Infection may double the odds of venous thromboembolism

Having an infection of any type more than doubles the odds (2.4-fold) of venous thromboembolism (VTE) compared to having no infection, reported Mayo Clinic researchers in a recent study in The American Journal of Medicine.

Site-specific infections—including intra-abdominal, urinary tract, blood stream, and lower respiratory infections—also raise the risk for VTE. Surprisingly, this also includes oral infections, the researchers found.

“Infection and infection sites are independent risk factors for venous thromboembolism and should be considered as potential indications for venous thromboembolism prophylaxis,” wrote cardiologist and vascular medicine specialist Kevin P. Cohoon, DO, MSc, and fellow researchers from the Mayo Clinic, Rochester, MN.

Prophylaxis of VTE is currently recommended only for hospitalized patients. But, even if all hospitalized patients received universally-effective prophylaxis, only about half of the VTE burden in the community would be prevented, the Mayo Clinic researchers pointed out.

“To further reduce the venous thromboembolism burden, better methods are needed to identify the non-hospitalized individual at risk for venous thromboembolism,” they wrote.

Previous studies using administrative data have associated infection with thromboembolism. However, the validity of these previous studies is uncertain, the researchers noted, because these data have a very poor predictive value for identifying objectively-diagnosed VTE when compared to direct medical record review.

For that reason, Dr. Cohoon and colleagues performed a case-control study within the population of Olmsted County, MN. They identified 1,303 residents who were diagnosed with incident VTE between 1988 to 2000, as well as 1,494 age-matched controls from the same population. Among these patients, 39.4% of VTE cases and 12.7% of controls had an infection in the previous 92 days.

After a multivariable analysis adjusted for other VTE risk factors, the researchers found that the odds of VTE due to any infection was 2.4-fold higher than no infection. Antibiotics were associated with 5.2-fold increased odds of VTE, and fever was associated with 14.5-fold greater odds.

For specific infection sites, the odds of VTE were 2.24-fold higher in those with symptomatic urinary tract infection, 3.64-fold higher in those with pneumonia, 10.69-fold higher in those with systemic/blood stream infection, 11.61-fold higher in those with oral infection, and 17.8-fold higher in those with intra-abdominal infection compared to those with no infection. For all remaining infections combined, the odds of VTE were 1.56-fold higher.

“We were surprised to find an independent association of oral infection with venous thromboembolism; to our knowledge, this finding is novel,” Dr. Cohoon and colleagues noted. “Oral candidiasis comprised 75% of oral infections among venous thromboembolism cases. Oral candidiasis is a potential marker for patient debility, which may be a venous thromboembolism risk factor not captured by the other covariates we tested.”

Given these findings, future studies are needed to determine what effect VTE prophylaxis will have among outpatients with high VTE-risk infections, the authors concluded.