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Diseases > Rheumatoid Factor | Arthritis | RF

Rheumatoid Factor (RF)

The name “rheumatoid factor” is a bit misleading. That’s because some patients have the “rheumatoid factor” in their blood but don’t have rheumatoid arthritis (RA). Others don’t have the “rheumatoid factor” and actually have RA. Wow, that’s confusing!

In patients in the very early stages of rheumatoid arthritis, about half (50%) will be positive for the rheumatoid factor. The other half will be negative. Once the rheumatoid factor is positive it rarely becomes negative unless the rheumatoid test was very low in the first place. Of the patients with a negative rheumatoid factor, a few things can happen:

  1. The rheumatoid factor can become positive over time and the arthritis can persist
  2. The rheumatoid factor can stay negative and the arthritis can persist
  3. The arthritis can get better

As you can see, in patients with established rheumatoid arthritis, about 75-80% will have a positive rheumatoid factor.

It’s important to realize in early rheumatoid arthritis, having a positive rheumatoid factor is like flipping a coin. Half have it and half don’t. Just because the rheumatoid test is negative doesn’t mean you don’t have RA.

So now you know that you can have rheumatoid arthritis with or without a positive rheumatoid factor. The presence of a rheumatoid factor is not insignificant. If it is positive, it can mean a couple of things:

  1. The arthritis is likely to be persistent (it won’t just go away)
  2. The arthritis can be more severe

To make things even more confusing, there are patients who have a positive rheumatoid factor (RF) who don’t have arthritis. What does this mean?

  1. In the absence of other symptoms the risk of developing RA in the future is increased
  2. There may be another disease process resulting in the positive RF such as a chronic infection (e.g. hepatitis B/C) or another autoimmune disease (e.g Sjogren’s Syndrome).