Ask an Expert: C-reactive Protein (CRP) Testing

Q: I read in the news recently about a blood test involving C-reactive protein that can predict your risk of heart disease.  How does this test differ from cholesterol screening?  Should I ask my doctor to give me this test when I go for my next physical?

Answer from Dr. Craig Walsh, cardiologist with Columbia Cardiology Associates and the Providence Heart and Vascular Institute, and Dr. Andrew Carter, director of interventional cardiology research for Providence Heart and Vascular Institute: 

C-reactive protein, or CRP, is a substance found in the blood when active inflammation is present in the body. Inflammation occurs when the body dispatches immune cells to fight infections and other perceived health threats. While normally a protective process, inflammation can sometimes step into high gear and cause complications. Rheumatoid arthritis, for example, is a disease marked by excessive inflammation and elevated CRP levels in the blood.

Preliminary research now indicates that inflammation may also play a role in the development of heart disease. Evidence gathered to date suggests that atherosclerosis, the buildup of fatty plaque in an artery, prompts an inflammatory response from the body. Inflammation settles in the artery and can cause the plaque to rupture, producing clots that can block blood flow and, in some cases, lead to a heart attack. Elevated CRP levels in the blood can flag health care providers to the presence of this inflammation and potential risk for heart attack.

While more study is needed, it appears CRP tests can complement cholesterol tests and other established measures used to assess a person’s risk of developing heart disease. Cholesterol is one of the primary substances found in plaque. Elevated cholesterol levels are associated with plaque buildup and increased risk of heart attack, so routine monitoring is recommended. CRP tests, by measuring active inflammation, may show how prone a plaque is to rupture. Together, cholesterol and CRP can provide important information about your heart attack risk and the best means of prevention.

CRP testing is not recommended for everyone. Those scoring low on traditional risk assessment tools for heart disease (which weigh cholesterol levels, blood pressure, cigarette smoking and other factors) are unlikely to benefit from CRP testing. Those who have already experienced a stroke or heart attack, or are known to be at high risk for such events (e.g., individuals with diabetes), should be on a treatment plan for heart disease regardless of their CRP levels. 

The best candidates for CRP testing are people who are at moderate risk, meaning they have not yet been treated for heart disease but do have high cholesterol, high blood pressure or other established risk factors. Elevated CRP levels (greater than 3.0 mg/L) in such individuals might indicate the need for treatment to help prevent a heart attack. The prescribed course of action could include dietary changes, exercise plans, smoking cessation and, possibly, statin drugs. The lifestyle modifications and medications used to reduce cholesterol levels also lower CRP levels, so no special measures are needed to treat CRP.