MONDAY, Feb. 16, 2004 (HealthDayNews) -- Researchers are reporting a new molecular marker that can help doctors assess the risk of heart attack, stroke and other cardiovascular diseases.
It is a protein called serum amyloid A (SAA), which is associated with the inflammation that has emerged recently as a leading factor in cardiovascular disease.
A new study shows SAA is as useful an indicator of risk as the best-known inflammation marker, C-reactive protein (CRP), says study leader B. Delia Johnson, an epidemiologist and research assistant at the University of Pittsburgh Graduate School of Public Health.
"It is better only in the sense that it is actually related to already present coronary artery disease, where CRP isn't," Johnson says. "What still needs to be explored is just how useful it is in respect to CRP. Both are excellent indicators of outcome."
That conclusion comes from the Women's Ischemia Syndrome Evaluation study, and the findings appear in the Feb. 17 issue of Circulation. Ischemia is the blockage of arteries that can lead to heart attack, stroke, heart failure and other cardiovascular problems.
Johnson and her colleagues looked at the relationship between blood levels of CRP and SAA in 705 women enrolled in the study. All were referred for angiography, a technique that gives images of the arteries in persons suspected to be at risk of cardiovascular problems because they experienced possibly dangerous chest pain.
In a three-year follow-up, the risk of a cardiovascular event such as a heart attack, congestive heart failure or stroke increased by 3.2 percent for each increase of 1 milligram per deciliter of SAA.
A similar relationship was found for blood levels of CRP. But the SAA levels were more strongly related to the presence of existing artery disease.
Many more studies are needed to determine whether and how SAA readings might be used in medical practice, Johnson says. One complication is that SAA is a marker not only of coronary artery disease but also of inflammatory conditions such as rheumatoid arthritis.
And it is possible that the results of the study in women might not be directly applicable to men, Johnson adds, because there is a difference in how heart disease affects each of the sexes.
"Women who have chest pain and are referred for angiography are less likely to be subject to heart disease than men," she says. "Fewer than 50 percent of them have heart disease, whereas men are much more likely to have heart disease."
The study is an important addition to knowledge about SAA because it addresses the different meaning it may have in men and in women, says Dr. Richard C. Becker, a spokesman for the American Heart Association.
Becker, a professor of medicine at the Duke University School of Medicine, has an interest in the molecular activity of SAA. It binds to HDL cholesterol, normally the "good" kind that helps keep arteries clear of deposits, and alters it so that it begins to attack artery walls, he explains.
"If we can take some of the biology and put it into a working context, for me that opens up a very exciting area," he adds. "At least we can understand such markers better and be able to assess their use in clinical care. Certainly we are getting close to that with CRP."