How is Rheumatoid Arthritis Diagnosed?

Rheumatoid Arthritis is an autoimmune condition that affects your joints. Blood and imaging tests can help you get a proper diagnosis for RA.

Person getting a physical exam from doctor for rheumatoid arthritis

Adam Gault, SPL / Getty Images

Rheumatoid arthritis (RA) is an inflammatory autoimmune disease that primarily affects your joints. RA is characterized by an overactive immune system response which causes your body to attack its own healthy tissue by mistake. The exact cause of RA is unknown at this time.

RA can be tricky to diagnose because symptoms can mimic other types of arthritis and inflammatory diseases. If you suspect you have symptoms or may be at risk for developing RA, make an appointment with your healthcare provider. 

To get an official diagnosis, your provider will use a combination of tests, which generally include a physical exam, blood tests, and imaging tests. Getting a diagnosis and starting treatment early can slow disease progression and prevent serious joint damage.

Medical History and Physical Exam 

Your primary healthcare provider or a rheumatologist—a doctor who specializes in the joints and bones—can diagnose you with RA. During your appointment, your provider will ask about your medical history and perform a physical exam. Before your visit, try to keep a track of the severity of your symptoms and how long you have been experiencing them. This information can give your provider more information to help them make a diagnosis.

To get a better understanding of your symptoms and overall health, your provider may ask you:

  • What symptoms do you have and when did they start?
  • Where are you experiencing pain?
  • How severe is the pain?
  • Is the pain affecting your daily life?
  • Have you had any recent injuries or illnesses?
  • Does anyone in your family have a history of arthritis?

Factors such as long-term tobacco use, obesity, and stressful life events can also increase your risk of developing RA. It is common for your provider to ask you questions about your lifestyle and daily routine. 

During your physical exam, your provider may:

  • Measure your vitals (e.g., temperature, blood pressure, and heart rate)
  • Take a look at your joints, such as the wrists, elbows, knees, and ankles
  • Ask you to walk around or bend your joints to check how well they are moving 
  • Examine your joints for fluid, swelling, pressure, and visual deformities (such as areas that stick out, aren’t aligned properly, or have unusual curves)

While a medical history questionnaire and a physical exam are not enough to diagnose you with RA, these tests can help your healthcare provider figure out if they should order additional tests or refer you to a specialist. In some cases, your provider may think it is unlikely that you have RA and can then work with you to figure out other possible causes of your symptoms. 

Blood Tests

The next step of the diagnosis process is to get your blood tested. Your healthcare provider will typically order one or more blood tests to look for inflammatory markers (signs of inflammation), antibodies, and proteins that can indicate RA.

Generally, blood testing is a simple procedure that can be completed during a single appointment. Multiple blood tests can also be performed using the same sample of blood.

The four most common blood tests for RA examine:

  • Erythrocyte sedimentation rate (ESR): This looks at your red blood cells to measure inflammation in your body. 
  • C-reactive protein (CRP): This measures inflammation by checking how much CRP is being produced in your liver Your liver lets excess CRP into your blood when your body is experiencing inflammation.
  • Rheumatoid factor (RF): This checks the amount of rheumatoid factor or the antibodies that attack healthy joint tissue, in your immune system. 
  • Anti-CCP antibody: This estimates the number of cyclic citrullinated peptide (CCP) antibodies in your blood, another type of antibody that attacks healthy cells in the joints.

No one blood test can give you an official diagnosis for RA. Sometimes, your antibody levels can be high for reasons such as viral and bacterial infections. It is also possible to experience a false positive test. 

Typically, your healthcare provider will use a combination of these tests to reach a diagnosis. Positive test results in both the RF and anti-CCP tests can reliably indicate that you have RA. 

Imaging Tests

During your testing process, your healthcare provider may order imaging tests such as X-rays, MRIs, and ultrasounds. Depending on the type of test that is used, images can detect bone erosion (how worn down your bones are), inflammation, and excess fluid around the joints.

If you are in the early stages of RA, there may be little to no joint or bone erosion. In this case, your imaging tests may not have any signs of damage. This is why imaging tests are not used on their own but are combined with blood tests and physical exams to diagnose RA. 

Common imaging tests for RA can include:

  • X-ray: Radiographic imaging can identify places where the bone has been eroded between joints, but if your disease stage is early, an X-ray is unlikely to detect any bone changes. However, X-rays can give your provider a good baseline of your condition, which can be used later on to compare how the disease is progressing or if treatment is working.
  • Magnetic resonance imaging (MRI): This test uses magnets and radio waves to create a 3D image of your joints. The technology can help your provider identify signs of bone erosion, tissue inflammation, and changes to surrounding joint tissue. Generally, MRIs can show reliable joint changes, even in the early stages of RA. 
  • Ultrasound: Ultrasounds can detect similar levels of disease as MRIs, except within deep tissue. Ultrasounds are often a cheaper and more accessible test; they can often be done right in your provider's office.

During an imaging test, you will be required to keep your body still so the technician can take clear and proper photos of your joints. Test results are generally available within 24 hours. 

Diagnostic Criteria

After testing is completed, your healthcare provider will use a set of criteria developed by the American College of Rheumatology (ACR) and the European League Against Rheumatism (EULAR). The 2010 ACR-EULAR is the standard diagnostic criteria for RA. A 2020 study in Clinical Medicine deemed that these criteria are still accurate and should be used as a scoring measure to diagnose RA.

There are four categories in the ACR-EULAR criteria. Each category has a scoring guideline. A total score of six or more points indicates an RA diagnosis.

Joint Involvement
 Classification Points
1 large joint 0
2 - 10 large joints
1 - 3 small joints 
4 - 10 small joints  3
10 or more small and/or large joints
This criterion checks for how many joints are affected and whether the joints are large or small. "Large joints" refer to shoulders, elbows, hips, knees, and ankles. "Small joints" refer to the knuckles, fingers, toes, and wrists.
Serology
Classification  Points
Negative RF and negative CCP test results 0
Low-positive RF or low-positive CCP test results 2
High-positive RF or high-positive CCP test results
Another word for blood tests, the serology score refers to your rheumatoid factor (RF) and anti-CCP antibody (CCP) tests.
Acute Phase Reactants
Classification Points
Normal CRP and normal ESR test results
Abnormal CRP or abnormal ESR test results
An additional criterion for blood tests, the score for acute phase reactants is based on your C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) test results.
Duration of Symptoms
Classification Points 
Have had symptoms for less than 6 weeks 
Have had symptoms for more than 6 weeks  1
Your score for this criterion will be based on how long you have been experiencing symptoms.

If your provider tallies up a score of 6 or more at the end of this evaluation, they may make a diagnosis of RA, as long as other similar conditions (such as psoriatic arthritis and viral polyarthritis) have been ruled out.

A Quick Review

Getting an early diagnosis of RA can slow or stop disease progression and improve long-term treatment outcomes. But, diagnosing RA can be tricky since RA symptoms can mimic the symptoms of other conditions. Your provider will use a combination of physical exams, blood tests, and imaging to rule out any other conditions and give you an official RA diagnosis.  

If you think you have RA symptoms or might be at risk for developing RA, don’t hesitate to reach out to your healthcare provider for an evaluation. A quick medical history and physical exam can point your provider in the right direction and help them either rule out RA or figure out the next steps for diagnosis. 

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Sources
Health.com uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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