What Having Undifferentiated Arthritis Means

Determining the Risk of Progression to Rheumatoid Arthritis

Undifferentiated arthritis (UA) is an umbrella term for cases of arthritis that don't fit a specific diagnosis. Despite the many types of arthritis that are well-defined by the medical community, people's symptoms don't always fit neatly into a well-established category. For instance, you might be in the early stages of inflammatory arthritis but have a pattern of symptoms that's not consistent with any specific type of arthritis. Also, rheumatic diseases share a lot of the same symptoms.

A diagnosis of UA likely means that it's just too early to make a specific diagnosis but you have symptoms that need to be treated.

Outcomes of Undifferentiated Arthritis

It is estimated that between 40% and 50% of people with undifferentiated arthritis undergo spontaneous remission. That means the symptoms go away on their own.

Approximately 30% of people with this diagnosis develop rheumatoid arthritis (RA), while the remaining 20% to 30% develop other types of inflammatory arthritis.

RA is a chronic, often-debilitating disease. Early diagnosis and treatment are crucial for slowing or stopping its progression, so it is important for doctors to predict which people with undifferentiated arthritis are likely to develop RA.

Predicting the Course

In 2008, a method of predicting the course of UA was developed in Europe and published in the journal Arthritis & Rheumatism. It looked at several factors to determine your level of risk.

Factors included:

The method was found to be highly accurate in predicting who would progress from UA to RA.

In 2010, the American College of Rheumatology collaborated with the European League Against Rheumatism to revise the guidelines used to diagnose rheumatoid arthritis. The new guidelines focused on earlier stages of the disease rather than the late-stage characteristics of persistent or erosive RA that had been predominant before.

Under the revised guidelines, a definite diagnosis of RA is based on:

  • The confirmed presence of synovitis (inflammation of the joint lining) in at least one joint
  • The absence of another diagnosis that better explains the synovitis
  • Four assessments resulting in a combined total score of between six and 10 (see table)
Assessment for Diagnosing RA Score Range
Number and location of affected joints 0-5
Blood tests positive for rheumatoid factor or anti-CCP 0-3
Blood tests showing high CRP or sedimentation rate 0-1
Symptom duration 0-1

These guidelines intended to improve early diagnosis of RA, leading to fewer diagnoses of UA and earlier treatment.

Is There a Role for Imaging Studies?

Radiography techniques such as X-rays and magnetic resonance imaging (MRIs) offer a lot of information for a doctor trying to predict whether UA will progress to RA, particularly when the images show erosions of the hands and feet.

However, screening assessments are more desirable for this purpose as imaging is time-consuming and expensive.

To Treat or Not to Treat

The progression of RA is similar whether your first diagnosis was RA or UA that then progressed to RA. That raises the question of whether it's best to prescribe RA drugs for UA patients.

Some small studies have evaluated the use of disease-modifying anti-rheumatic drugs (DMARDs) or biologics to prevent UA from progressing to RA. According to a review of this research, it may be a sound strategy with certain drugs.

Results suggested that methotrexate and Orencia (abatacept) were more effective than a placebo at preventing a progression to RA, while Remicade (infliximab) was not. It will take more, larger studies to say for certain, though.

DMARDs and biologic drugs are, in fact, the preferred first-line treatments for RA. They're effective, but they do come with some serious risks and side effects.

Waiting to take these drugs until you have a definite diagnosis of RA means you won't face those risks unnecessarily if you're among those whose symptoms spontaneously go away.

On the other hand, early treatment gives you the best chance at preventing disease progression, disability, and decreased quality of life if you do go on to develop RA.

This dilemma demonstrates why it's so important to understand who's at risk.

A Word From Verywell

If you have been diagnosed with undifferentiated arthritis and are worried that it will become rheumatoid arthritis, talk to your doctor about your specific risk factors. Once you know what the likelihood is, you'll be better able to work together on the best course of treatment for protecting your health and functionality.

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