Blood tests can help confirm a diagnosis of RA. People with the disease often have elevated levels of certain proteins, including C-reactive protein (CRP), in their blood.
In this article, we look at the link between RA and CRP. We describe what CRP levels show and how to reduce them.
What is CRP?
A CRP test involves giving a blood sample.
The liver makes CRP, a type of protein.
When the immune system signals inflammation, the body sends CRP through the bloodstream to the affected area.
High levels of CRP in the blood indicate chronic inflammation. This occurs with a wide range of health problems, such as:
How do doctors measure CRP levels?
Healthcare professionals measure CRP by analyzing blood samples. The procedure is the same as a regular blood test. A person does not need to fast beforehand.
In some cases, a doctor will request a high-sensitivity CRP (hs-CRP) test for a more accurate measurement. Usually, they do so when there is a risk of another issue, such as heart disease. A person must fast before a hs-CRP test.
Like any other test involving a needle, a CRP test can cause:
What do CRP levels mean?
A few tests can support a diagnosis of RA. One checks for the presence of rheumatoid factor. A more specific test looks for anti-cyclic citrullinated peptide, or anti-CCP, antibodies in the blood.
Testing CRP levels can help determine whether joint problems occur with inflammation.
While the results of these tests can help confirm a diagnosis, a doctor is more likely to focus on whether a person has symptoms of RA.
After diagnosis, doctors can monitor the condition by checking CRP levels. For example, these measurements can show how effectively a treatment is reducing inflammation.
Test results show how many milligrams of CRP are in a liter of blood (mg/l).
The medical community has no set normal range for CRP levels, because so many individual factors, such as age and medical history, affect these levels. Generally, a CRP measurement under 10 mg/l falls within a normal range. However, this can still indicate mild inflammation.
A higher measurement suggests more substantial inflammation, which can indicate a flare-up of RA symptoms.
Over time, RA can cause complications. These may involve other parts of the body and elevated levels of inflammation. For this reason, doctors can monitor CRP levels to assess the risk of these complications.
For example, people with RA have an increased risk of heart disease. A doctor can assess an individual's risk with a hs-CRP test, and a result above 3 mg/l indicates that the risk is high.
A wide variety of health conditions can cause inflammation, and determining why CRP levels are high usually requires further investigations.
The following factors can affect the results of a CRP test:
Reducing CRP levels
Over-the-counter and prescription medications can treat inflammation.
Prescription medications can reduce inflammation.
The other goals of RA treatment are to relieve pain, manage symptoms, and reduce or eliminate the risk of permanent joint damage.
To reduce inflammation, a person may take:
- over-the-counter or prescription nonsteroidal anti-inflammatory drugs (NSAIDs)
- disease-modifying antirheumatic drugs (DMARDs), which suppress the immune system
- biologics, which can slow down or prevent the progression of RA
People can use DMARDs along with NSAIDs.
A doctor can also inject steroid-based medication directly into a joint to decrease inflammation.
RA causes inflammation. In response, the body releases CRP into the bloodstream.
Measuring the levels of CRP in the blood can help with diagnosing RA.
While many factors influence a person's CRP levels, and there is no definitive normal range, CRP levels above 10 mg/l suggest substantial inflammation.
Taking RA medications can help reduce levels of inflammation and CRP in the blood.