associated with the concentration
of both proteins in the plasma. However, no conclusion could be drawn with respect
to an increase or decrease in thrombosis risk. We undertook a population-based case-control
study, in which 199 patients with a first, objectively confirmed episode of deep vein
thrombosis, aged less than 70, and without a known malignant disorder were compared
to 199 age-and sex-matched healthy controls, to evaluate the clinical importance of
these reported findings.
For fibrinogen we found a positive level-related association between the plasma fibrinogen
level and thrombotic risk. Subjects with a plasma fibrinogen greater than 5 g/1 had
an almost 4-fold increase of thrombosis risk. The frequencies of the different Haelll
genotypes were out of balance only for the thrombosis patients, with a deficit of
the H1H2 genotype. Possession of an H1H2 genotype was associated with a 40% reduction
in thrombosis risk.
For factor VII, neither the plasma level nor the MspI genotypes were related to deep
vein thrombosis, although possession of a M2 allele was clearly associated with significantly
lower factor VII levels. The frequencies of the Mspl-genotypes were the same for patients
and control subjects and, exhibited Hardy-Weinberg equilibrium.
Our results support that plasma fibrinogen, a determinant of arterial thrombosis is
also a risk factor for venous thrombosis, while factor VII plasma concentration is
unrelated to deep vein thrombosis, which is supported by the data from the DNA analysis
of polymorphisms.
