There’s no single test for rheumatoid arthritis (RA). To help diagnose and treat the condition, your doctor will ask about your:
- medical history
- risk factors
Your doctor will also perform a physical exam and run one or more tests.
In 2010, the American College of Rheumatology (ACR) updated the diagnostic criteria for RA. Currently, a positive diagnosis requires at least six points on a classification scale. In order to get six points, a person must have:
- symptoms affecting one or more joints (up to five points)
- positive test results on a blood test for either rheumatoid factor (RF) or anti-citrullinated protein antibody (ACPA) (up to three points)
- positive c-reactive protein or erythrocyte sedimentation tests (one point)
- symptoms lasting longer than six weeks (one point)
At least one blood test must be positive to confirm the diagnosis.
Some doctors also use a more symptom-based criteria to diagnose RA.
RA is an autoimmune disease. Several different blood tests can detect immune system changes associated with RA. Some detect antibodies that may attack the joints and other organs. Others measure inflammation or overall immune system function.
Rheumatoid Factor Test
According to the ACR, RF is an antibody found in the blood of most people with RA. Higher levels of RF correlate with more severe symptoms and faster progression. However, RF tests alone cannot be used to diagnose RA. Some people with RA test negative for RF. Other people without RA may test positive.
Anti-Citrullinated Protein Antibody Test
According to Mayo Clinic, anti-cyclic citrullinated peptide (ACPA or anti-CCP) is another antibody associated with RA. If you test positive for ACPA, there’s good chance you have rheumatoid arthritis. A positive test also indicates that RA is likely to progress more quickly.
People without RA almost never test positive for ACPA. However, many RA patients test negative for ACPA. Therefore, this test is usually used in combination with other tests.
Anti-Nuclear Antibody Test
Anti-nuclear antibody (ANA) tests are a general indicator of autoimmune disease. Many people with RA have positive ANA tests. However, a positive test does not mean you have RA. Many people have positive ANA tests with no noticeable disease.
Erythrocyte Sedimentation Rate
Also called sed rate or ESR, this test measures how quickly red blood cells separate out of the blood. The sed rate is a measure of inflammation. There is typically a direct correlation between the level of the sed rate and the degree of inflammation.
C-Reactive Protein Test
C-reactive protein is produced in the liver when there is severe inflammation or infection in the body. C-reactive protein levels change more quickly than sed rates. Therefore, this test is sometimes used to measure the effectiveness of RA medications. It can also contribute to a diagnosis of RA.
In addition to blood tests for RA, other tests can also be used to detect damage caused by the disease.
X-rays can be used to take images of joints affected by RA. These pictures can assess the level of damage to:
This can help determine the best method of treatment.
A series of X-rays can be taken over a period of weeks or months to monitor RA progression. However, X-rays are not helpful in detecting the presence of early RA because the early soft tissue inflammation does not show up on X-ray images. They can only be used to detect more advanced disease.
Magnetic Resonance Imaging (MRI)
MRIs use a powerful magnetic field to take a picture of the inside of the body. Unlike X-rays, MRIs can create images of soft tissues. Therefore, they can be used to look for inflammation of the synovium. The synovium is the membrane surrounding the joints. It’s what the immune system attacks during RA.
MRIs can detect inflammation due to RA far earlier than an X-ray. However, they are not widely used in diagnosis.