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C-Reactive Protein
Este artigo foi revisto pela última vez em
Este artigo foi modificado pela última vez em 10 de Julho de 2017.
At a Glance
Why Get Tested?
To identify the presence of inflammation and to monitor response to treatment [Note: to test for your risk of heart disease, a more sensitive test (hs-CRP) is used.]
When To Get Tested?
When your doctor suspects that you might be suffering from an inflammatory disorder (as with certain types of arthritis and autoimmune disorders or inflammatory bowel disease) or to check for the presence of infection (especially after surgery)
Sample Required?
A blood sample taken from a vein in your arm
What is being tested?
C-reactive protein (CRP) is an acute phase reactant, a substance made by the liver and secreted into the bloodstream within a few hours after the start of an infection or inflammation. Increased levels are observed after a heart attack, in sepsis, and after a surgical procedure. Its rise in the blood can also precede pain, fever, or other clinical indicators. The level of CRP can jump a thousand-fold in response to inflammation and can be valuable in monitoring disease activity.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in your arm.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.
Accordion Title
Common Questions
  • How is it used?
    The CRP test is useful in assessing patients with:

    CRP may be used to screen apparently healthy people for the following conditions. However, in these cases, the more sensitive test hs-CRP will be ordered:

    While the CRP test is not specific enough to diagnose a particular disease, it does serve as a general marker for infection and inflammation, thus alerting medical professionals that further testing and treatment may be necessary.

  • When is it ordered?
    Because CRP increases in severe cases of inflammation, the test is ordered when acute inflammation is a risk (such as from an infection after surgery) or suspected based on patient symptoms. It is also ordered to help evaluate conditions such as rheumatoid arthritis and lupus and is often repeated to determine whether treatment is effective. This is particularly useful for inflammation problems since CRP levels drop as inflammation subsides.

    CRP also is used to monitor wound healing and to monitor patients who have surgical cuts (incisions), organ transplants, or burns as an early detection system for possible infections.

  • What does the test result mean?
    A high or increasing amount of CRP in your blood suggests that you have an acute infection or inflammation.

    If the CRP level in your blood drops, it means that you are getting better and inflammation is being reduced.


  • Is there anything else I should know?
    CRP levels can be elevated in the later stages of pregnancy as well as with use of birth control pills or hormone replacement therapy (i.e., estrogen). Higher levels of CRP have also been observed in the obese.

    Another test to monitor inflammation is called the erythrocyte sedimentation rate (ESR). Both tests are elevated in the presence of inflammation; however, CRP appears and then disappears sooner than changes in the ESR. Thus, your CRP level may fall to normal if you have been treated successfully, such as for a flare-up of arthritis, but your ESR may still be abnormal for a while longer.

  • What are chronic inflammatory diseases?
    "Chronic inflammatory diseases" is a non-specific term used to characterize long-lasting or frequently recurring bouts of inflammation as associated with a more specific disease. This can be caused by a number of different pathological conditions such as arthritis, lupus, or inflammatory bowel disease (Crohn’s disease).
  • What is the difference between regular CRP and hs-CRP tests?
    Both tests measure the same molecule in the blood. The high sensitivity CRP (hs-CRP) test measures very small amounts of CRP in the blood and is ordered most frequently for seemingly healthy people to assess their potential risk for heart problems. It measures CRP in the range from 0.5 to 10 mg/L. The regular CRP test is ordered for patients at risk for infections or chronic inflammatory diseases (see Question #1). It measures CRP in the range from 10 to 1000 mg/L.
View Sources
Sources Used in Current Review

Wu, A. (2006). Tietz Clinical Guide to Laboratory Tests, Fourth Edition. Saunders Elsevier, St. Louis, Missouri. Pp 190-193.

Sources Used in Previous Reviews
A Manual of Laboratory & Diagnostic Tests. 6th ed. Fischbach F, ed. Philadelphia: Lippincott Williams & Wilkins; 2000: 619-620.

MEDLINEplus Medical Encyclopedia: C-reactive protein. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003356.htm

Nader Rifai, PhD. Department of Laboratory Medicine, Children's Hospital, Boston, MA.