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To identify the presence of inflammation and to monitor response to treatment for an inflammatory disorder
When your healthcare provider suspects that you have an acute condition causing inflammation, such as a serious bacterial or fungal infection or when you are suffering from an inflammatory disorder such as arthritis, an autoimmune disorder, or inflammatory bowel disease
A blood sample taken from a vein
C-reactive protein (CRP) is a protein made by the liver. CRP levels in the blood increase when there is a condition causing inflammation somewhere in the body. A CRP test measures the amount of CRP in the blood to detect inflammation due to acute conditions or to monitor the severity of disease in chronic conditions.
CRP is a non-specific indicator of inflammation and one of the most sensitive acute phase reactants. That means that it is released into the blood within a few hours after an injury, the start of an infection, or other cause of inflammation. Markedly increased levels can occur, for example, after trauma or a heart attack, with active or untreated autoimmune disorders, and with serious bacterial infections, such as in sepsis. The level of CRP can jump as much as a thousand-fold in response to bacterial infection, and its rise in the blood can precede pain, fever, or other signs and symptoms.
The CRP test is not diagnostic, but it provides information to your healthcare practitioner as to whether inflammation is present, without identifying the source of the inflammation. This information can be used in conjunction with other factors such as signs and symptoms, physical exam, and other tests to determine if you have an acute inflammatory condition or are experiencing a flare-up of a chronic inflammatory disease. Your healthcare practitioner may then follow up with further testing and treatment.
This standard CRP test is not to be confused with an hs-CRP test. These are two different tests that measure CRP and each test measures a different range of CRP level in the blood for different purposes:
The C-reactive protein (CRP) test is used to detect inflammation.
For example, CRP may be used to detect or monitor significant inflammation in acute conditions, such as:
The CRP test is useful in monitoring chronic inflammatory conditions to detect flare-ups and/or to determine if treatment is effective. Some examples include:
Examples of other uses:
CRP may sometimes be ordered along with an erythrocyte sedimentation rate (ESR), another test that detects inflammation, or procalcitonin, a test that indicates sepsis. While the CRP test is not specific enough to diagnose a particular disease, it does serve as a general marker for infection and inflammation, thus alerting healthcare practitioners that further testing and treatment may be necessary. Depending on the suspected cause, a number of other tests may be performed to identify the source of inflammation.
The CRP test may be ordered when it is suspected that you have a serious bacterial infection based on your medical history and signs and symptoms. It may be ordered, for example, when a newborn shows signs of infection or when you have symptoms of sepsis, such as:
It may also be ordered on a regular basis to monitor conditions such as rheumatoid arthritis and lupus and is often repeated at intervals to determine whether treatment is effective. This is particularly useful for inflammation problems since CRP levels drop as inflammation subsides.
It is also ordered and monitored after surgery to ensure that you are free of post-surgery infection.
The level of CRP in the blood is normally low.
Increased CRP level:
If the CRP level is initially elevated and drops, it means that the inflammation or infection is subsiding and/or responding to treatment.
"Chronic inflammatory diseases" is a general term used to describe long-lasting or frequently recurring bouts of inflammation associated with a more specific disease. Chronic inflammation can be caused by a number of different conditions such as arthritis, lupus, or inflammatory bowel disease (Crohn disease or ulcerative colitis).
Both tests are essentially the same, measuring the same substance in the blood. However, the high sensitivity CRP (hs-CRP) test measures very small amounts of CRP in the blood and is ordered most frequently for seemingly healthy people to assess their potential risk for heart problems. It typically measures CRP in the range from 0.3 to 10 mg/L. The regular CRP test is ordered for those at risk for infections or chronic inflammatory diseases (see above). It measures CRP in the range from 8 to 1000 mg/L (or 0.8 to 100 mg/dL).
Make sure to follow the instructions or recommendations of your healthcare provider. CRP levels generally drop down when infection is resolved with treatment.
It may be performed in a larger clinic, but most CRP tests will be performed in a laboratory.
CRP levels can be elevated in the later stages of pregnancy as well as with use of birth control pills or hormone replacement therapy (i.e., estrogen). Higher levels of CRP have also been observed in people who are obese. CRP can also be increased in people who have cancer.
The erythrocyte sedimentation rate (ESR) test will also be increased in the presence of inflammation; however, CRP increases sooner and then decreases more rapidly than the ESR.
Sources Used in Current Review
2019 review completed by Sami Albeiroti, PhD, DABCC, Scientific Director, Sutter Health Shared Laboratory.
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