Urine Test for Heart Disease Shows Promise
WEDNESDAY, April 29 -- A urine test to detect coronary artery disease has worked well in a small trial, German researchers report.
The test looks for fragments of the protein collagen, which plays a major role in blocking heart arteries, said study author Dr. Constantin von zur Muehlen, a fellow in cardiology at University Hospital Freiberg. He was scheduled to report the findings Wednesday at an American Heart Association meeting in Washington, D.C.
"Collagen forms a fibrous cap on the epithelium, the lining of the arteries," Muehlen explained. "These fibrous caps produce collagen fragments."
High concentrations of those fragments, called proteomes, in urine can signal atherosclerosis (hardening of the arteries), which can lead to a heart attack, Muehlen said.
The urine test was done for 67 people with symptoms of coronary artery disease, he said. Two techniques to detect proteins, mass spectrometry and capillary electrophoresis, were used to find levels of 17 protein fragments that the researchers had identified as being associated with atherosclerosis.
When the results were compared to coronary angiography, an X-ray exam that is a standard method for diagnosing atherosclerosis, the urine tests were found to be 84 percent accurate, Muehlen said.
But a urine test to detect heart disease will not be developed quickly, he said. The German researchers have gone back to the laboratory, working with a strain of mice genetically engineered to develop coronary artery disease as they age.
"We went to this mouse model and found that, over time, the pattern of proteomes becomes more heavily expressed," Muehlen said. "The older the animal, the more extreme the pattern will be."
While he hopes to do a larger human study, no timetable for one has been set, Muehlen said.
More animal studies are needed to fill in knowledge gaps, he said. "We don't know if stable regions of atherosclerosis produce more collagen than unstable regions," Muehlen explained. Unstable collagen is more likely to rupture, blocking an artery completely.
This is not the first report of a urine test for coronary artery disease. In 2007, physicians at Brigham and Women's Hospital in Boston found that the presence of the protein albumin in urine of people with stable cardiovascular disease indicated an increased risk of death.
Albumin is normally found in blood, but not in urine. Leakage of albumin into the urine indicates damage to the blood vessels of the kidney, and so points to an increased risk of cardiovascular death, the researchers said.
The German study is "interesting, but I'd be cautious," said Dr. Alan Daugherty, director of the Cardiovascular Research Center at the University of Kentucky.
"In general, it obviously would be desirable to be able to diagnose coronary artery disease without an angiogram," Daugherty said. "There has been a tremendous amount of effort looking for biomarkers."
But a good deal of work is needed to move the results of the study toward clinical use, he said. "We've been trying to do something like this for decades," Daugherty noted.
Learn about coronary artery disease from the U.S. National Heart, Lung, and Blood Institute.
Posted: April 2009
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