NBC Nightly News recently featured a story about C-reactive protein as a “simple blood test that could save women’s lives.” As WebMD’s medical expert on cholesterol and a heart surgeon, I want to explain the role of C-reactive protein as a so-called biomarker of heart disease. While the use of this blood test may be useful in helping to determine one’s risk of a possible heart attack or a stroke in the future, it is simply one of many new and emerging biomarkers that your doctor can use to help determine your risk.
C-reactive protein (CRP) is found in the blood. Its levels rise in response to inflammation. The more inflammation, the higher the CRP.
Now lets talk about inflammation and its role as a cause of events like heart attacks and stroke. It’s been well documented that both inflammation throughout the body as well as inflammation specific to the blood vessels play a prominent role in events leading to the build up and rupture of plaques in a person’s arteries. Exactly how this occurs is under great debate and being widely studied.
While CRP and its role in inflammation was discovered in the 1930s, it has received more attention in medical journals and in the media over the past 10 years. At some points, experts thought CRP was a more important test that the traditional cholesterol panel that looks at levels of good and bad cholesterol. They also thought that CRP testing alone was a better indicator than measuring LDL-C (the bad cholesterol) in predicting heart attacks and strokes.
More than 25 studies published during the last 10 years have provided strong evidence that C-reactive protein predicts heart risk in various scenarios, not only in initially healthy subjects, but also in those who have established atherosclerosis (clogging of the arteries). However, two years ago, in July 2009, The Journal of the American Medical Association analyzed data from approximately 100,000 people and concluded high levels of C-reactive protein does not cause heart disease.
Researchers have also found out that lowering C-reactive protein does not protect people from developing heart disease. Many patients who had “low cholesterol” but had high CRP were treated with statin drug therapy to try to lower CRP. It was hoped that this would lower the rate of heart attacks and strokes. As of today, we do know that lowering CRP has not altered the rate of strokes or heart attacks.
A large study authored by more than 35 noted MDs and PhDs showed there are people who produce more C-reactive protein throughout their lives and others who produce less. The theory goes, if C-reactive protein causes heart disease, those who make more would have more heart disease. The study did not find this. There was no association between CRP and heart disease rate. So, in other words, the association between C-reactive protein and heart disease must reflect something else. In short, C-reactive protein is simply a marker of inflammation and NOT an accurate predictive test for heart disease risk.
The U.S. Preventive Services Task Force announced recently supported this finding, saying that CRP alone was not enough to determine heart disease risk.
Every day I have patients who read news articles, or see news stories on a new test. Many are now asking about their C-reactive protein. Thanks to misleading and often half researched news articles and reports, many think that this single test is absolutely critical to prevent a heart attack. I explain to them, as I have done here, that while it is important, it is only one biomarker used to help determine their risk. Despite multiple attempts to develop drugs to target and lower C-reactive protein, many experts now feel that it is time to abandon that search and concentrate on finding better drugs to prevent the build up of cholesterol in the artery wall.