hs-CRP

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Also known as: High-sensitivity CRP; Ultra-sensitive CRP

Formal name: High-sensitivity C-reactive Protein

Related tests: Lipid Profile, Cardiac Risk Assessment, Lp-PLA2

Were you looking for the CRP test, used to evaluate general inflammation?

At a Glance

Why Get Tested?

To assess your risk of developing cardiovascular disease

When to Get Tested?

No current consensus exists on when to get tested; hs-CRP is most often ordered in conjunction with other tests that are performed 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

Test Preparation Needed?

You may be instructed to fast for 9-12 hours before the blood sample is taken if a lipid profile also is going to be done at the same time.

The Test Sample

What is being tested?

C-reactive protein (CRP) is a protein produced by the liver and released into the bloodstream. The level of CRP in the blood increases with inflammation and infection as well as following a myocardial infarction (MI, heart attack), surgery, and trauma. Thus, it is one of several proteins that are often referred to as acute phase reactants. The high-sensitivity test measures small amounts of CRP in the blood in order to help evaluate a person's risk of developing cardiovascular disease (CVD).

There are two different tests that measure CRP: the standard CRP test and the high-sensitivity CRP (hs-CRP) test. Each measures different ranges of CRP levels in the blood for different purposes. The standard test measures markedly high levels of the protein to detect diseases causing significant inflammation. The hs-CRP test can more accurately detect lower concentrations of the protein than the standard CRP test and is used to evaluate individuals for risk of CVD.

It is now believed that a persistent low level of 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 CVD. CVD causes more deaths in the U.S. each year than any other cause, according to the American Heart Association. A number of risk factors have been linked to the development of CVD, but a significant number of people who have few or no identified risk factors will also develop CVD. This fact has lead researchers to look for additional risk factors that might be either causing CVD or that could be used to determine lifestyle changes and/or treatments that could reduce a person's risk of CVD.

High-sensitivity CRP is one of a growing number of cardiac risk markers that are used to help determine a person's risk of developing CVD. Studies have shown that measuring CRP with a highly sensitive assay can identify the risk level for CVD in apparently healthy people. This more sensitive test can measure CRP concentrations that are within the higher end of the normal range. These normal but relatively high levels of CRP in otherwise healthy individuals can predict 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 instructed to fast for 9-12 hours before the blood sample is taken if a lipid profile (including triglycerides) is to be done at the same time. 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?

A high-sensitivity CRP (hs-CRP) test may be used by itself, in combination with other cardiac risk markers, or in combination with a lipoprotein-associated phospholipase A2 (Lp-PLA2) test that evaluates vascular inflammation. The hs-CRP test accurately detects low concentrations of C-reactive protein to help predict a healthy person's risk of cardiovascular disease (CVD).

High-sensitivity CRP is promoted by some as a test for determining a person's risk level for CVD, heart attacks, and strokes. The current thinking is that hs-CRP can play a role in the evaluation process before a person develops one of these health problems. Clinical trials that involve measuring hs-CRP levels are currently underway in an effort to better understand its role in cardiovascular events. These studies may eventually lead to guidelines on its use in screening and treatment decisions.

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When is it ordered?

High-sensitivity CRP usually is ordered as one of several tests in a cardiovascular risk profile, often along with tests for cholesterol and triglycerides, when a person's risk of heart disease is being evaluated. 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. When hs-CRP is evaluated, it may be repeated to confirm that a person has persistent low levels of inflammation.

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What does the test result mean?

Relatively high levels of hs-CRP in otherwise healthy individuals have been found to be predictive of an increased risk of a future heart attack, stroke, sudden cardiac death, and/or peripheral arterial disease, even when cholesterol levels are within an acceptable range.

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 at 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 U.S. 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, high blood pressure (hypertension), and diabetes also increase the risk level.

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Is there anything else I should know?

Taking nonsteroidal anti-inflammatory drugs (NSAIDs, e.g., aspirin, ibuprofen, and naproxen) or statins may reduce CRP levels in blood. Both anti-inflammatory drugs and statins may help to reduce inflammation, thus reducing CRP.

It is important that any person having this test be in a healthy state for the results to be of 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.

Since the hs-CRP and CRP tests measure the same protein, people with chronic inflammation, such as those with arthritis, should not have hs-CRP levels measured. Their CRP levels will already be very high due to the arthritis, so results of the hs-CRP test will not be meaningful.

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Common Questions

1. Is hs-CRP specific for predicting heart disease?

No. CRP is a marker of inflammation, a process that can affect a number of organ systems. Most studies to date have focused on heart disease, but new research shows that having CRP in the high normal range may also be associated with other diseases such as colon cancer, complications of diabetes, and obesity.

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2. I have had cholesterol tests but never an hs-CRP test. Why?

The traditional testing methodology for CRP has been available for a number of years; however, the hs-CRP test is fairly new, and experts still don't agree on when and how often this test should be ordered. As more clinical studies are completed, this test may be more frequently ordered.

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3. What is the difference between regular CRP and hs-CRP tests?

Both tests measure the same protein in the blood. The hs-CRP test is for apparently healthy people to determine their risk of cardiovascular disease. It measures CRP in the range from 0.5 to 10 mg/L. The CRP test is ordered to evaluate patients who have signs and symptoms of a serious bacterial infection or patients with signs and symptoms of a serious chronic inflammatory disease (such as rheumatoid arthritis). It measures CRP in the range from 10 to 1000 mg/L.

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Article Sources

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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

(© 1995-2012). Test ID: HSCRP C-Reactive Protein, High Sensitivity, Serum. Mayo Clinic Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/82047 through http://www.mayomedicallaboratories.com. Accessed May 2012.

Devaraj, S. and Lin, J. (Updated 2012 February 24). High-Sensitivity C-Reactive Protein. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/2094831-overview#showall through http://emedicine.medscape.com. Accessed May 2012.

Delgado, J. et. al. (Updated 2011 April). Cardiovascular Disease (Non-traditional Risk Markers) - Risk Markers - CVD (Non-traditional). ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/CVDRiskMarkerNontrad.html?client_ID=LTD through http://www.arupconsult.com. Accessed May 2012.

Davidson, M. (2011 May 19). hs-CRP: What Is Proven and Unproven? Medscape Today from Circulation. 2011;123:731-738 [On-line information]. Available online at http://www.medscape.com/viewarticle/742591 through http://www.medscape.com. Accessed May 2012.

Greenland P, et al. 2010 ACCF/AHA Guideline for Assessment of Cardiovascular Risk in Asymptomatic Adults: Executive Summary, A Report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines. Available online at http://circ.ahajournals.org/content/122/25/2748.full#sec-20 through http://circ.ahajournals.org. Accessed May 2012.

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.

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.