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What Is the Significance of a Positive Rheumatoid Factor?

It Doesn't Always Mean You Have Rheumatoid Arthritis

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Updated June 27, 2014

Question: What Is the Significance of a Positive Rheumatoid Factor?

Diagnosing rheumatoid arthritis involves a physical examination, the patient's clinical history, and diagnostic tests. The rheumatoid factor test is among the diagnostic tests commonly ordered to help diagnose rheumatoid arthritis.

  • What is the significance of the rheumatoid factor blood test in diagnosing rheumatoid arthritis?
  • What is the significance of higher levels of rheumatoid factor?
  • How is it possible that people who are negative for rheumatoid factor can still have rheumatoid arthritis?

Answer:

Patients are often times fearful, when their doctor tells them that a rheumatoid factor (RF) was found on routine laboratory testing. Immediately, they assume that they have developed rheumatoid arthritis (RA). This is simply not the case.

The rheumatoid factor is an immunologic marker in the body, found in low titer in a number of diseases, including infectious mononucleosis and other viral diseases, chronic bacterial infections, and other acute and chronic conditions. Rheumatoid factor is also found in approximately 5 percent of healthy elderly persons. Then why worry? The concern is that when found in higher titer, it does suggest rheumatic disease.

The highest levels of rheumatoid factor are usually found in rheumatoid arthritis. Clinically, higher titers tend to correlate with more severe and sustained disease, joint deformities, rheumatoid nodules, and other extraarticular features of the disease.

The presence of this marker is not, however, needed to make the diagnosis of rheumatoid arthritis. In fact 15-25 percent of all patients with rheumatoid arthritis do not have rheumatoid factor in their serum. There is no conclusive laboratory test which confirms the diagnosis of rheumatoid arthritis.

Answer provided by the late Dr. Raymond Federman, a respected rheumatologist.

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