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C-Reactive Protein (CRP) Test

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What is a c-reactive protein (CRP) test?

A c-reactive protein test measures the level of c-reactive protein (CRP) in your blood. CRP is a protein made by your liver. It’s sent into your bloodstream in response to inflammation. Inflammation is your body’s way of protecting your tissues if you’ve been injured or have an infection. It can cause pain, redness, and swelling in the injured or affected area. Some autoimmune disorders and chronic diseases can also cause inflammation.

Normally, you have low levels of c-reactive protein in your blood. High levels may be sign of a serious infection or other disorder.

Other names: c-reactive protein, serum

What is it used for?

A CRP test may be used to find or monitor conditions that cause inflammation. These include:

  • Bacterial infections, such as sepsis, a severe and sometimes life-threatening condition
  • A fungal infection
  • Inflammatory bowel disease, a disorder that causes swelling and bleeding in the intestines
  • An autoimmune disorder such as lupus or rheumatoid arthritis
  • An infection of the bone called osteomyelitis

Why do I need a CRP test?

You may need this test if you have symptoms of a serious bacterial infection. Symptoms include:

  • Fever
  • Chills
  • Rapid breathing
  • Rapid heart rate
  • Nausea and vomiting

If you’ve already been diagnosed with an infection or have a chronic disease, this test may be used to monitor your treatment. CRP levels rise and fall depending on how much inflammation you have. If your CRP levels go down, it’s a sign that your treatment for inflammation is working.

What happens during a CRP test?

A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This process usually takes less than five minutes.

See also  Reticulocyte Count

Will I need to do anything to prepare for the test?

You don’t need any special preparations for a CRP test.

Are there any risks to the test?

There is very little risk of having a blood test. You may have slight pain or bruise at the spot where the needle was put in, but most symptoms go away quickly.

What do the results mean?

If your results show a high level of CRP, it probably means you have some type of inflammation in your body. A CRP test doesn’t explain the cause or location of the inflammation. So if your results are not normal, your health care provider may order more tests to figure out why you have inflammation.

A higher than normal CRP level does not necessarily mean you have a medical condition needing treatment. There are other factors that can raise your CRP levels. These include cigarette smoking, obesity, and lack of exercise.

If you have questions about your results, talk to your health care provider.

Is there anything else I need to know about a CRP test?

A CRP test is sometimes confused with a high-sensitivity-(hs) CRP test. Although they both measure CRP, they are used to diagnose different conditions. A hs-CRP test measures much lower levels of CRP. It is used to check for risk of heart disease.

References

  1. Lab Tests Online [Internet]. Washington D.C.: American Association for Clinical Chemistry; c2001–2018. C-Reactive Protein (CRP); [updated 2018 Mar 3; cited 2018 Mar 3]; [about 3 screens]. Available from: https://labtestsonline.org/tests/c-reactive-protein-crp
  2. Lab Tests Online [Internet]. Washington D.C.: American Association for Clinical Chemistry; c2001–2018. Glossary: Inflammation; [updated 2017 Jul 10; cited 2018 Mar 3]; [about 3 screens]. Available from: https://labtestsonline.org/glossary/inflammation
  3. Mayo Clinic [Internet]. Mayo Foundation for Medical Education and Research; c1998–2018. C-reactive protein test; 2017 Nov 21 [cited 2018 Mar 3]; [about 3 screens]. Available from: https://www.mayoclinic.org/tests-procedures/c-reactive-protein-test/about/pac-20385228
  4. Mayo Clinic: Mayo Medical Laboratories [Internet]. Mayo Foundation for Medical Education and Research; c1995–2018. Test ID: CRP: C-Reactive Protein, Serum: Clinical and Interpretive; [cited 2018 Mar 3]; [about 3 screens]. Available from: https://www.mayomedicallaboratories.com/test-catalog/Clinical+and+Interpretive/9731
  5. National Cancer Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; NCI Dictionary of Cancer Terms: inflammation; [cited 2018 Mar 3]; [about 3 screens]. Available from: https://www.cancer.gov/publications/dictionaries/cancer-terms/def/inflammation
  6. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Blood Tests; [cited 2018 Mar 3]; [about 3 screens]. Available from: https://www.nhlbi.nih.gov/health-topics/blood-tests
  7. Nemours Children’s Health System [Internet]. Jacksonville (FL): The Nemours Foundation; c1995–2018. Blood Test: C-Reactive Protein (CRP); [cited 2018 Mar 3]; [about 3 screens]. Available from: http://kidshealth.org/en/parents/test-crp.html?ref=search&WT.ac;=msh-p-dtop-en-search-clk
  8. Quest Diagnostics [Internet]. Quest Diagnostics; c2000–2018. Test Center: C-Reactive Protein (CRP); [cited 2018 Mar 3]; [about 3 screens]. Available from: http://www.questdiagnostics.com/testcenter/TestDetail.action?ntc=4420
  9. University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; c2018. Health Encyclopedia: C-Reactive Protein (Blood); [cited 2018 Mar 3]; [about 2 screens]. Available from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=167&contentid;=c_reactive_protein_serum
  10. UW Health [Internet]. Madison (WI): University of Wisconsin Hospitals and Clinics Authority; c2018. C-Reactive Protein (CRP): Results; [updated 2017 Oct 5; cited 2018 Mar 3]; [about 8 screens]. Available from: https://www.uwhealth.org/health/topic/medicaltest/c-reactive-protein/tu6309.html#tu6316
  11. UW Health [Internet]. Madison (WI): University of Wisconsin Hospitals and Clinics Authority; c2018. C-Reactive Protein (CRP): Test Overview; [updated 2017 Oct 5; cited 2018 Mar 3]; [about 2 screens]. Available from: https://www.uwhealth.org/health/topic/medicaltest/c-reactive-protein/tu6309.html
  12. UW Health [Internet]. Madison (WI): University of Wisconsin Hospitals and Clinics Authority; c2018. C-Reactive Protein (CRP): Why It is Done; [updated 2017 Oct 5; cited 2018 Mar 3]; [about 3 screens]. Available from: https://www.uwhealth.org/health/topic/medicaltest/c-reactive-protein/tu6309.html#tu6311
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