Study: Test can predict further problems



The test for a certain protein would be used only in patients who already have the disease.
SCRIPPS HOWARD
A simple blood test can accurately predict the risk of heart attack, heart failure, stroke or related death in patients already known to have cardiovascular disease, a new study shows.
Research on a group of 987 men and women with stable heart disease found that the higher the levels of a certain protein in the blood, the greater the risk of a serious cardiovascular event.
The findings were published today in The Journal of the American Medical Association.
"After adjusting for all other risk factors, it's clear that this marker is picking up something that we are otherwise unable to detect with standard tests," said the principal investigator, Dr. Mary Whooley, an associate professor of medicine at the University of California-San Francisco and a staff physician at the San Francisco VA Medical Center.
Dr. Whooley and her colleagues consider the test mainly useful in categorizing risk and organizing treatment for patients already known to have heart problems, rather than as a screening test for everyone.
"The test is not something that we should order on every patient who comes in for a routine checkup," she said.
About the protein
The protein involved -- called NT-proBNP -- is a marker in the blood for BNP, a hormone that "goes up at times of cardiac stress," Dr. Whooley said. "When the heart wall is over-expanded by too much blood volume, or damaged by lack of blood flow to the heart itself, BNP goes up," and the marker protein with it.
But "in the general population ... you get many more false-positive results than true positives, which really lowers the value of the test. It's much better at predicting risk in a population with a high incidence of heart disease."
Patients in the study had all previously experienced at least one heart-related event -- a heart attack, an artery with at least 50 percent blockage, an artery bypass or exercise-induced reduction in the blood supply to the heart. They are also part of a long-term "Heart and Soul Study" directed by Dr. Whooley designed to determine if depression is a predictor for heart disease.
Findings
The San Francisco-area patients were divided into four groups based on the level of protein marker in their blood and followed for an average of 3.7 years. During the study, 256 patients experienced an adverse cardiovascular event, including 34 who died from heart disease.
Those with the highest levels of the protein were 3.4 times more likely to suffer renewed heart or blood-vessel illness or die than patients with the lowest levels.
However, Dr. Whooley said that the test's value is limited even in heart patients, "because all of the therapies available to prevent cardiovascular events should already be used among these patients. The best it can do is identify candidates for more aggressive therapy."
Having another way to assess risks could be useful to specialists because "we know that aggressive medical management can change the negative outcomes in these patients," said Dr. Suzanne Steinbaum, a cardiologist at the Heart and Vascular Institute at Lenox Hill Hospital in New York City. She was not involved in the JAMA study.
"Having a biomarker like BNP, which clearly demonstrates those patients who are at greatest risk, will enable the clinician to know which patients need extensive diagnosis and treatment," Dr. Steinbaum said.

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