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C-reactive protein (CRP) is a protein produced by the liver that is usually increased when there is some kind of inflammatory or infectious process happening in the body, being one of the first indicators to be altered in the blood test in these situations.
This protein is widely used to assess the possibility of a non-visible infection or inflammatory process, such as appendicitis, atherosclerosis or suspected viral and bacterial infections, for example. However, CRP can also be used to assess a person's risk of developing cardiovascular disease, as the higher the CRP, the greater the risk of this type of disease.
This exam does not point out exactly which inflammation or infection the person has, but an increase in its values indicates that the body is fighting some aggressive agent.Thus, the CRP value should always be analyzed by the doctor who ordered the test, who may order other tests and evaluate the person's he alth history, in order to arrive at the most correct diagnosis. This exam is also not the exam used for the diagnosis of COVID-19, which is known as RT-PCR. Learn more about the PCR test for COVID-19.
Normal CRP value
The normal CRP value may vary according to the laboratory in which the test was performed. In general, in relation to cardiovascular risk, the values that indicate the chance of developing heart disease are:
- Very high risk: above 10 mg/L or 1 mg/dL;
- High risk: 2.0 mg/L or 0.2 mg/dL;
- Medium risk: between 1.0 and 2.0 mg/L or 0.1 and 0.2 mg/dL;
- Low risk: less than 1.0 mg/L or 0.1 mg/dL.
In relation to acute-phase inflammation, inflammation is considered when CRP levels are equal to or greater than 10 mg/L or 1 mg/dL.
Low levels of C-reactive protein can also be observed in some situations, such as in people who have had great weight loss, physical exercise, consumption of alcoholic beverages and use of some medications, and it is important that the doctor identify the cause.
The interpretation of the result must be done by the physician, because in order to reach a diagnostic conclusion, it is important that other tests are analyzed together, thus making it possible to better identify the cause of the increase or decrease in CRP.
What is the ultra sensitive PCR test
The ultra-sensitive CRP test is requested by the doctor when he wants to assess the person's risk of having cardiovascular problems, such as a heart attack or stroke. In this case, the exam is requested when the person is he althy, without any symptoms or apparent infection.This test is more specific and can detect minute amounts of CRP in the blood.
If the person is apparently he althy and has high ultra-sensitive CRP values, it means that they are at risk of developing peripheral arterial disease, or suffering a heart attack or stroke, and therefore they should eat correctly and exercise regularly. See other 7 tips to reduce the risk of cardiovascular diseases.
What can be high CRP
High C-reactive protein appears in most inflammatory and infectious processes in the human body, and may be related to various situations such as the presence of bacteria, cardiovascular diseases, rheumatism and even rejection of an organ transplant, for example.
In some cases, CRP values can indicate the severity of inflammation or infection:
- Between 1.0 to 10.0 mg/L: usually indicate mild inflammation or mild infections such as gingivitis, flu or cold;
- Between 10.0 to 40.0 mg/L: can be a sign of more severe infections and moderate infections such as chickenpox, COVID-19 or other respiratory infection;
- More than 40 mg/L: usually indicates bacterial infection;
- More than 200 mg/L: may indicate sepsis, a serious, life-threatening condition.
The increase in this protein can also indicate chronic diseases and therefore the doctor must request other tests to try to find out what led to its increase in the bloodstream, since CRP alone is not able to determine the disease. Check out the main symptoms of inflammation.
What to do when CRP is high
After confirming the high CRP values, the physician must evaluate the results of the other tests requested, as well as evaluate the patient, taking into account the symptoms presented. Thus, once the cause is identified, treatment can be initiated in a more targeted and specific way.
When the patient has only one malaise without any other symptoms or specific risk factors, the doctor may request other tests, such as the dosage of tumor markers or computed tomography, for example, to verify the chance of increased CRP being cancer-related.
When CRP values are above 200 mg/L and the diagnosis of infection is confirmed, it is usually indicated that the person is hospitalized to receive antibiotics by vein. CRP values begin to rise at 6 hours after the onset of infection and tend to decrease when antibiotics are started. If 2 days after the use of antibiotics the CRP values do not decrease, it is important that the doctor establish another treatment strategy.