6 Rheumatoid Arthritis Blood Tests, Plus Other Diagnostic Tools

An erythrocyte sedimentation rate (ESR) test evaluates how much inflammation is present in your body. The test measures how quickly your red blood cells, called erythrocytes, separate from your other blood cells in a lab when they are treated with a substance that prevents clotting.
Red blood cells clump together when there’s inflammation in your body, making them separate from your other blood cells much faster. Low ESR levels indicate low levels of inflammation while high ESR results indicate high levels of inflammation.
Doctors use this test to diagnose rheumatoid arthritis because this condition causes inflammation throughout your body. An ESR test on its own, however, is not enough to diagnose rheumatoid arthritis.
Inflammation and a rise in ESR levels can be caused by other chronic conditions, and by infections or injuries. However, your ESR rate can help point doctors in the right direction. For example, very elevated ESR levels would likely indicate an infection and not rheumatoid arthritis.
A C-reactive protein (CRP) test looks for the amount of CRP protein in your bloodstream. CRP is a protein produced by your liver. Your liver releases CRP when there’s an infection in your body. CRP helps start your immune system response to the infection. This leads to inflammation throughout your body.
Autoimmune conditions, such as rheumatoid arthritis, can result in high levels of CRP in your bloodstream. A CRP test measures CRP and indicates the presence of inflammation. Similar to an ESR test, a CRP test can’t confirm rheumatoid arthritis on its own. However, it can give doctors a good idea of how much inflammation is present in your body and how active your immune system is.
A full blood count, also known as a complete blood count (CBC), evaluates the cells that make up your blood. This includes your white blood cells, red blood cells, and platelets.
When you’re healthy, your body can make, release, and regulate the amount of each type of blood cell you need for body functions.
Rheumatoid arthritis doesn’t typically cause a disruption to your blood cells, but many conditions with similar symptoms do. A CBC with very abnormal results might indicate rheumatoid arthritis isn’t the right diagnosis.
Rheumatoid factors are immune system proteins that sometimes attack the healthy tissue in your body. A rheumatoid factor test measures the level of rheumatoid factor proteins in your bloodstream.
High levels of rheumatoid factors often point to rheumatoid arthritis, as well as Sjogren’s syndrome, and other autoimmune conditions. Results that show a high level can be helpful in confirming a rheumatoid arthritis diagnosis.
However, people without autoimmune conditions sometimes have a high level of rheumatoid factor proteins, and not everyone with rheumatoid arthritis has a high level of rheumatoid factor proteins.
Cyclic citrullinated peptide (CCP) antibodies are a type of immune system protein called an autoantibody. Autoantibodies are abnormal proteins that attack healthy blood cells and tissues.
Between 60 and 80 percent of people with rheumatoid arthritis have CCP antibodies in their blood. An anti-CCP antibody test — also called an ACCP test or CCP-test — looks for the presence of these antibodies to help confirm rheumatoid arthritis.
An anti-CCP test can also help doctors determine the severity of a rheumatoid arthritis case. High levels of CCP at diagnosis indicate an increased risk for the fast progression of joint damage.
Doctors typically perform both a rheumatoid factor (RF) test and an anti-CCP test when evaluating a person they suspect may have rheumatoid arthritis. A positive result for either test indicates a higher risk for RA, and that risk is increased when both tests are positive. That said, both tests are negative in up to 50 percent of people with RA, and the tests remain negative during follow-up testing in 20 percent of those with RA.
Antinuclear antibodies (ANA) are a type of autoantibody produced by your immune system. They act abnormally and attack healthy tissues and cells. The presence of ANAs can indicate an autoimmune condition.
ANA testing looks for the presence of ANAs and can help confirm a rheumatoid arthritis diagnosis.
Blood tests aren’t the only method that can be used to diagnose rheumatoid arthritis. You might also have a variety of other tests done to help confirm rheumatoid arthritis. These include:
Physical assessment. A physical assessment can help determine how much your symptoms are impacting your daily life. You might be asked how well you can do daily tasks such as showering, eating, and dressing. A physical therapist might also assess your grip, walk, and balance.
Joint scan. A joint scan looks for inflammation and damage in your joints. It can help confirm a rheumatoid arthritis diagnosis.
Imaging tests. X-rays and MRIs create detailed pictures of your bones, muscles, and joints that can help diagnose rheumatoid arthritis.
There’s no single test that can confirm rheumatoid arthritis. However, multiple blood tests can help indicate rheumatoid arthritis is the correct diagnosis.
Blood tests look for the presence of inflammation and immune system proteins that often go along with rheumatoid arthritis. The results of these tests can be used along with imaging tests and an assessment of your symptoms to diagnose rheumatoid arthritis.
Last medically reviewed on October 25, 2021
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