Urine Test Predicts Vein Clot Risk
TUESDAY, May 5 -- A higher-than-normal level of the protein albumin in urine indicates an increased risk of dangerous blood clots in the deep veins of the lungs and legs, a Dutch study finds.
These venous thromboembolisms (VTEs) include deep vein thrombosis (DVT), a clotting in the lower extremities which gained recent notoriety when it occurred in passengers on long-haul flights. These clots can become dangerous if they travel to the lungs to produce a pulmonary embolism.
But the presence of albumin in urine might warn of VTE risk, the new study found.
"Microalbuminuria is a known risk factor for arterial conditions such as myocardial infarction [heart attack] and stroke," noted Bakhtawar K. Mahmoodi, a medical student at the University of Groningen who is lead author of a report in the May 6 issue of the Journal of the American Medical Association. "Now it is also found to be a risk factor for venous thromboembolism. This is the first time it has shown to be a risk factor for VTE."
Tests to detect albumin and other proteins in the urine now are commonly done to help assess the risk of problems caused by damage to the arteries, which carry blood from the heart. Those tests now generally are done in people in people known to be at risk because of conditions including diabetes and high blood pressure. Those conditions can reduce the function of kidneys, which remove proteins from the blood.
This latest study indicates that such a urine test could also help assess the risk of problems in the veins, which carry blood back to the heart, said Dr. Ron T. Gansevoort, an associate professor of nephrology at Groningen, who oversaw the research.
The report was based on an ongoing study designed to include all adult residents of Groningen. It included data on almost 8,600 adults, 129 of whom had venous clots during the study period of more than eight years -- an average incidence of 0.14 percent per year.
The incidence of such clots was 40 percent higher for people with slightly elevated urine levels of albumin and more than twice as high for people with more elevated levels than for those with normal levels, after adjustment for known risk factors such as diabetes, the researchers found.
The report is one of several that have demonstrated a possible value of urine tests to help determine the risk of cardiovascular disease. A German research group reported recently that a urine test looking for fragments of a different protein, collagen, might help detect an increased risk of heart disease.
And in 2007, physicians at Brigham and Women's Hospital in Boston found that high levels of albumin in urine of people with stable cardiovascular disease indicated an increased risk of death.
Studies have shown that high urine levels of albumin have a greater association with arterial condition than with venous problems, Gansevoort said. "There are two sides to the coin," he said. "One is how often you find the problems. The incidence of arterial problems is twice as high than for venous problems."
"Then, how serious is an arterial problem against a venous problem? If you have a myocardial infarction or a stroke, it is more serious than a venous thrombosis on a leg. But pulmonary [lung] emboli are very important problems," he said.
The new study does not indicate a need for using urine tests as a mass screening method, Gansevoort said. "But if someone comes into my clinic who I suspect might have venous thrombosis or embolism, possibly with a family history, I might add a test for microalbuminuria. If there is shortness of breath showing that there might be a pulmonary embolism, I can use a test for microalbuminuria in diagnosis."
The why and how of a urine test for albumin is explained by the Cleveland Clinic.
Posted: May 2009
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