hs-CRP
At a Glance
Why Get Tested?
May be helpful in assessing risk of developing heart disease, cardiovascular disease, or other processes involving inflammation
When to Get Tested?
No current consensus exists on when to get tested; hs-CRP is most often done in conjunction with other tests that are ordered to assess risk of heart disease, such as a lipid profile (cholesterol, triglycerides, HDL-C, LDL-C).
Sample Required?
A blood sample drawn from a vein in your arm
Note: You may need to fast for 9-12 hours before the blood sample is taken if a lipid profile also is going to be done.
The Test Sample
What is being tested?
C-reactive protein (CRP) is made by the liver and secreted into the bloodstream. It can be measured with two different tests: the CRP test and the high-sensitivity CRP (hs-CRP) test, each measuring different ranges of CRP levels in the blood. The hs-CRP test can more accurately detect lower concentrations of the protein (it is more sensitive) than the standard CRP test. CRP increases with inflammation and infection as well as following a myocardial infarction (MI, heart attack), surgery, and trauma. As a result, CRP is one of several proteins that are often referred to as acute phase reactants and is used to monitor changes in inflammation associated with many infectious and autoimmune diseases.
It is now believed that inflammation plays a major role in atheroslcerosis (the narrowing of blood vessels due to build-up of cholesterol and other lipids), which is often associated with cardiovascular disease (CVD). Studies have shown that measuring CRP with the improved methodology of the highly sensitive assay can identify the risk level for CVD in apparently healthy people. For these high-risk individuals, this more sensitive test allows for measurement of lower concentrations of CRP that may be within the normal range but consistently at the higher end of the range. These normal but relatively high levels of CRP in otherwise healthy individuals have been found to be predictive of the future risk of a heart attack, stroke, sudden cardiac death, and peripheral arterial disease, even when cholesterol levels are within an acceptable range.
How is the sample collected for testing?
A blood sample is drawn by needle from a vein in the arm.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed; however, you may be asked to fast for 9-12 hours before the blood sample is taken if a lipid profile (including triglycerides) is to be done. In addition, you should be healthy at the time of the sample collection, without any recent illnesses, infections, inflammation, or other tissue injuries.
The Test
How is it used?
There are two different tests for CRP. The standard test measures a much wider range of CRP levels but is less sensitive in the lower ranges. The hs-CRP test can more accurately detect lower concentrations of the protein (it is more sensitive), which makes it more useful than the CRP test in predicting a healthy person's risk for cardiovascular disease.
hs-CRP is promoted by some as a test for determining the potential risk level for cardiovascular disease, heart attacks, and strokes. The current thinking is that hs-CRP can play a role in the evaluation process before one encounters one of these health problems. More clinical trials that involve measuring hs-CRP levels are currently underway in an effort to better understand its role in cardiovascular events and may eventually lead to guidelines on its use in screening and treatment decisions.
When is it ordered?
hs-CRP usually is ordered as one of several tests in a cardiovascular risk profile, often along with tests for cholesterol and triglycerides. Some experts say that the best way to predict risk is to combine a good marker for inflammation, like hs-CRP, along with the lipid profile.
What does the test result mean?
People with higher hs-CRP values have the highest risk of cardiovascular disease, and those with lower values have less of a risk. Specifically, individuals who have hs-CRP results in the high end of the normal range have 1.5 to 4 times the risk of having a heart attack as those with hs-CRP values at the low end of the normal range.
The American Heart Association and US Centers for Disease Control and Prevention have defined risk groups as follows:
- Low risk: less than 1.0 mg/L
- Average risk: 1.0 to 3.0 mg/L
- High risk: above 3.0 mg/L
These values are only a part of the total evaluation process for cardiovascular diseases. Additional risk factors to be considered are elevated levels of cholesterol, LDL-C, triglycerides, and glucose. In addition, smoking, having high blood pressure (hypertension), and being diabetic also increase the risk level.
Is there anything else I should know?
Taking nonsteroidal anti-inflammatory drugs ((NSAIDs like aspirin, ibuprofen, and naproxen) or statins may reduce CRP levels in blood. Both anti-inflammatory drugs and statins may help to reduce the inflammation, thus reducing CRP.
Because the hs-CRP test can serve as a marker for inflammation, it is important that any person having this test be in a healthy state in order for the results to be of any value in predicting the risk of coronary disease or heart attack. Any recent illness, tissue injury, infection, or other general inflammation will raise the amount of CRP and give a falsely elevated estimate of risk.
Women on hormone replacement therapy have been shown to have elevated hs-CRP levels, suggesting that this test may be useful in predicting future cardiovascular events.
Since the hs-CRP and CRP tests measure the same molecule, people with chronic inflammation, such as those with arthritis, should not have hs-CRP levels measured. Their CRP levels will be very high due to the arthritis—often too high to be measured or meaningful using the hs-CRP test.
Common Questions
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Related Pages
On This Site
Conditions: Cardiovascular Disease, Heart Disease, Heart Attack, Stroke
Elsewhere On The Web
Article Sources
NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.
Sources Used in Current Review
MedlinePlus Medical Encyclopedia. C-reactive protein. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003356.htm. Accessed December 2008.
The Evolving Role of High-Sensitivity C-Reactive Protein in Cardiovascular Health: An Expert Interview With Paul M. Ridker, MD. Posted 01/03/2006. Available online at http://www.medscape.com/viewarticle/519642 through http://www.medscape.com. Accessed December 2008.
Sources Used in Previous Reviews
American College of Cardiology clinical trials pages. Available online at http://www.acc.org/education/online/trials/acc2001/prince.htm through http://www.acc.org.
Santa Fe Colloquium on Preventive Cardiovascular Therapy. Available online at http://www.acc.org/education/online/sante%5Ffe/ridker.htm through http://www.acc.org.
Ridker PM, Stampfer MJ, Rifai N. Novel risk factors for atherosclerosis: a comparison of C-reactive protein, fibrinogen, homocysteine, lipoprotein(a), and standard cholesterol screening as predictors of peripheral arterial disease. JAMA 2001; 285:2481-2485. (May 16, 2001).
Ridker PM, Hennekens CH, Buring JE, and Rifai N. C-reactive protein and other markers of inflammation in the prediction of cardiovascular disease in women. NEJM 2000; 342:836-843. (March 23, 2000).
ARUP Lab fact sheet. Available online at http://www.aruplab.com/guides/clt through http://www.aruplab.com.
American Heart Association Journal Report 01/28/2003. AHA/CDC panel issues recommendations on CRP testing. Available online at http://www.americanheart.org/presenter.jhtml?identifier=3007984 through http://www.americanheart.org.
