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What Is CRP (C-Reactive Protein)?

Detects Acute Inflammation

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Updated April 08, 2014

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

CRP, also known as C-Reactive Protein, is a test which measures the concentration in blood serum of a special type of protein produced in the liver which is present during episodes of acute inflammation or infection. In the body, CRP plays the important role of interacting with the complement system, an immunologic defense mechanism.

An elevated CRP test result is an indication of acute inflammation. In cases of inflammatory rheumatic diseases, such as rheumatoid arthritis and lupus, doctors can utilize the CRP test to assess the effectiveness of a specific arthritis treatment and monitor periods of disease flare-up. It's value is as a general indicator though, not specific. By "not specific", I mean that the CRP test does not reveal what is causing inflammation in the body -- it simply indicates that there is inflammation.

With known cases of inflammatory disease, such as rheumatoid arthritis and lupus, a low CRP level is possible. Normally there is little CRP in blood serum. From Lab Tests Online, "A high or increasing amount of CRP in the blood suggests the presence of inflammation but will not identify its location or the condition causing it. In individuals suspected of having a serious bacterial infection, a high CRP suggests the presence of one. In people with chronic inflammatory conditions, high levels of CRP suggest a flare-up or that treatment has not been effective. If the CRP level is initially elevated and drops, then it means that the inflammation or infection is subsiding and/or responding to treatment."

A positive CRP may occur with several diseases and conditions, including:

A positive CRP also can be detected during the last half of pregnancy or with the use of oral contraception.

Sedimentation Rate Is Another Test for Inflammation

Another blood test often ordered in conjunction with CRP is known as ESR (erythrocyte sedimentation rate or sedrate). Both CRP and ESR give similarly non-specific information about  inflammation. CRP appears and disappears more quickly than changes in ESR. Therefore, your CRP level may drop to normal following successful treatment, whereas ESR may remain elevated for a longer period.

CRP and Heart Disease

Studies have indicated that CRP may be elevated in heart attacks. It is yet to be determined if CRP serves as a marker of heart disease or whether it plays a part in causing atherosclerotic disease (hardening of the arteries).

There is also a high sensitivity CRP test (hs-CRP) in addition to the regular CRP test. The hs-CRP measures very low amounts of CRP in the blood and is typically used to assess risk for heart problems.

Source:

C-Reactive Protein. The Test. Lab Tests Online. July 12, 2012
http://labtestsonline.org/understanding/analytes/crp/tab/test

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