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| Definition: |
C-reactive protein is a test that measures the concentration of a protein in serum that indicates acute inflammation.
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| How the test is performed: |
Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and a tourniquet (an elastic band) or blood pressure cuff is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the tourniquet to distend (fill with blood). A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the tourniquet is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.
CRP is detected with the use of antiserum (serum that contains antibodies for a particular antigen) in several tests that measure the protein and protein-bound molecules. |
| How to prepare for the test: |
| No preparation is necessary for this test. |
| How the test will feel: |
| When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing. |
| Why the test is performed: |
C-reactive protein is a special type of protein produced by the liver that is only present during episodes of acute inflammation. The most important role of CRP is its interaction with the complement system, which is one of the body's immunologic defense mechanisms.
While this is not a specific test, it does give a general indication of acute inflammation. Your health care provider might use this test to check for rheumatoid arthritis or rheumatic fever exacerbations. The test might also be useful to monitor response to therapy. |
| Normal Values: |
| Normally there is no CRP in the blood serum. |
| What abnormal results mean: |
| Since the CRP is a general test, a positive CRP may indicate any of a number of things:Positive CRP results also occur during the last half of pregnancy or with the use of oral contraceptives. |
| What the risks are: |
Risks associated with venipuncture are slight:
- Excessive bleeding
- Fainting or feeling light-headed
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
- Multiple punctures to locate veins
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| Special considerations: |
| Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others. |
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Review Date: 11/17/2001
Reviewed By: Birgit Kovacs, M.D., Division of Rheumatology, University of Pennsylvania Medical Center, Philadelphia, PA. Review provided by VeriMed Healthcare Network.
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