What Tests Are Used to Diagnose Rheumatoid Arthritis?
Medically reviewed by David Ozeri, MD
Rheumatoid arthritis (RA) is a chronic, autoimmune disease in which the body's own immune system attacks itself. Most commonly, RA affects the lining of the joints, but as a systemic illness, it can also affect the skin, heart, lungs, and other organs. Diagnosing RA is essential to prompt and proper treatment, which leads to better outcomes.
This article reviews the various tests and methods healthcare providers use to diagnose RA.
Diagnosing Rheumatoid Arthritis
If a healthcare provider suspects RA, the two most important steps they will take include getting a thorough medical history from you and performing a physical examination. Those two elements are crucial for arriving at a proper diagnosis.
In addition to a history and exam, blood tests and imaging studies can help give providers a better picture of a person's disease course.
Physical Examination
During a physical examination to determine whether a person has RA, a healthcare provider will examine the joints of the body closely, especially the smaller joints of the hands, wrists, and feet.
The joint swelling associated with RA is usually accompanied by warmth and other noticeable symptoms. When an inflamed joint is swollen, it tends to feel more "squishy" than bony. This is a helpful distinction between RA and osteoarthritis, in which swollen joints tend to be less inflammatory and more bony and hard.
Another typical exam finding of a person with RA is the presence of symmetrical joint swelling and tenderness. For example, if the middle knuckle or proximal interphalangeal (PIP) joint of the left hand is swollen and tender, the same joint of the right hand commonly will be affected as well. Symmetrical joint involvement also helps to make the distinction between RA and osteoarthritis.
A sign healthcare professionals used to look for in diagnosing RA is ulnar deviation of the fingers. This occurs when chronic inflammation of the metacarpophalangeal (MCP) joints, where the fingers meet the hands, leads to drifting of the fingers toward the pinky side of the hand, or the ulna bone of the forearm. This sign is not as commonly seen today thanks in large part to more accurate and prompt diagnosis and treatment of RA.
Some people also develop rheumatoid nodules.
Blood Tests
Two of the diagnostic criteria used for identifying RA are the presence or absence of autoantibodies and elevated or normal acute phase reactants, also referred to as inflammatory markers. These can be determined through blood tests.
Since RA is an autoimmune disease, the body's immune system will form antibodies against itself. Two such antibodies found in people with rheumatoid arthritis are rheumatoid factor (RF) and anti-cyclic citrullinated peptide (anti-CCP) antibodies.
Rheumatoid factor is a specific antibody formed against the body's immune system components, particularly against immunoglobulins. While not every person with RA will test positive for rheumatoid factor, an estimated 70% will.
Understanding Rheumatoid Factor
It's believed that high levels of RF indicates more aggressive disease. However, it is important to note that on its own, the presence or lack of RF is not enough to make or exclude the diagnosis of RA. RF is not particularly specific to RA, as it can also be found positive in other conditions, such as lupus, Sjögren's syndrome, and interstitial fibrosis, to name a few. Therefore, additional testing is necessary.
Unlike rheumatoid factor, the anti-cyclic citrullinated peptide antibody is more specific to RA. This means it is found almost exclusively in people with RA as opposed to other conditions. Smoking can cause a false positive low titer of anti-CCP.
The presence of anti-CCP antibodies may be detected years before symptoms begin and has been correlated to more aggressive disease. That being said, anti-CCP antibodies do not match up with disease activity and, therefore, do not necessarily need to be rechecked if initially positive.
Serologic Testing for RA
RF and/or anti-CCP antibodies may be positive in people with RA, leading to what's referred to as "seropositive RA." However, approximately 20% of people with RA will not have either a positive RF or CCP antibody, thus having "seronegative RA." Seropositive RA is associated with more aggressive disease.
Finally, since RA is a systemic inflammatory condition, it is only natural that inflammatory markers such as the erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), may be elevated at various times throughout the disease. Elevation in either the ESR or CRP is included in the 2010 EULAR/ACR (European League Against Rheumatism/American College of Rheumatology) diagnostic criteria for RA and can be used to monitor and gauge disease activity.
Some people with chronic inflammation also develop blood cell count abnormalities, such as elevated white blood cell count, elevated platelet count, and/or anemia (a low number of healthy red blood cells).
Once adequate and appropriate management is achieved, these markers should return to normal.
Imaging Studies
While imaging studies do not have a place in the current diagnostic criteria, some forms of imaging are beneficial in evaluating joints at baseline (starting point). They also can be repeated throughout the course of the disease to detect the extent of disease progression, or even the effectiveness of certain treatments.
Examples of imaging studies that may be useful include:
X-ray imaging: X-ray imaging has long been the gold standard for evaluating joints affected by RA. X-rays are able to identify late-stage erosions (occurring within three months of diagnosis), structural abnormalities, and joint deformities. It can also identify periarticular osteopenia (bone thinning around joints), which can be seen earlier in the disease process. While X-rays are still useful, advancements in technology have led to more sensitive imaging types.
Ultrasonography: Ultrasonography is a noninvasive imaging option using high-frequency sound waves (ultrasound) to provide useful information regarding the extent of inflammation present. Ultrasound imaging of affected joints can distinguish the difference between soft tissue swelling and actual inflammation. Ultrasound imaging can also show the amount of inflammation affecting a particular joint. Ultrasounds can also detect early signs of joint erosion, something dated X-rays cannot.
Magnetic resonance imaging (MRI): MRI can also be used in assessing RA. While not commonly performed for diagnostic purposes, MRIs are useful in assessing soft tissue structure, cartilage, and bones. MRIs are highly sensitive and some studies have found that they are able to detect early joint damage almost three years before conventional X-ray imaging.
Early Symptoms
RA is a complex, autoimmune disease that causes inflammation of the joints, heart, lungs, skin, and more. It's important to note that people with RA may develop and experience very different symptoms and disease course.
Some early signs and symptoms of RA include but are not limited to:
Low-grade fevers
Joint pain
Joint stiffness and swelling
Numbness or tingling of the hands
Working with a rheumatologist will ensure that RA is managed and treated effectively, leading to symptom relief and delayed progression of the disease.
Risk Factors for Developing RA
Factors that increase a person's risk of developing RA include:
Female sex
People age 60 and older
Strong family history of RA or other autoimmune diseases
Smoking
When to See a Healthcare Provider
Anyone experiencing symptoms of joint swelling, pain or tenderness, particularly worse in the morning, and/or fatigue for several weeks, should be evaluated by a healthcare provider.
A rheumatologist is a specialist who diagnoses and treats RA and other autoimmune illnesses. While primarily targeting the joints, RA can lead to inflammation elsewhere in the body, including of the heart or lungs, so untreated disease can lead to serious complications and long-term disability.
What Happens if RA Is Left Untreated?
RA is a systemic inflammatory disease, which can affect various organs throughout the body. That is why timely and effective treatment is crucial for better long-term outcomes. If an RA diagnosis is missed or if RA is left untreated, chronic inflammation can lead to long-term disability and organ damage.
Summary
RA is a systemic, autoimmune illness that primarily affects the joints and surrounding tissues. Proper diagnosis of RA can be made by a healthcare provider known as a rheumatologist.
RA can be properly diagnosed from a thorough history and physical examination, coupled with laboratory blood testing and imaging studies. Prompt and proper diagnosis of RA is critical, as any delay in disease management can lead to irreversible joint destruction and possibly permanent disability.
A Word From Verywell
If you have been experiencing fatigue, general malaise, and joint symptoms for several weeks, it may be time to speak with your healthcare provider. RA is a complex disease, but through examination and testing, your provider can diagnose the disease and develop an appropriate treatment plan.
Frequently Asked Questions
What are the diagnostic criteria for rheumatoid arthritis?
The EULAR/ACR diagnostic scoring system gives points depending on:
Number of small/large joints affected
Presence of inflammatory markers
Presence of specific antibodies
Duration of symptoms
If a person achieves a score greater than or equal to 6 out of 10, the diagnosis of RA can be made.
What are the early warning signs for rheumatoid arthritis?
Fatigue, joint swelling, joint pain and tenderness, decreased range of motion of the joints, particularly if lasting for greater than six weeks, may be indicative of RA. Anyone experiencing such symptoms should see a healthcare provider.
How many tests are needed to diagnose rheumatoid arthritis?
Blood tests play a big role in diagnosing RA. Inflammatory markers, like the ESR and CRP, along with specific antibodies, such as rheumatoid factor (RF) and anti-CCP antibodies, can help a healthcare provider rule in or out RA.
Read the original article on Verywell Health.
