Will you be testing for CRP to assess for AMI?
September 1, 1998 3 minutes read
Will you be testing for CRP to assess for AMI?
Levels of inflammation marker could identify risk
In the pipeline may be an innovative predictor of future cardiovascular events in otherwise healthy middle-aged men - even those without common risk factors for heart problems. Authors of a new study write that their data suggest that it may be time to add an inflammation marker to the list of factors commonly used to assess cardiovascular disease risk.1 Most tests available now, however, are not sensitive enough to pick up the small differences noted in the recent research.
A blood protein known as C-reactive protein (CRP) is an acute-phase reactant - its levels increase dramatically (100-fold or more) in response to severe bacterial infection, other inflammation, or physical trauma. Adding CRP assessments to cholesterol tests, say investigators, could improve physicians' ability to predict a person's chance of having a heart attack even if he or she doesn't seem to be at risk.
Investigators from Brigham and Women's Hospital in Boston, followed more than 500 apparently healthy men participating in the large-scale (15,000-subject) Physicians' Health Study and measured baseline blood levels of CRP, total cholesterol, and HDL cholesterol for eight years. Half subsequently developed a first acute myocardial infarction (AMI), and the remainder stayed free of cardiovascular disease.
Overall, the researchers found that the more CRP a man had in his blood, the higher his risk of developing heart disease. Men with the highest levels of CRP had a threefold increase in their risk of future heart attack and a twofold increase in their risk of future stroke. This tight link strongly suggests that the immune system is involved in heart disease.
The role of CRP in predicting risk?
High blood levels of CRP and total cholesterol were each associated with significantly increased risks of future heart attack, according to study authors. Testing for CRP in addition to total cholesterol proved to be a better predictor of risk than testing for cholesterol alone. Individuals with elevated levels of both CRP and total cholesterol had a five times higher risk of a heart attack than individuals without either of those risk factors. That risk was substantially greater than the twofold increase in risk associated with elevated levels of total cholesterol alone. Moreover, elevated levels of C-reactive protein were found to predict risk of first heart attacks as many as six to eight years into the future.
Increased levels of C-reactive protein were not linked to risks of venous thrombosis. This finding is critical since, in contrast to heart attacks and strokes, these venous blood clots typically are not linked to atherosclerosis
This latest finding might be particularly helpful when patients do not have many of the common risk factors for heart attack - cigarette smoking, high blood cholesterol, high blood pressure, and physical inactivity. Researchers have known for some time that heart attacks often occur in people at apparently low risk.
"We believe that between one-third and one-half of all people who ultimately have a heart attack don't have three or four traditional risk factors," wrote lead author Paul M. Ridker, MD, of the division of preventive medicine at Brigham and Women's. "Such patients may believe they are at low to moderate risk based on a cholesterol profile."
The investigator went on to say that the fact that markers of inflammation such as CRP are proving to be potent predictors of risk of future heart attack raises the possibility that there may be novel pathways of cardiovascular treatment and prevention directed at the inflammatory process.
Last year, researchers found that the benefit of preventive aspirin therapy was greatest among those with the highest levels of underlying inflammation. Because aspirin is an anti-inflammatory as well as a blood-thinning agent, these data suggest that other anti-inflammatory therapies may also help in preventing and treating heart disease.
Reference
1. Ridker PM, Glynn RJ, Hennekens CH. C-reactive protein adds to the predictive value of total and HDL cholesterol in determining risk of first myocardial infarction. Circulation 1998;97:528-534.
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