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C-reactive protein
CRP; High-sensitivity C-reactive protein; hs-CRP
C-reactive protein (CRP) is produced by the liver. The level of CRP rises when there is inflammation throughout the body. It is one of a group of proteins called "acute phase reactants" that go up in response to inflammation.
This article discusses the blood test done to measure the amount of CRP in your blood.
How the Test is Performed
A blood sample is needed. This is most often taken from a vein. The procedure is called a venipuncture .
Venipuncture
Venipuncture is the collection of blood from a vein. It is most often done for laboratory testing.
How to Prepare for the Test
No special steps are needed to prepare 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
The CRP test is a general test to check for inflammation in the body. It is not a specific test. That means it can reveal that you have inflammation somewhere in your body, but it cannot pinpoint the exact location. The CRP test is often done with the ESR or sed rate test which also looks for inflammation.
ESR
ESR stands for erythrocyte sedimentation rate. It is commonly called a "sed rate. "It is a test that indirectly measures how much inflammation is in...
You may have this test to:
-
Check for flare-ups of inflammatory diseases such as
rheumatoid arthritis
, lupus, or vasculitis.
Rheumatoid arthritis
Rheumatoid arthritis (RA) is a long-term disease. It leads to inflammation of the joints and surrounding tissues. It can also affect other organs....
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However, a low CRP level does not always mean that there is no inflammation present. Levels of CRP may not be increased in people with rheumatoid arthritis and lupus. The reason for this is unknown.
A more sensitive CRP test, called a high-sensitivity C-reactive protein (hs-CRP) assay, is available to determine a person's risk for heart disease.
Normal Results
Normal CRP values vary from lab to lab. Generally, there is no CRP detectable in the blood.
According to the American Heart Association, results of the hs-CRP in determining the risk for heart disease can be interpreted as follows:
- You are at low risk of developing cardiovascular disease if your hs-CRP level is lower than 1.0 mg/L.
- You are at average risk of developing cardiovascular disease if your levels are between 1.0 mg/L and 3.0 mg/L.
- You are at high risk for cardiovascular disease if your hs-CRP level is higher than 3.0 mg/L.
Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
The examples above show the common measurements for results for these tests. Some laboratories use different measurements or may test different specimens.
What Abnormal Results Mean
A positive test means you have inflammation in the body. This may be due to a variety of conditions, including:
-
Cancer
Cancer
Cancer is the uncontrolled growth of abnormal cells in the body. Cancerous cells are also called malignant cells.
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-
Heart attack
Heart attack
Most heart attacks are caused by a blood clot that blocks one of the coronary arteries. The coronary arteries bring blood and oxygen to the heart. ...
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- Inflammatory bowel disease (IBD)
-
Lupus
Lupus
Systemic lupus erythematosus (SLE) is an autoimmune disease. In this disease, the body's immune system mistakenly attacks healthy tissue. It can af...
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Pneumococcal
pneumonia
Pneumonia
Pneumonia is a breathing (respiratory) condition in which there is an infection of the lung. This article covers community-acquired pneumonia (CAP). ...
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-
Rheumatic fever
Rheumatic fever
Rheumatic fever is a disease that may develop after an infection with group A streptococcus bacteria (such as strep throat or scarlet fever). It can...
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Tuberculosis
Tuberculosis
Pulmonary tuberculosis (TB) is a contagious bacterial infection that involves the lungs. It may spread to other organs.
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This list is not all inclusive.
Note: Positive CRP results also occur during the last half of pregnancy or with the use of birth control pills (oral contraceptives).
Risks
Risks associated with having blood drawn are slight but may include:
- Excessive bleeding
- Fainting or feeling light-headed
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
References
Ridker PM, Libby P, Buring JE. Risk markers and the primary prevention of cardiovascular disease. In: Mann DL, Zipes DP, Libby P, Bonow RO, Braunwald E, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine . 10th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 39.
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Blood test - illustration
Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. Preparation may vary depending on the specific test.
Blood test
illustration
-
Blood test - illustration
Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. Preparation may vary depending on the specific test.
Blood test
illustration
Review Date: 1/20/2015
Reviewed By: Gordon A. Starkebaum, MD, Professor of Medicine, Division of Rheumatology, University of Washington School of Medicine, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.
