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16-04-2012 | Cardiology | Article

Pneumonia may increase VTE risk


Free abstract

MedWire News: People who have had pneumonia are at significantly increased risk for subsequently developing venous thromboembolism (VTE), show results of a large, population-based, case-control study.

The increased risk is highest among carriers of the factor V Leiden or prothrombin G20210A prothrombotic mutations, in whom it is up to 20-fold greater than in noncarriers who have not had pneumonia, report researchers in the Journal of Thrombosis and Haemostasis.

Suzanne Cannegieter (Leiden University Medical Center, the Netherlands) and colleagues explain that although previous retrospective studies have indicated that pneumonia is associated with an increased risk for VTE, there is uncertainty over the extent to which this risk is causal. Particularly as pneumonia is often accompanied by transient periods of immobilization and may be associated with smoking and reduced physical activity, all of which are also risk factors for thrombosis.

The researchers therefore aimed to determine if pneumonia is independently associated with an increased risk for VTE in a group of 4956 patients with deep-vein thrombosis (DVT) or pulmonary embolism (PE), and in 6297 age- and gender-matched controls without VTE.

They found that a period of pneumonia in the year before the thrombotic event was reported in 7.2% (n=307) of patients and in 1.5% (n=87) of controls.

Furthermore, participants with prior pneumonia were five times more likely to have VTE than participants without pneumonia. This risk was not attenuated after adjustment for age, gender, classic thrombosis risk factors (eg, trauma, surgery, and malignancy), and an unhealthy lifestyle (ie, obesity, smoking, and low physical activity). However, further adjustment for immobilization reduced the odds ratio (OR) for VTE associated with prior pneumonia to 3.8.

This indicates that immobilization could play a role in the mechanism of pneumonia leading to venous thrombosis, say the researchers.

When the team analyzed the combined effect of prothrombotic genes and pneumonia on VTE risk, they found that factor V Leiden carriers without pneumonia had a 3.4-fold increased risk for VTE compared with noncarriers without pneumonia. Participants with pneumonia who were noncarriers of factor V Leiden had a 5.5-increased risk, while those who had factor V Leiden and pneumonia had a 17.8-fold increased risk compared with noncarriers without pneumonia.

A similar joint effect was observed for prothrombin G20210A and pneumonia on venous thrombosis risk, with corresponding adjusted odds ratios of 2.8, 5.3, and 20.7.

Cannegieter and co-authors conclude that their findings "could point towards a causal association between pneumonia and VTE."

The joint effects for both factor V Leiden and prothrombin G20210A in combination with pneumonia warrants further investigation into the need for a different thromboprophylactic approach in these patients, they add.

By Laura Cowen

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