High levels of C-reactive protein indicate early heart disease
Using a simple, inexpensive test to determine levels of C-reactive protein in the blood, researchers were able to detect heart disease before symptoms were apparent, according to a report in todays rapid access issue of Circulation: Journal of the American Heart Association.
Researchers studied the relationship between levels of C-reactive protein (CRP, a marker of inflammation in the body), and coronary calcium, which indicates the extent of atherosclerosis in the coronary arteries. Atherosclerosis, or fatty build-up in the arteries, is a sign of heart disease.
"While the majority of men and women in our study had some calcium in their arteries, the higher the C-reactive protein level, the more calcium they had," says Thomas J. Wang, M.D., lead author of the study and research fellow with the National Heart, Lung, and Blood Institutes Framingham Heart Study.
Researchers studied 321 people (average age 60) who have participated in the Framingham Heart Study since 1971. They underwent blood tests to determine CRP levels and electron beam computed tomography scans to detect the amount of calcium in their coronary arteries, which is given as a coronary artery calcification (CAC) score.
Participants were divided into five groups, or quintiles, based on their CRP levels. Quintile ranges for CRP were 0-0.04 mg/dL, 0.1-0.8 mg/dL, 0.9- 2.3 mg/dL, 2.4-6.5 mg/dL, and 6.7-48.2 mg/dL. For both men and women, average CAC scores increased with higher levels of CRP.
People with elevated CRP seemed to have or develop more coronary calcium, even after adjusting for age, traditional risk factors and Framingham risk score.
"It has been known that inflammation plays a role in coronary artery disease but the direct link between the level of this marker of inflammation and the actual presence of calcium in the coronary arteries is a new finding," Wang says.
A study limitation was that CRP levels were obtained four to eight years before the imaging scans, which may have blurred the link between atherosclerosis and CRP, says Wang. Future studies should clarify how best to combine the information from CRP tests, imaging studies, and knowledge of traditional risk factors such as high blood pressure, cholesterol and smoking.
Co-authors include Martin G. Larson, Sc.D.; Daniel Levy, M.D.; Emelia J. Benjamin, M.D., Sc.M.; Michelle J. Kupka, M.A.; Warren J. Manning, M.D.; Melvin E. Clouse, M.D.; Ralph B. DAgostino, Ph.D.; Peter W.F. Wilson, M.D.; and Christopher J. ODonnell, M.D., M.P.H.
This study was funded in part by the National Institutes of Health.
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