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A C-reactive protein (CRP) test is a blood test that measures the amount of a protein called C-reactive protein in your blood. C-reactive protein measures general levels of inflammation in your body.
High levels of CRP are caused by infections and many long-term diseases. But a CRP test cannot show where the inflammation is located or what is causing it. Other tests are needed to find the cause and location of the inflammation.
A C-reactive protein (CRP) test is done to:
A special type of CRP test, the high-sensitivity CRP test (hs-CRP), may be done to help find out your risk of a heart attack and stroke. The results can help you and your doctor make decisions about how to lower your risk. The connection between hs-CRP levels and the risk of heart attack and stroke are not understood completely. But high levels may mean that the lining of your arteries are inflamed. This may damage the arteries and raise your risk of a heart attack and stroke.
There is no special preparation for a C-reactive protein (CRP) test. You might be asked to not eat or drink for a few hours before the test.
Tell your doctor all of the medicines you are taking because some medicines can affect the results.
Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).
The health professional taking a sample of your blood will:
The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.
There is very little chance of a problem from having a blood sample taken from a vein.
A C-reactive protein (CRP) test is a blood test that measures the amount of a protein called C-reactive protein in your blood.
The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.
Results are usually available within 24 hours.
Less than 1.0 milligram per deciliter (mg/dL) or less than 10 milligrams per liter (mg/L)
Any condition that results in sudden or severe inflammation may increase your CRP levels.
Some medicines may decrease your CRP levels.
Many conditions can change CRP levels. Your doctor will talk with you about any abnormal results that may be related to your symptoms and past health.
High-sensitivity C-reactive protein (hs-CRP) measures very low amounts of CRP in the blood. This test may help find your risk of heart problems, especially when it is considered along with other risk factors such as cholesterol, age, blood pressure, and smoking. It may be done to find out if you have an increased chance of having a sudden heart problem, such as a heart attack or stroke. But the connection between high CRP levels and heart disease risk is not understood very well.
Less than 0.1 mg/dL or less than 1 mg/L
Less than 1.0 mg/L
1.0 to 3.0 mg/L
More than 3.0 mg/L
You may not be able to have the test or the results may not be helpful if:
C-reactive protein can be found with this test within a few hours of an inflammation response. So a higher-than-normal CRP level shows a current inflammation. The CRP level drops back to normal when the inflammation goes away.
CitationsFischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.Pearson TA, et al. (2003). Markers of inflammation and cardiovascular disease: American Heart Association and the Centers for Disease Control and Prevention scientific statement. Circulation, 107(3): 499–511.Other Works ConsultedBuckley DI, et al. (2009). C-reactive protein as a risk factor for coronary heart disease: A systematic review and meta-analysis for the U.S. Preventive Services Task Force. Annals of Internal Medicine, 151(7): 483–495.Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.Greenland P, et al. (2010). 2010 ACCF/AHA guideline for assessment of cardiovascular risk in asymptomatic adults: A report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines. Journal of the American College of Cardiology, 56(25): e50–e103.Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.Pearson TA, et al. (2003). Markers of inflammation and cardiovascular disease: American Heart Association and the Centers for Disease Control and Prevention scientific statement. Circulation, 107(3): 499–511.Stone NJ, et al. (2013). 2013 ACC/AHA guideline on the treatment of blood cholesterol to reduce atherosclerotic cardiovascular risk in adults: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. Circulation, published online November 12, 2013. DOI: 10.1161/01.cir.0000437738.63853.7a. Accessed November 18, 2013.U.S. Preventive Services Task Force (2009). Using nontraditional risk factors in coronary heart disease risk assessment. Available online: http://www.uspreventiveservicestaskforce.org/uspstf/uspscoronaryhd.htm.
Current as of: March 12, 2014
Author: Healthwise Staff
Medical Review: Rakesh K. Pai, MD, FACC - Cardiology, Electrophysiology & George Philippides, MD - Cardiology
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