Stop 10 people on the street, and chances are many of them already know of the link between high cholesterol and cardiovascular disease. They may even know their own cholesterol level. But ask those same people whether their C-reactive protein level is normal, and you'll probably get lots of blank stares.
Those stares notwithstanding, links between C-reactive protein (CRP) -- a substance produced by the body in response to inflammation -- and cardiovascular disease have increasingly been recognized in scientific circles.
A November New England Journal of Medicine article reported that in an eight-year study of almost 28,000 women, high levels of CRP were actually a more reliable indicator of risk for cardiovascular problems like heart attack and stroke than elevated cholesterol. People with low cholesterol but high CRP levels were shown to be at greater risk than those in the opposite situation.
But CRP has only recently captured the mainstream media's attention. A November U.S. News & World Report cover story touted CRP tests as something that could "save the lives of millions who don't even know they're in danger." Men's Health alerted readers to "the new heart alarm."
"Cholesterol is old news and CRP is newsworthy, new stuff, so it does have the public's interest," says cardiologist Dr. Michael Rubinstein, director of Cardiac Prevention at Union Memorial Hospital.
With cardiovascular diseases the No. 1 killer of American men and women, many patients were eager to get tested. Could inflammation -- a hot topic in many fields of medicine right now -- be the missing link that explains why so many people with impeccably healthy lifestyles and no known risk factors still have unexpected heart attacks?
Findings still unclear
The answer is a resounding maybe. The problem is that while the CRP link was undeniably intriguing, doctors lacked concrete guidelines on just who should be tested, how to interpret the findings and how to translate those findings into an appropriate treatment program.
In January, a joint panel convened by the American Heart Association and the Centers for Disease Control issued its recommendations on CRP testing. The guidelines were conservative, rejecting the idea of routine screening for the entire adult population. CRP testing was indicated only for those already at minimally elevated risk of cardiovascular disease -- and even then, testing is still optional; high CRP levels found in an otherwise borderline patient can be used to tip the scales toward more aggressive treatment.
"In patients who have some cardiac risk, like diabetes, hypertension, smoking, family history or borderline elevated cholesterol, I'll use CRP in a sense as a tiebreaker," says Rubinstein. "I just haven't seen it as a marker that warrants treatment in and of itself."
That might soon change. A multi-year study of 15,000 men and women with optimal cholesterol but elevated CRP is getting under way to determine whether lowering CRP levels with drugs called statins will in fact reduce the number of heart attacks and strokes.
Facts about CRP
Meanwhile, here's what you need to know about CRP.
* C-reactive protein is a substance produced by the body in response to inflammation caused by anything from a sinus infection to arthritis. Elevated CRP simply says, "There's some inflammation somewhere," Rubinstein explains.
* How is CRP linked to heart disease? There is growing evidence that atherosclerosis, the buildup of fatty deposits in artery linings, is actually an inflammatory process.
* Who should get tested? People with a 10 percent to 20 percent risk of heart disease in the next 10 years might benefit from the test. Those already determined to be at high risk (20 percent) because of other factors should already be getting intensive treatment, regardless of CRP levels. (To calculate your risk, visit the heart association's Web site at www.americanheart.org.)
* CRP testing requires nothing more than a blood sample. The cost can vary from $15 to $120; check with your insurance provider about whether you are covered.
* What do the results mean? CRP levels greater than 3 milligrams per liter are considered high. In assessing CRP's link to possible cardiovascular issues, doctors need to rule out other causes of elevated CRP, like acute infection, trauma or chronic inflammatory conditions like arthritis. Women on hormone replacement therapy also tend to have high CRP.
* Regardless of your CRP levels, experts urge everyone to identify and control the already well-established risk factors for cardiovascular disease: quit smoking, control high blood pressure and diabetes, exercise regularly and eat a diet low in saturated fat and cholesterol.
* Still confused? Talk to your doctor.
What tests to expect