But there's a lesser-known, relatively new player in heart-disease risk assessment called CRP, or C-reactive protein. A study in the January 2004 issue of The New England Journal of Medicine suggested that elevated levels of CRP could provide doctors with information that could ultimately prevent thousands of deaths from heart disease. But many reports have said that knowing CRP levels provides no clinical benefit whatsoever, making the whole subject a source of controversy.
Atherosclerosis -- hardening and narrowing of the arteries -- gets a lot of bad press but with good reason. This progressive process silently and slowly blocks arteries, putting blood flow at risk.
Atherosclerosis is the usual cause of heart attacks, strokes, and peripheral vascular disease -- what together are called "cardiovascular disease." Cardiovascular disease is the No. 1 killer in America, with more than 800,000 deaths in 2005.
How does atherosclerosis develop? Who gets it, and...
The blood test for CRP indicates inflammation, which studies have shown to be critical in the development of atherosclerosis, or plaque build-up in the blood vessel walls.
According to the American Heart Association and the CDC, a CRP level of less than 1 mg per liter indicates a low risk of cardiovascular disease; 1-3 mg/L indicates moderate risk, and greater than 3 mg/L equals high risk.
But while the test itself is simple, its implications can be confusing.
"I don't think anybody disputes that inflammation plays an important role in artherosclerosis and its complications," says P.K. Shah, MD, director of cardiology at Cedars-Sinai Medical Center. "But the incremental value of CRP as a risk factor above all the conventional risk factors is relatively small. This is the biggest bugaboo about CRP -- we don't know what to do with the information."
One problem with the CRP test is that it's not specific, so levels can be elevated due to other sources of inflammation besides artherosclerosis, such as gum disease or a viral infection. (For this reason, if you do want to be tested for CRP, doctors recommend waiting if you have an acute infection.)
Another issue is what exactly a patient should do if he is found to have a high CRP level. Lowering CRP levels doesn't necessarily reduce risk of heart disease.