Heart disease is the #1 cause of death for both men and women, not only in the U.S., but worldwide. Research for cardiovascular disease (CVD), which also costs the economy millions in lost productivity and hospital bills, is heavily funded (about $2 billion in public funds in the U.S. annually)1. Consequently, researchers are discovering new information about how to determine if people are at risk for CVD, which often manifests as coronary artery disease. To the list of risk factors that we know of (high cholesterol, obesity, diabetes, high blood pressure, lack of exercise, family history of cardiovascular disease, and smoking), another potential indicator has been added: elevated C-Reactive protein (CRP) in the blood.
C-Reactive protein (CRP) is a protein that was discovered by doctors over 70 years ago. Generated as part of the body's immune response, CRP levels increase in the blood when there is injury or inflammation somewhere in the body. Doctors have used C-reactive protein tests for years to monitor their patients with lupus, rheumatoid arthritis, and many other conditions that involve the body's immune system.2
C-Reactive protein has been linked by many studies to atherosclerosis, which is when plaque builds up in the arteries. This plaque can impede blood flow through the artery or break off and cause dangerous blood clots to form. Plaque can build up in many areas of the body: in the coronary arteries (causing heart disease), in the carotid arteries (affecting blood flow to the brain), or in the arteries of the arms and legs (causing peripheral artery disease). When plaque forms in the arteries, it does not simply form there, it causes injury to the arteries, generating an inflammatory response, causing the body to release C-Reactive protein into the blood. Along with cholesterol levels, blood pressure, glucose levels, and other screening tests, elevated CRP levels can be an additional indication that someone is at higher risk for cardiovascular disease.
Many studies, including one in the November 14, 2002 New England Journal of Medicine, concluded that CRP outperforms LDL cholesterol as a predictor of cardiovascular risk. In addition, the researchers discovered that CRP identifies a different high-risk group from LDL, so the tests complement each other to provide a better overall indication of risk for heart disease.2
CRP testing has become more sophisticated, and with good reason. Inflammation in the arteries elevates CRP levels in the blood, but not a lot. Consequently, High Sensitivity C-Reactive Protein (hsCRP) screening is needed to detect these small changes in CRP levels. Results from the hsCRP test are reported in three levels:
- <1 milligram of CRP/liter of blood (mg/L) = low risk
- 1 to 3 mg/L = average risk
- 3> mg/L = high risk
If your doctor doesn't order a test for hsCRP for you, it's probably because his or her advice for lowering your risk for heart disease wouldn't change much based on the results. Statin medications, exercise, and weight loss (especially around the belly) all lower the CRP levels in the blood, much like they do for LDL cholesterol. So when your doctor advises you to lose weight, exercise more, and stay on your statins, he/she knows that it will positively impact all of your risk factors for developing cardiovascular disease, including lowering your CRP levels.
Many conditions can cause CRP levels to increase, including acute infections like pneumonia, rheumatoid arthritis and other autoimmune diseases, and even cancer. CRP levels also increase as people age. There are currently no drug treatments that specifically lower CRP levels.
For the reasons outlined above, C-Reactive Protein testing isn't medically appropriate for people who have already been diagnosed with cardiovascular disease and are being treated for that. It is most appropriate for people who may have a family history of heart attack, stroke, or other risk factors who want another valuable piece of information to assess their risk for cardiovascular disease. A conversation with one's doctor can provide guidance on the value of an hsCRP test based on current health and other biometrics already measured.
1 CardioBuzz: More Money Needed for Heart Research?, January 28, 2014, MedPage Today®, https://www.medpagetoday.com/blogs/cardiobuzz/44015
2 C-Reactive Protein Test to Screen for Heart Disease, Harvard Health Publishing, Harvard Medical School, March 21, 2017, https://www.health.harvard.edu/heart-health/c-reactive-protein-test-to-screen-for-heart-disease