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
- 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
- Viral infections
- Sjoegren's syndrome
*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.