How Rheumatoid Arthritis Is Diagnosed

How the Disease and Disease Remission Are Confirmed

rheumatoid arthritis diagnosis
© Verywell, 2018 

Rheumatoid arthritis differs from osteoarthritis ("wear-and-tear" arthritis) in that it is an autoimmune disorder in which the immune system mistakenly attacks its own cells and tissues, primarily those of the joints. As such, the disease cannot be diagnosed by symptoms alone. Instead, a physical exam and a combination of tests—including imaging and blood tests—must be used to determine whether the results meet the clinical definition of the disease.

Doing so not only ensures that the diagnosis is correct, it helps determine the appropriate course of treatment.

Physical Exam

One of the first tools of diagnosis is a physical exam. The aim of the evaluation is, in part, to determine the characteristics of the joint pain and swelling to better distinguish it from other causes of joint pain, like osteoarthritis.

Among the key differences between rheumatoid arthritis and osteoarthritis, which will direct some of the questions your physician asks you during your exam:

 Rheumatoid ArthritisOsteoarthritis
Areas AffectedTends to affect multiple joints (polyarthritis)Usually affects the hands, feet, knees, and spine; sometimes involves just a single joint (monoarthritis)
SymmetrySymmetrical, meaning that joint symptoms on one side of the body will often be mirrored on the other side of the bodyCan be either asymmetrical (unilateral) or symmetrical, particularly if many joints are involved
Fatigue, Malaise, Fever Common due to systemic (whole-body) inflammation

Not typically associated with this disease, as it is not inflammatory

Morning StiffnessLasts more than 30 minutes, sometimes more than an hour, but improves with activity

Brief; less than 15 minutes

In addition to evaluating your physical symptoms, the doctor will review your family history. Rheumatoid arthritis can often run in families, doubling your risk of the disease if a second-degree relative has it and tripling your risk if an immediate family member is affected.

Labs and Tests

Lab tests are used for two primary purposes in diagnosing rheumatoid arthritis: to classify your serostatus and to measure/monitor the level of inflammation in your body.

Serostatus

Serostatus (loosely translated as "blood status") refers to the key identifiers of the disease in your blood. If these compounds are detected in a blood test, you are said to be seropositive. If they are not found, you are deemed seronegative. Seropositive results can be classified as either low positive, moderate positive, or high/strong positive.

There are two tests used to establish your serostatus:

  • Rheumatoid factor (RF) is a type of autoantibody found in 80 percent of people living with the disease. Autoantibodies are proteins produced by the body that attack healthy cells or cell products. While high levels of RF are strongly suggestive of rheumatoid arthritis, they can occur with other autoimmune diseases such as lupus, or non-autoimmune disorders such as cancer and chronic infections.
  • Anti-cyclic citrullinated peptide (anti-CCP) is another type of autoantibody found in the majority of people with rheumatoid arthritis. Unlike RF, a positive anti-CCP test result occurs almost exclusively in people with rheumatoid arthritis. A positive result might even identify family members who are at risk for getting the disease.

Where both tests fall short is in their sensitivity, which is generally below 80 percent.

What this means is that the tests, while valuable in making a diagnosis, are prone to ambiguous or false-negative results. It is for this reason that they are used as part of the diagnostic process rather than as sole indicators.

Inflammatory Markers

Inflammation is a defining characteristic of rheumatoid arthritis. Testing is done to evaluate the level of inflammation by looking at key markers in the blood. These markers not only help us confirm the initial diagnosis but are used throughout the course of the disease to assess our response to treatment.

To this end, doctors will use two key measures:

  • Erythrocyte sedimentation rate (ESR) is a test that measures the rate by which red blood cells settle to the bottom of a long, upright tube, known as a Westergren tube, in an hour. If there is inflammation, the red blood cells will stick together and sink more quickly. It is a non-specific measurement of inflammation but one that can provide key insights valuable to a diagnosis.
  • C-reactive protein (CRP) is a type of protein produced by the liver in response to inflammation. While also non-specific, it is a more direct measure of the inflammatory response.

ESR and CRP can also be used to diagnose arthritis remission, the state of low disease activity where inflammation is more or less in check.

Other tests may be required if your doctor is looking to gauge disease progression (see below).

Imaging Tests

The role of imaging tests in rheumatoid arthritis is to identify the signs of joint damage, include bone and cartilage erosion and the narrowing of the joint spaces. They can also help track the progression of the disease and establish when surgery is needed.

Each test can provide different and specific insights:

  • X-rays are especially useful in identifying bone erosion and joint damage. While X-rays are considered the primary imaging tool for arthritis, they are not as helpful in the very early stages of the disease when changes in cartilage and synovial tissues are less apparent.
  • Magnetic resonance imaging (MRI) scans are able to look beyond the bone, spot changes in soft tissues, and even positively identify joint inflammation in early disease.
  • Ultrasounds are also better at spotting early joint erosion and can reveal specific areas of joint inflammation. This is a valuable feature given that inflammation can sometimes continue invisibly even though the ESR and CRP tell us that the person is in remission. In such cases, treatment is continued until such time as a true remission is achieved.

Classification Criteria

In 2010, the American College of Rheumatology (ACR) updated its longstanding classification criteria for rheumatoid arthritis. The revisions were motivated, in part, by advances in diagnostic technologies. While the classifications are intended for clinical research purposes, they are nevertheless used in clinical practice to provide a greater degree of diagnostic certainty.

The 2010 ACR/EULAR Classification Criteria looks at four different clinical measures and rates them on a scale of 0 to 5. A cumulative score of 6 to 10 can provide a high degree of confidence that you, in fact, have rheumatoid arthritis.

While doctors are the only ones who use this criteria, reviewing it helps further establish why making an RA diagnosis isn't something that can necessarily be done quickly or easily.

CriteriaValuePoints
Duration of SymptomsLess than six weeks0
 More than six weeks1
Joint InvolvementOne large joint0
 Two to 10 large joints1
 One to three small joints (without the involvement of larger joints)2
 Four to 10 small joints (without the involvement of larger joints)3
 Over 10 joints (with at least one small joint)5
SerostatusRF and anti-CCP are negative0
 Low RF and low anti-CCP2
 High RF and high anti-CCP3
Inflammatory MarkersNormal ESR and CRP0
 Abnormal ESR and CRP1

 

Progression

The strongest indicator of progressive joint damage in rheumatoid arthritis is said to be seropositivity. That said, seronegativity does not preclude progressive joint damage. 

Rapid progression of joint damage tends to be associated with being positive for both rheumatoid factor and anti-CCP—more likely than if someone is positive for either, rather than both. Factors that point to a poor prognosis with progressive joint damage include:

  • X-ray evidence or clinical evidence of joint damage
  • Increased number of joints involved with active synovitis, tenderness, swelling, or joint effusions
  • Elevated ESR or CRP
  • Positive for anti-CCP
  • High level of medication use, including corticosteroids, used to treat inflammation in the affected joints
  • An inadequate response to medications
  • Decreased joint function as determined by the Health Assessment Questionnaire
  • Declining quality of life

Remission

Diagnosing disease remission is not as straightforward a process. It requires not only diagnostic tests but a subjective assessment of what you, as the patient, feel about your condition. Accurately diagnosing remission is important because it determines whether certain treatments can be stopped or if doing so may be premature and cause a relapse.

To this end, the ACR has established what is called the DAS28, which is comprised of four different measures. DAS is the acronym for disease activity score, while 28 refers to the number of joints that are examined in the assessment.

The DAS looks at the following:

  • The number of tender joints your doctor finds (out of 28)
  • The number of swollen joints your doctor finds (out of 28)
  • Your ESR and CRP results (normal versus abnormal)
  • Your rating of how you feel/your overall health as noted on a scale ranging from "very good" to "very bad"

These results are then fed into a complex mathematical formula to calculate your overall score. A DAS28 of greater than 5.1 implies active disease, less than 3.2 suggests low disease activity, and less than 2.6 is considered remission.

Differential Diagnoses

In the same way that tests can help differentiate between rheumatoid arthritis and osteoarthritis, others may be ordered to ascertain if there are other causes of your symptoms. This is especially true if your rheumatoid arthritis test results are either inconclusive, ambiguous, or negative.

These may include autoimmune disorders, connective tissue diseases, and chronic inflammatory diseases such as:

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