Molecule Test May Be Heart Disease Detection Key

Testing blood for amounts of a small molecule called C-reactive protein may be a better predictor of heart disease than the current method of testing cholesterol, a study of nearly 28,000 women has found.

The report, published today in the New England Journal of Medicine, is the largest yet to find such a link and is likely to influence national guidelines for monitoring heart disease risk, which are currently under review.

Heart specialists reacted enthusiastically to the study. If an inexpensive test for the C-reactive protein marker became routine, they said, it might help identify millions of people whose cholesterol levels are considered normal but are still at high risk for heart attacks and strokes. Using both protein and cholesterol screening could become a potent tool in fighting heart disease.

“If you add the two markers together you get a much better mousetrap for predicting risk,” said Dr. Paul M. Ridker, lead author of the study and a professor of medicine at Harvard University and a cardiologist at Brigham and Women’s Hospital in Boston.

Prior studies had indicated that levels of C-reactive protein correlates with heart disease risk in men and women, but this study adds clout because of its large number of subjects.

The study enrolled 27,939 healthy American women aged 45 and older. At the start of the test, blood levels of LDL cholesterol -- the so-called bad cholesterol -- and C-reactive protein were obtained. Eight years later, medical records were examined for incidences of heart attacks and strokes. Medical procedures to clear blocked blood vessels were also noted.

The scientists found that women with elevated C-reactive protein levels -- regardless of their cholesterol levels -- were at heightened risk for heart attack or stroke. The higher the C-reactive protein, the greater the risk. The risk of a heart attack or stroke was highest when both cholesterol and C-reactive protein levels were elevated, the study found.

C-reactive protein is released by the liver and the linings of blood vessels when they are inflamed. Inflammation is thought to trigger the plaque on vessel walls to rupture and form clots, which then block the vessels and trigger a heart attack or stroke.

Different levels of inflammation could help explain why one person with plaque buildup has a heart attack yet another person with similar buildup does not.

Ridker estimates that perhaps 25% of the U.S. population have elevated C-reactive protein levels but have normal cholesterol levels.

Dr. Sidney Smith, chief science officer of the American Heart Assn. and a professor of medicine at the University of North Carolina in Chapel Hill, said, “The test could indicate to people that their risk is higher than they thought. It could be a very helpful, motivating factor” for altering their lifestyle.

Scientists cautioned that it is premature to prescribe drugs such as statins or aspirin to people with high C-reactive protein levels, but normal cholesterol. There is no evidence yet that such treatment would be helpful.

A panel of experts from the American Heart Assn. and the Centers for Disease Control and Prevention is considering C-reactive protein screening as a part of heart disease prevention. Its recommendations are scheduled for release this year.

“Hopefully, we can start using C-reactive protein as a cardiological screening test just like cholesterol,” said Dr. Gerald M. Pohost, chief of the division of cardiovascular medicine at USC’s Keck School of Medicine.

Dr. Robert O. Bonow, president of the American Heart Assn. and chief of cardiology at Northwestern University Medical School, said the protein marker findings are exciting, but added that they should not distract doctors and patients from combating established risk factors, such as smoking.

“A large number of people have high blood pressure and don’t know it -- or do and aren’t being treated,” he said. “People are gaining weight instead of losing weight. We need to continue to focus on getting the message out about things we know about already.”