Simple Kidney Test Predicts Heart Death

New study strengthens connection between two organ ailments

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HealthDay Reporter

MONDAY, Oct. 11, 2004 (HealthDayNews) -- A new blood test could provide the quick, easy marker of kidney function that cardiologists need to assess patients being treated for heart attacks or other serious coronary events, Swedish researchers report.

The test measures blood levels of cystatin C, a molecule that is produced by most cells and is filtered out of the blood by the kidneys. Testing for cystatin C gave a highly accurate prediction of survival for patients who suffered heart attacks, said a report in the Oct. 12 issue of Circulation by physicians at the Uppsala Research Center.

The study of 726 patients with a type of heart attack called non-ST-elevation acute coronary syndrome found that 55 percent of those with the highest blood levels of cystatin C died, compared to 7 percent of those with the lowest levels, the report said.

"The present study strongly suggests that measuring plasma cystatin C is not only more practical at bedside by making complicated calculations unnecessary, but also will substantially improve the early assessment of these patients," the researchers wrote.

Cardiologists routinely check kidney function for such patients because "kidney disease influences heart disease outcome," said Dr. L. Lee Hamm, a professor of medicine at Tulane University and chairman of the American Heart Association Council on the Kidney and Cardiovascular Disease.

The most commonly used test measures blood levels of a protein called creatinine, but analysis of that test requires complex calculations based on a patient's age, gender and weight.

The cystatin C test "is a lot more practical because it doesn't require those additional calculations," said study author Dr. Tomas Jernberg, an associate professor of medicine at Uppsala. "An increased level is associated with an increased risk regardless of age, gender or weight."

The Swedish report looks interesting, Hamm said, but "this one paper would have to be confirmed by other studies." The cystatin C test used in the study is not widely available in the United States "and right now some people think that other kidney function tests might turn out to be as good or better," he said.

What is clear is that "in the last two or three years, people have been thinking about how kidney function influences heart disease outcome," Hamm said.

Two studies reported just last month reflect that interest. One found a direct relationship between reduced kidney function and the incidence of cardiovascular problems such as heart attacks in more than 1.1 million people enrolled in the Kaiser Permanente of North California health plan.

The second study, which included more than 14,000 persons who survived heart attacks, found that the risk of cardiovascular events and of death from all causes went up by 10 percent with every 10-point drop in glomerular filtration rate, the measure of the kidney's ability to remove impurities from the blood.

The exact reason for the link between kidney function and heart problems is not completely understood, Hamm said.

"Part of it is probably that many people with kidney disease have other problems, such as high blood pressure or accelerated atherosclerosis [clogging of the arteries]," he said. "Kidney disease serves as a marker of those problems."

More information

The kidney-heart relationship is explained by the American Heart Association.

SOURCES: Tomas Jernberg, M.D., Ph.D., professor, medicine, University of Uppsala, Sweden; L. Lee Hamm, M.D., professor, medicine, Tulane University, New Orleans: Oct. 12, 2004, Circulation

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