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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.
