Cardiac markers are biomarkers measured to evaluate heart function. They can be useful in the early prediction or diagnosis of disease. Although they are often discussed in the context of myocardial infarction, other conditions can lead to an elevation in cardiac marker level.
C-reactive protein (CRP) is a substance produced by the liver in response to inflammation. Other names for CRP are high-sensitivity C-reactive protein (hs-CRP) and ultra-sensitive C-reactive protein (us-CRP). A high level of CRP in the blood is a marker of inflammation. It can be caused by a wide variety of conditions, from infection to cancer. High CRP levels can also indicate that there’s inflammation in the arteries of the heart, which can mean a higher risk of heart attack. However, the CRP test is an extremely nonspecific test, and CRP levels can be elevated in any inflammatory condition.
Most of the early markers identified were enzymes, and as a result, the term “cardiac enzymes" is sometimes used. However, not all of the markers currently used are enzymes. For example, in formal usage, troponin would not be listed as a cardiac enzyme.
Individuals with CRP levels greater than or equal to 2 milligrams per litter (mg/L) likely need more intense management and treatment for heart disease. Elevated levels of CRP may have an important role in identifying those who might need closer follow-up or more intensive treatment after heart attacks or heart procedures. CRP levels may also be useful in uncovering those at risk of heart disease where cholesterol levels alone may not be helpful. The Centres for Disease Control and Prevention Trusted Source considers these conditions significant risk factors for developing heart disease:
- high blood pressure
- high cholesterol
- unhealthful diet
- limited physical activity
- alcohol use in excess
- being overweight
How to Identify?
Doctors don’t all agree on the implications of high CRP levels. Some believe there’s a correlation between high CRP levels and an increased likelihood for heart attack or stroke. The Physicians’ Health Study found that among healthy adult men, those with a high level of CRP were three times more likely to have a heart attack than those with low levels of CRP. This was among men who had no previous history of heart disease. High cholesterol is a more commonly cited risk factor. Doctors may also order a CRP test to diagnose inflammatory autoimmune diseases, including:
- inflammatory bowel disease (IBD)
- rheumatoid arthritis
This is a routine test with low risk, but there’s a slight chance of the following complications from the blood draw:
- excessive bleeding
- dizziness or light-headedness
- bruising or infection at the puncture site
A CRP test can be helpful in assessing a person’s risk of heart disease, especially in combination with high cholesterol levels. The benefits of this test outweigh potential complications, especially for those at risk of heart disease or stroke and those recovering from recent heart procedures.
What to Do?
C-reactive protein is measured in milligrams of CRP per liter of blood (mg/L). In general, a low C-reactive protein level is better than a high one, because it indicates less inflammation in the body. A reading of less than 1 mg/L indicates you’re at low risk of cardiovascular disease. A reading between 1 and 2.9 mg/L means you’re at intermediate risk. A reading greater than 3 mg/L means you’re at high risk of cardiovascular disease. A reading above 10 mg/L may signal a need for further testing to determine the cause of such significant inflammation in your body. This especially high reading may indicate:
- a bone infection, or osteomyelitis
- an autoimmune arthritis flare-up
- lupus, connective tissue disease, or other autoimmune diseases
- cancer, especially lymphoma
- pneumonia or other significant infection