C-Reactive Protein
At a Glance
Why Get Tested?
To identify the presence of inflammation, to determine its severity, and to monitor response to treatment. Research work suggests a more sensitive form of the test, high-sensitivity C-reactive protein (hs-CRP), can help assess your risk of heart disease or be more valuable in assessing the very young but currently this test is not widely available.
When to Get Tested?
When your doctor suspects that you might be suffering from an inflammatory disorder (as with certain types of arthritis and autoimmune disorders or inflammatory bowel disease) or to check for the possibility of infection (especially after surgery)
Sample Required?
A blood sample taken from a vein in your arm
The Test Sample
What is being tested?
C-reactive protein (CRP) is an acute phase protein, a substance made by the liver and released into the blood within a few hours after the start of an infection or inflammation. Increased levels are observed after a heart attack, in sepsis, and after a surgical procedure. It is often the first evidence of inflammation or an infection in the body. Its rise in the blood often precedes pain, fever, or other clinical indicators. The level of CRP can jump a thousand-fold in response to inflammation and can be valuable in monitoring disease activity.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in your 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.
The Test
How is it used?
CRP is useful in assessing patients with:
- Inflammatory bowel disease
- Some forms of arthritis
- Autoimmune diseases
- Pelvic inflammatory disease
- CRP is also used to monitor patients after surgery or other invasive procedures to detect the presence of an infection during the recovery period.
While CRP tests are not specific enough to diagnose a particular disease, it does serve as a general marker for infection and inflammation. CRP is a general marker of infection and inflammation, which can alert medical professionals that further testing and treatment may be necessary.
When is it requested?
Because CRP increases in severe cases of inflammation, the test is requested when acute inflammation is a risk (such as from an infection after surgery) or suspected based on patient symptoms. It is also requested to help evaluate chronic inflammatory conditions, such as rheumatoid arthritis and lupus and is often repeated to determine whether treatment is effective. This is particularly useful for inflammatory conditions since CRP levels drop as inflammation subsides.
What does the test result mean?
A high or increasing amount of CRP in your blood suggests that you have an acute infection or inflammation - most infections and inflammations result in CRP levels above 10 mg/L.
If the CRP level in your blood drops, it means that you are getting better and inflammation is being reduced.
When your results fall below 10 mg/L, you no longer have clinically active inflammation.
Is there anything else I should know?
CRP levels can be elevated in the later stages of pregnancy, with use of birth control pills or in women taking hormone replacement therapy. Higher levels of CRP have also been observed in the obese.
Another test to monitor inflammation is called the erythrocyte sedimentation rate (ESR). Both CRP and ESR are elevated in the presence of inflammation however, CRP appears and disappears sooner than changes in the ESR. CRP levels may therefore fall to normal if you have been treated successfully, such as for a flare-up of arthritis, but your ESR may remain abnormal for a while longer.
Common Questions
Ask a Laboratory Scientist
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.
