Summary
Introduction. Previous investigations have suggested a lower prevalence of the factor V Leiden
mutation in patients with pulmonary embolism, as compared to patients with deep leg
vein thrombosis. Methods. We studied unselected patients with pulmonary embolism, in whom we also assessed
the presence of deep vein thrombosis by ultra-sonography. We assessed the prevalence
of heterozygosity for the factor V Leiden mutation and compared the outcome of patients
with a normal ultrasound (primary pulmonary embolism) to those with an abnormal ultrasound
(combined form of venous thromboembolism). Furthermore, we performed a literature
search to identify all articles regarding the prevalence of heterozygous factor V
Leiden mutation in patients with primary deep vein thrombosis, primary pulmonary embolism
and a combined form of venous thromboembolism. We calculated a (common) odds ratio
for these 3 manifestations of venous thromboembolism, including the current findings.
Results. In 92 patients with proven pulmonary embolism, 25 (27%) had also an abnormal ultrasound.
In these patients, the prevalence of the factor V Leiden mutation was 24% (95% CI
9%-45%), whereas the mutation was present in 5 of 67 patients with primary pulmonary
embolism (7%; 95% CI 2%-16%). The literature analysis indicated the common odds ratio
for the presence of heterozygous factor V Leiden mutation in patients with primary
deep vein thrombosis, primary pulmonary embolism and the combined form of venous thromboembolism
to be 7.9 (95% CI 5-12), 3.5 (95% CI 2-6) and 6.8 (95% CI 3-14), respectively. Conclusion. In patients with primary pulmonary embolism the prevalence of the factor V Leiden
mutation appears to be half of that reported in patients with primary deep vein thrombosis.
The mechanism remains unclear.
