How Is Rheumatoid Arthritis Diagnosed?

Criteria Used to Formulate the Diagnosis of Rheumatoid Arthritis

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Rheumatoid arthritis is a complicated disease. It's autoimmune. It's inflammatory. It's been called crippling and disabling. I have written about rheumatoid arthritis symptoms and rheumatoid arthritis treatments before, but let's take a look at how you ended up with this diagnosis in the first place. What does a doctor require to make the diagnosis of rheumatoid arthritis? What criteria helps to formulate the diagnosis?

A combination of findings from a patient's physical examination, medical history, laboratory tests, and imaging studies are used to formulate a diagnosis of rheumatoid arthritis. To establish a definitive diagnosis of rheumatoid arthritis, doctors look for a pattern of symptom progression characteristic of rheumatoid arthritis. But, keep in mind, no single entity determines the diagnosis.

ACR Classification Criteria for Rheumatoid Arthritis

In 1987, the American College of Rheumatology (ACR) established classification criteria for rheumatoid arthritis. In 2010, the criteria were updated to include findings in early rheumatoid arthritis. These criteria were said to not be for the purpose of diagnosis, but instead, for research and clinical trial purposes. Even so, they are often referred to as "diagnostic criteria".

The 2010 ACR/EULAR Score-Based Criteria for Rheumatoid Arthritis state that a score of 6 out of 10 or greater is consistent with a diagnosis of rheumatoid arthritis.

The joints involved, serologic testing, acute phase reactants, and the duration of symptoms are all considered and scored.

Joint Involvement

  • 1 medium to large joint (shoulders, elbows, knees, hips, ankles) = 0
  • 2-10 medium to large joints = 1
  • 1-3 small joints (hand and wrist joints), with or without large joint involvement = 2
  • 4-10 small joints, with or without large joint involvement = 3
  • more than 10 joints with at least one being a small joint = 5

Serology

  • Negative rheumatoid factor and negative anti-CCP = 0
  • Low positive rheumatoid factor or low positive anti-CCP = 2
  • High positive rheumatoid factor or high positive anti-CCP = 3

Acute Phase Reactants

Duration of Symptoms

  • Less than 6 weeks = 0
  • Greater than or equal to 6 weeks = 1

*Patients who do not achieve a score greater than 6 initially, should be re-assessed over time.

With regard to the updated ACR criteria, synovitis must be unexplainable by any other diagnosis. Also, symmetric joint disease (same joint affected on both sides) is not a major factor in the updated criteria, but it has always been considered characteristic of rheumatoid arthritis.

Imaging Evidence of Rheumatoid Arthritis

In early rheumatoid arthritis, plain x-rays may only reveal soft tissue swelling or joint effusion.

Other joint abnormalities tend to show up as rheumatoid arthritis progresses. This makes x-rays more valuable for prognosis, rather than diagnosis. In the first 6 months of disease onset, bony erosions are seen in 8-40% of rheumatoid arthritis patients. Yet, within the first two years of rheumatoid arthritis, 70% of patients will show evidence of bony erosions, according to Rheumatoid Arthritis: Early Diagnosis and Treatment.

While MRI can reveal erosions much earlier than plain x-rays, and greater detail of the joint and surrounding structures, it is not routinely used for diagnosis of rheumatoid arthritis. There is an increasing interest in the use of ultrasonography as an imaging tool to assess joint damage.

According to Kelley's Textbook of Rheumatology, "Imaging evidence of synovitis, including ultrasound or MRI, can be used to classify patients even in the absence of symptoms if patients have high titers of rheumatoid factor or anti-CCP and elevated acute phase reactants (sedrate or CRP)."

Should Treatment Wait for a Definitive Diagnosis?

Waiting for a definitive diagnosis based on strict criteria can be problematic though in deciding on a course of treatment. There is a window of opportunity for rheumatoid arthritis when treatment can positively affect disease progression, joint deformity, disability, and increased risk of mortality. To achieve the best outcome, experts say early treatment is essential—the earlier the better. Yet, early on, some patients do not meet the ACR criteria and are classified as having undifferentiated arthritis. The severity and persistence of synovitis should dictate treatment, not the name given to the condition.

The Bottom Line

Patients are sometimes misled by the tests that their doctor orders when rheumatoid arthritis is suspected. No single test result defines rheumatoid arthritis, not even a positive rheumatoid factor. Think of a single result as one piece of the puzzle.

Sources

Rheumatoid Arthritis: Early Diagnosis and Treatment. Cush, Weinblatt, and Kavanaugh. Professional Communications, Inc. Third Edition.

Kelley's Textbook of Rheumatology. Firestein et. al. Elsevier Saunders. Ninth Edition.

2010 Rheumatoid Arthritis Classification Criteria. Arthritis & Rheumatism. Vol. 62. No. 9. September 2010.
http://onlinelibrary.wiley.com/doi/10.1002/art.27584/full

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