Rheumatoid Arthritis: What CRP Levels Say About You
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Rheumatoid Arthritis: What CRP Levels Say About You

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  • Rheumatoid Arthritis

    Rheumatoid Arthritis

    Rheumatoid arthritis (RA) is a type of arthritis that can affect anyone at any age. However, it’s more common in women and often first appears in middle age. Like any type of arthritis, RA causes swollen, painful joints. 

    Unlike osteoarthritis, which is the result of the natural wear and tear of aging joints and a low level of inflammation, RA is the result of your immune system attacking your joints, causing a lot of inflammation. The exact reason for why this happens is still not fully understood. 

    Keep reading to learn more about inflammation as well as CRP levels and testing.

  • RA Inflammation

    RA Inflammation

    If you have RA, your joints are inflamed. Inflammation is a natural process that occurs when your immune system attacks a foreign invader.

    When working correctly, immune cells rush to an area of infection, like a cut, and go to work. This causes the area to become inflamed, red, and painful, but resolves.

    RA-induced inflammation occurs because your immune system mistakes your joints for an invader and persists.

  • C-Reactive Protein

    C-Reactive Protein

    C-reactive protein (CRP) is a protein that’s produced by your liver and can be found in your blood. CRP levels in your blood rise in response to inflammation. 

    The levels of CRP in your blood will rise when you have an infection. High CRP levels will fall when the infection is under control.

  • CRP and the Diagnosis of RA

    CRP and the Diagnosis of RA

    No single test can confirm that you have RA, but measuring levels of CRP in your blood can be part of a comprehensive diagnosis. It can also be used to follow the degree of inflammation overtime. 

    The criteria for diagnosing RA includes:

    • other lab tests, such as checking your blood for an antibody called rheumatoid factor and cyclic citrullinated peptide (CCP) antibody
    • the amount of swelling and pain in your joints
    • the duration of your symptoms
    • X-rays of your hands and feet to check for erosions or bone damage
  • The CRP Test

    The CRP Test

    To get a CRP test, all you need to do is give a sample of blood. Once your blood is drawn, it will go to a lab for testing. Your doctor will tell you the results, or you will check them online.

    There’s almost no risk associated with having blood drawn for the CRP test.

  • Normal CRP Levels

    Normal CRP Levels

    Your CRP levels should be normal if you don’t have any infections or chronic inflammatory illnesses such as RA, Crohn’s disease, or lupus.

    C-reactive protein is measured in milligrams of CRP per liter of blood (mg/L). Normal CRP levels are below 3.0 mg/dL. A standard CRP test often can’t even detect normal levels because they’re so low. 

    A high sensitivity CRP test can detect levels below 10.0 mg/dL. This kind of test is performed to determine risk for cardiovascular disease. Levels of CRP over 3.0 mg/dL are thought to put you at a higher-than-average risk for heart disease.

  • Elevated CRP Levels

    Elevated CRP Levels

    If you’re being tested for RA, your doctor will likely order a standard CRP test rather than a high-sensitivity test. Levels of CRP that can be detected with a standard test are considered elevated. If your CRP levels are elevated, it may be a sign of RA or another inflammatory disease. However, it’s not a confirmed diagnosis.

  • CRP Levels and Response to Treatment

    CRP Levels and Response to Treatment

    Once you’ve been diagnosed with RA, your doctor may order occasional CRP tests. Your CRP levels are useful in indicating how well your treatments are working. 

    For instance, if you try a new medication, your doctor may test your CRP levels a few weeks later. If your levels have dropped, the medication is probably helping. If your CRP levels rise, your doctor will know that you’re having a flare-up and they may choose to try a new treatment.

  • Problems with CRP Tests

    Problems with CRP Tests

    Measuring CRP levels isn’t a perfect method for diagnosing RA or determining the effectiveness of a treatment. This is because CRP isn’t specific to RA. Elevated levels of CRP can indicate any type of infection or inflammatory disease. 

    Some studies have shown that up to 45 percent of patients had normal CRP levels, yet were considered to have RA.