C-reactive protein (CRP) is produced by the liver. The level of CRP rises when there is inflammation throughout the body. It is one of a group of proteins called acute phase reactants that go up in response to inflammation. The levels of acute phase reactants increase in response to certain inflammatory proteins called cytokines. These proteins are produced by white blood cells during inflammation.
History
C-reactive protein (CRP) was identified in 1930 and was subsequently considered to be an “acute phase protein,” an early indicator of infectious or inflammatory conditions. CRP was so named because it was first identified as a substance in the serum of patients with acute inflammation that reacted with the antibody against the somatic capsular polysaccharide (C-polysaccharide) of pneumococcus.
How the Test is Performed
A blood sample is needed. This is most often taken from a vein. The procedure is called a venipuncture.
Why the Test is Performed
The CRP test is a general test to check for inflammation in the body. It is not a specific test. That means it can reveal that you have inflammation somewhere in your body, but it cannot pinpoint the exact location. The CRP test is often done with the ESR or sedimentation rate test which also looks for inflammation.
You may have this test to:
Check for flare-ups of inflammatory diseases such as rheumatoid arthritis, lupus, or vasculitis.
Determine if anti-inflammatory medicine is working to treat a disease or condition.
However, a low CRP level does not always mean that there is no inflammation present. Levels of CRP may not be increased in people with rheumatoid arthritis and lupus. The reason for this is unknown.
When CRP test is suggested ?
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
Joint pain and swelling
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. CRP is a more sensitive and accurate reflection of the acute phase response than the ESR (Erythrocyte Sedimentation Rate). ESR may be normal while CRP is elevated. CRP returns to normal more quickly than ESR in response to therapy.
*Normal Results
Generally, there are low levels of CRP detectable in the blood. The levels often increase slightly with age, female gender and in African Americans.
Increased serum CRP is related to inflammatory conditions , cardiovascular risk factors and may reflect the role of these risk factors in causing vascular inflammation.
What Abnormal Results Mean
A positive test means you have inflammation in the body. This may be due to a variety of conditions, *including:
Bacterial infections, such as sepsis
Connective tissue disease
Heart attack
Infection
Inflammatory bowel disease (IBD)
Lupus
Pneumococcal pneumonia
Rheumatoid arthritis
Rheumatic fever
An infection of the bone called osteomyelitis
Cancer
Tuberculosis
*This list is not all inclusive.
Note: A higher than normal CRP level also occur during the last half of pregnancy or with the use of birth control pills (oral contraceptives). There are other factors that can raise your CRP levels, these include cigarette smoking, obesity, and lack of exercise.
Prepare for the test?
Normally you don’t need any special preparations for a CRP test.
Are there any risks to the test?
There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
What is high-sensitivity CRP test?
A more sensitive CRP test, called a high-sensitivity C-reactive protein (hs-CRP) assay, is available to determine a person’s risk for heart disease.
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. An hs-CRP test measures much lower levels of CRP. It is used to check for risk of heart disease.
The American Heart Association doesn’t recommend an hs-CRP test for everyone. Rather, the test is most useful for people who have a 5 to 10 percent chance of having a heart attack within the next 10 years. This intermediate risk level is determined by the global risk assessment, which is based on lifestyle choices, family history and current health status.
The test also helps determine the risk of a second heart attack, as people with a high level of hs-CRP who had a heart attack are more likely to have another event than those with a normal level.
*Results of the hs-CRP in determining the risk for heart disease can be interpreted as follows:
You are at low risk of developing cardiovascular disease if your hs-CRP level is lower than 1.0 mg/L.
You are at average risk of developing cardiovascular disease if your levels are between 1.0 mg/L and 3.0 mg/L.
You are at high risk for cardiovascular disease if your hs-CRP level is higher than 3.0 mg/L.
* Note: Normal value ranges may vary slightly among different laboratories. Talk to your health care provider about the meaning of your specific test results.The examples above show the common measurements for results for these tests. Some laboratories use different measurements or may test different specimens.
Source : https://www.ucsfhealth.org/tests/003356.html
https://medlineplus.gov/lab-tests/c-reactive-protein-crp-test/
https://www.mayoclinic.org/tests-procedures/c-reactive-protein-test/about/pac-20385228
https://www.webmd.com/a-to-z-guides/c-reactive-protein-test#1
https://en.wikipedia.org/wiki/C-reactive_protein
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