C-reactive protein

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:
No preparation is necessary for this test

How it Feels:
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 .

Risks:
Risks associated with venipuncture are slight:
  • excessive bleeding
  • fainting or feeling lightheaded
  • hematoma (blood accumulating under the skin)
  • infection (a slight risk any time the skin is broken)
  • multiple punctures to locate veins



Why this 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 main point of importance of CRP is it's interaction with the complement system, which is one of the body's defense mechanisms against foreign bodies.

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.

Abnormal Results:
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.

Cost:
Information not available.

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.