Like the erythrocyte sedimentation rate, the C-reactive protein (CRP) test measures inflammation. However, CRP usually changes more rapidly than ESR because it is made by the liver and secreted hours after the beginning of infection or inflammation. CRP plays a part in your immune response by interacting with your body’s complement system. The CRP is non-specific, meaning it cannot give your doctor information about where inflammation is occurring in your body. However, the amount of CRP can give an idea as to the degree of inflammation your body is experiencing, and it is used by doctors in lupus treatment to monitor flares and to assess how well your medications are working. It is important to realize, though, that a low CRP value does not necessarily mean that an individual is experiencing no inflammation; a low CRP can be seen in lupus patients with active inflammation. An elevated CRP can also be seen after someone has a heart attack, surgical procedure, or infection.
High Sensitivity C-Reactive Protein (HS CRP)
In apparently healthy individuals, studies have shown that C-reactive protein (CRP) can be an indicator of the risk of cardiovascular disease (CVD), since certain types of CVD, namely atherosclerosis, are known to involve inflammation. A high sensitivity test (high sensitivity C-reactive protein, or HS CRP) is used to evaluate this risk, because the level of CRP in the blood is low. The high sensitivity CRP is important because studies have shown that lupus patients have higher levels of atherosclerosis than the general population. However, the HS CRP can reflect many things in lupus patients besides lupus activity and/or one’s risk of heart attack.
For the HS CRP test, blood is taken from a vein in your arm and mixed with a substance called an antiserum. The antiserum contains a specific substance that is able to detect the CRP. The American Heart Association and Centers for Disease Control and prevention maintain that a high-sensitivity CRP of less than 1.0 mg/L suggests a low risk for CVD, 1.0-3.0 mg/L suggests an average risk, and a CRP above 3.0 mg/L suggests a high risk.
- “C-Reactive Protein.” Lab Tests Online. 29 April 2009. American Association for Clinical Chemistry. 12 July 2009 <http://labtestsonline.org/understanding/analytes/crp/test.html>.
- “Inflammation, Heart Disease and Stroke: The Role of C-Reactive Protein.” American Heart Association. 12 July 2009. <http://www.americanheart.org/presenter.jhtml?identifier=4648>.
- “Hs-CRP.” Lab Tests Online. 8 April 2009. American Association for Clinical Chemistry. 12 July 2009. <http://labtestsonline.org/understanding/analytes/hscrp/test.html>.