C-Reactive Protein (CRP)
Test Overview
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C-reactive protein (CRP) is a protein produced by the liver when there is inflammation somewhere in the body. A CRP test measures the amount of C-reactive protein in the blood. Higher-than-normal levels of blood CRP may indicate inflammation. However, a CRP test cannot indicate where the inflammation is located or what is causing it. Other tests are needed to determine the cause and location of the inflammation.

A C-reactive protein test is most commonly done to monitor the activity of certain inflammatory conditions. These conditions include polymyalgia rheumatica, inflammatory bowel disease, temporal arteritis, and rheumatoid arthritis.

A CRP test may also be done to evaluate a person's risk for having an acute coronary event (such as a heart attack). However, the connection between high CRP levels and heart attack risk is not yet fully known.

A CRP test is done on a sample of blood taken from a vein.

Why It Is Done
A C-reactive protein (CRP) test may be done to:
•	Help monitor the activity of certain inflammatory conditions, including polymyalgia rheumatica, inflammatory bowel disease, temporal arteritis, rheumatoid arthritis. CRP levels decrease in these conditions after treatment with corticosteroids or immunosuppresive medications.
•	Evaluate a person's risk for having an acute coronary event such as unstable angina or a heart attack.

How to Prepare
Generally, there is no special preparation before a CRP test.

How It Is Done
The person drawing blood will wrap an elastic band around your upper arm to temporarily stop the flow of blood through the veins in your arm. This makes it easier to put the needle into a vein properly because the veins below the band get larger and do not collapse easily.

The needle site is cleaned with alcohol and the needle is inserted. More than one needle stick may be needed if the needle does not get placed correctly or if the vein cannot supply enough blood.

When the needle is properly placed in the vein, a collection tube will be attached to the needle. Blood will flow into the collection tube. Sometimes more than one tube of blood is collected.

When enough blood has been collected, the band around your arm will be removed. A gauze pad or cotton ball is placed over the puncture site as the needle is withdrawn. Pressure is applied to the puncture site for several minutes and then a small bandage is often placed over it.

How It Feels
You may feel nothing at all from the needle puncture, or you may feel a brief sting or pinch as the needle goes through the skin. Some people feel a stinging pain while the needle is in the vein. However, many people do not feel any pain (or have only minor discomfort) once the needle is positioned in the vein. The amount of pain you feel depends on the skill of the person drawing the blood, the condition of your veins, and your sensitivity to pain.

Risks
There is very little risk of complications from having blood drawn from a vein. You may develop a small bruise at the puncture site. You can reduce the risk of bruising by keeping pressure on the site for several minutes after the needle is withdrawn.

Rarely, the vein may become inflamed after the blood sample is taken. This condition is called phlebitis and is is usually treated with a warm compress applied several times daily.

Continued bleeding can be a problem for people with bleeding disorders. Aspirin, warfarin (Coumadin), and other blood-thinning medications can also make bleeding more likely. If you have bleeding or clotting problems, or if you take blood-thinning medication, tell the person before your blood is drawn.

Results

Normal
Normal values may vary from lab to lab.

C-reactive protein (CRP)

0-1.0 milligrams per deciliter (mg/dL)

Greater than normal values may mean
Elevated CRP levels can be caused by any condition that results in acute inflammation, including:
•	Heart attack
•	Cancer
•	Infection
•	Inflammatory diseases, such as inflammatory bowel disease, rheumatoid arthritis, polymyalgia rheumatica, or vasculitis (including temporal arteritis).

What Affects the Test
•	Vigorous exercise can cause mildly elevated CRP levels.
•	Women who are on hormone replacement therapy (HRT) may have increased CRP levels.
•	Elevated CRP levels may occur during pregnancy or from obesity.
•	Rough handling, contamination, or inadequate refrigeration of the blood sample can cause inaccurate test results.

What to Think About
•	Sedimentation rate (ESR) is a test that is used more frequently than CRP testing to help detect inflammation in the body. Like CRP testing, an ESR test does not indicate the cause of inflammation. ESR levels increase about a week after the start of inflammation. CRP testing can detect inflammation sooner than an ESR. For more information about the ESR test, see the medical test Sedimentation Rate.
•	Since CRP testing may help detect inflammation sooner than an ESR, a CRP test may be more helpful in detecting acute inflammation (such as from appendicitis or pelvic inflammatory disease).
•	There may be a connection between long-term inflammation in the body (especially in the circulatory system) with elevated levels of CRP and heart attack risk. High-sensitivity C-reactive protein (hs-CRP) is a test that may be used to predict heart attack risk. However, it is unclear whether hs-CRP accurately predicts the risk of heart attack. Also, if hs-CRP does accurately predict heart attack risk, the most effective treatment to correct CRP levels is not known at this time. For this reason, hs-CRP testing guidelines have not been established by medical experts.