C-reactive protein (CRP) is synthesized by the liver when there is inflammation in the body. It is measured by blood test. What is his normal rate? What does it mean when it’s high or low? Above what number?
The C reactive protein (CRP) is a biological marker. It is a protein that can be measured by means of a blood test, on the one hand, to look for inflammation or infection in the body. In other words, this protein appears when there is an inflammatory reaction. On the other hand, measuring its level in the blood makes it possible to monitor the good response to a treatment. So how does a CRP test take place? How interpret the results? What does a normal rate mean? On the contrary, what to do when the CRP is very high or low? When to worry about a raise? Our guide.
C-reactive protein is a protein released by the liver when there is acute or chronic inflammation in the body
Definition: what is C-reactive protein (CRP)?
Inflammation is an immune reaction to an infectious agent such as bacteria or a dysregulated and excessive immune response. C-reactive protein is a protein released by the liver when there is acute or chronic inflammation in the bodywhether accompanied by a bacterial or viral infection, or not. In response to aggression, it can quickly reach a very high rate. “The CRP level is all the higher as the infection or inflammation is severe. For example, in the case of a small infection, the elevation of CRP will be mild to moderate“, specifies Pr Patrick Marcellin, hepatologist at Beaujon Hospital (Paris). Its rate thus increases just before the inflammation (less than 24 hours) and drops once the inflammation is treated.
What is the normal level of C-reactive protein?
The normal CRP level should be less than 6mg/L. It may be higher in some smokers or overweight people. It can also be moderately high during pregnancy. Finally, the standards can be slightly modified according to the techniques used by each laboratory, they will however be mentioned to you on the results sheet.
This test alone cannot define the cause of the inflammation.
Indications: when to do a C-reactive protein assay?
Measuring the plasma level of C-reactive protein makes it possible to find a possible infectious or inflammatory pathology (such as rheumatoid arthritis, sepsis, abscess, colitis (inflammation of the colon), myocarditis (inflammation of the heart)…) in patients who complain of symptoms which persist and suggest inflammation (redness, swelling, pain, feeling of heat, but also fever, sleep disturbances, etc.). Nevertheless, “this test alone cannot define the cause of the inflammation. For this, the patient must have recourse to additional examinations depending on the clinical context (sampling in the urine, blood, etc.). We will say that it is rather a exploration tool. On the other hand, the CRP assay makes it possible to follow the evolution of the inflammation and to see if the treatment works effectively: if the treatment works, the CRP level is supposed to decrease“, explains Professor Marcellin. The CRP is therefore also a marker for monitoring an anti-inflammatory treatment. In the case of an infection, measuring the CRP level allows you to see if the antibiotic is effective and if the inflammation is indeed disappearing. “The CRP protein assay replaces the sedimentation rate, the test that measures the rate at which red blood cells fall through an upright blood tube to detect inflammation or infection. This test, although used for a very long time, is no longer carried out because the CRP assay is more specific, reliable and sensitive“, specifies Professor Marcellin.
During a medical consultation or in the hospital, the doctor may prescribe a C-reactive protein blood test. This is a simple and relatively common test to confirm or refute the existence of inflammation. To do this, you have to make an appointment with a medical analysis laboratory.. It is best to perform this test on an empty stomach. Remember to bring your prescription, your vital card and your health insurance card.
► After putting a tourniquet around your arm, the doctor will take a quantity of blood (usually a tube) from the bend of the elbow. Your blood will be analyzed to measure the plasma level of C-reactive protein.
► Results are usually available by mail 24 to 48 hours after the exam. If the laboratory has not already done so, it is best to send the results of the assay (even if the results seem completely normal to you when you refer to the laboratory figures) to the prescribing doctor who will decide whether or not to carry out additional analyzes or to prescribe a treatment.
“No need to imagine the worst, it is necessary to wait for additional examinations”
When to worry about an increase in CRP?
A rate higher than 6 mg/L should be monitored. A slight elevation suggests that it is a trivial, transient and harmless infection. If the rise in CRP is caused by a bacterial infection, sometimes a prescription for antibiotics can be enough to cure the infection and lower the CRP level. If the patient has a known or easily diagnosed disease, measuring the CRP several times will ensure that the level drops and therefore that the treatment is effective.
What causes high or high CRP?
An elevated CRP indicates the presence of an inflammatory reaction. Its origin can be multiple:
- A bacterial infection
- A chronic viral infection
- An autoimmune disease
- A rheumatological pathology
- A digestive disorder
- A trauma
- A myocardial infarction
“But no need to imagine the worst, it is necessary to wait for additional examinations to know the precise origin of the inflammation. Thus, it will be necessary to repeat the clinical examination (questioning, additional analyses) to look for the disease (digestive pathologies, chronic viral infections, rheumatic pathologies, etc.) responsible for these symptoms.“, wishes to reassure the specialist.
What causes low CRP?
There is no minimum threshold below which a pathology is suspected. A level below the normal value just indicates a absence of inflammatory syndrome.
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Thanks to Professor Patrick Marcellin, hepatologist at Beaujon Hospital (Paris).