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Rheumatoid Factor

Many individuals with rheumatoid arthritis have a substance in their blood called "rheumatoid factor." 

As the diagnosis of rheumatoid arthritis is based on a number of clinical factors, only one of which is the presence of the RA factor, its' presence alone is not diagnostic of rheumatoid arthritis, but is supportive of the diagnosis:

  • Some people with RA do not have the RA factor
  • Some normal people have the RA factor
  • RA factor appears in some individuals with a variety of other illnesses, including:
    • Cancer
    • Viral infections
    • Syphilis
    • Tuberculosis
    • Lupus
    • Sjoegren's syndrome

Normal Values*

RA Factor 0-69 IU/ml
(Nonreactive)

*These are general values taken from a variety of sources. The actual normal values may vary from lab to lab and from one type of testing protocol to another.