Infection is an Independent Risk Factor for Venous Thromboembolism

SUMMARY: The Center for Disease Control and Prevention (CDC) estimates that approximately 1-2 per 1000 individuals develop Deep Vein Thrombosis/Pulmonary Embolism (PE) each year in the United States, resulting in 60,000-100,000 deaths. Venous ThromboEmbolism (VTE) is the third leading cause of cardiovascular mortality, after myocardial infarction and stroke. Currently, VTE prophylaxis is recommended only for hospitalized patients and this intervention prevents only about 50% of the VTE burden in the general community. Therefore, identifying non-hospitalized individuals at risk for VTE is important to further reduce the incidence of VTE and improve survival.

Infections, which are common, have been associated with VTE. These episodes however have been labeled idiopathic, as these patients are not pregnant or postpartum, have not been on hormone therapy or hormonal contraception, do not have active malignancy and have not had recent nursing home confinement, trauma, fracture, immobilization or leg paresis. Infection promotes thrombosis from endothelial damage and tissue factor-induced activation of the procoagulant pathway, as well as downregulation of the endogenous anticoagulant pathway, and inhibition of fibrinolysis. Venous thrombosis has also been linked to neutrophil activation and promotion of platelet aggregation through the P-selectin mediated pathway.

In order to address the independent association of recent infection with VTE, the authors performed a population-based, case-control study within their local community, nested within the population of Olmsted County, Minnesota, to estimate the magnitude of risk of VTE due to active infection, taking advantage of Rochester Epidemiology Project (REP) resources, to identify all Olmsted County residents with incident VTE and matched controls drawn from the same population. The authors identified 1303 cases of objectively diagnosed incident Deep Vein Thrombosis or Pulmonary Embolism over the 13-year period from 1988 to 2000 along with 1494 matched controls without VTE. They then looked for an association of infection and site of infection with VTE, after adjusting for all other known VTE risk factors.

It was noted that infection and site of infection were risk factors for VTE, compared with no infection. Any infection increased the odds of VTE by 4.5 fold (P<0.0001) compared with no infection, when unadjusted for other VTE risk factors. The odds of VTE due to any infection was 2.4 fold higher compared with no infection, after adjusting for all established VTE risk factors (P<0.0001). An Odds Ratio (OR) is a measure of association between an exposure and an outcome. The OR represents the odds that an outcome will occur given a particular exposure, compared to the odds of the outcome occurring in the absence of that exposure. Intra-abdominal infection imparted the highest magnitude of risk (OR, 18), followed by oral infection (OR, 12), systemic bloodstream infection (OR, 11), lower respiratory infection such as pneumonia (OR, 3.6), and symptomatic urinary tract infection (OR, 2.2). Oral infection was a significant independent risk factor for VTE compared with no infection, after adjusting for other risk factors and for other infections (OR, 11.6). Oral candidiasis comprised 75% of oral infections among VTE patients. It is conceivable that oral candidiasis is a potential marker for patient debility that may be a VTE risk factor, not captured by the other covariates.

It was concluded that infection is an independent risk factor for VTE and VTE risk can be further stratified by site of infection. Is Infection an Independent Risk Factor for Venous Thromboembolism? A Population-Based, Case-Control Study. Cohoon KP, Ashrani AA, Crusan DJ, et al. The American Journal of Medicine 2018;131:307-316