Rheumatoid factors are non-specific and insensitive measures in most patients with rheumatic diseases. It may be detectable in a percentage (=5% to 10%) of otherwise healthy elderly subjects. However, a positive rheumatoid factor can be of help in the differential diagnosis of some cases of inflammatory arthritis (rheumatoid arthritis (RA) vs. psoriatic arthritis), and in determining the prognosis of patients with RA (sero-positive RA tends to have a more serious prognosis than sero-negative). Because of its lack of specificity, rheumatoid factor testing is not advocated for screening purposes in patients with locomotor symptoms. It has no value in following the course of the disease.

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