The acronym CRP stands for C-reactive protein, a non-specific marker (a substance that may indicate disease) that is measured by blood tests. It is produced by the liver and increases during episodes of acute systemic inflammation. A number of studies have suggested that CRP levels might be an indication of an individual's risk for heart disease and that, overall, inflammation plays an important role in the development of cardiovascular disease. However, in evaluating cardiac risk, physicians look at a very narrow range of CRP levels (from zero to 3.0 and above). This requires a special test called high sensitivity CRP (hs-CRP), which may be able to reveal inflammation going on at the micro-vascular level. If this test shows that your CRP is less than 1.0 mg per liter of blood, your risk of heart disease is considered low; if it is between 1.0 and 3.0, your risk is average; if it is above 3.0, your risk is high.
People who have arthritic conditions tend to have high CRP levels because inflammation underlies these disorders. Arthritis may push test results far beyond the range used to assess heart disease risk. In fact, when inflammation levels are being assessed in patients with rheumatoid arthritis, inflammatory bowel disease or other autoimmune conditions, the hs-CRP test is not used. Instead, inflammation is evaluated with a test that measures levels in excess of 10 mg/L. Most active infections and inflammatory processes result in CRP levels above 100 mg/L. Under these circumstances, CRP is used to follow the trend. When CRP drops, inflammation is decreasing. As far as checking for these conditions is concerned, a CRP level of 10 mg/L or lower is considered "normal."
Because inflammation levels can be quite high in people with autoimmune diseases, the hs-CRP test simply isn't useful for assessing their cardiovascular risk. But the inflammation that underlies rheumatoid arthritis does appear to increase the risk of cardiovascular disease and death. A study from the Mayo Clinic included 603 patients with rheumatoid arthritis found a higher risk of death from cardiovascular disease among them even after accounting for such factors as a history of heart disease, high blood pressure, diabetes, cancer and alcoholism. The study was published in the March, 2005, issue of Arthritis and Rheumatism.
Because an hs-CRP test isn't useful to assess cardiovascular risk among people with inflammatory diseases, these patients have to rely on such well-recognized risk factors as high blood pressure or high cholesterol, whether or not they smoke, their weight and their risk of diabetes. In addition to such standard measures for reducing the risk of cardiovascular disease as exercise, keeping weight under control, practicing stress reduction techniques and getting adequate sleep, I recommend that people with these disorders make an effort to reduce inflammation and their risk of heart disease by following an anti-inflammatory diet.
Andrew Weil, M.D.