Interpretation
High levels of rheumatoid factor (in general, above 20 IU/mL, 1:40, or over the 95th percentile; there is some variation among labs) occur in rheumatoid arthritis (present in 80%) and Sjögren's syndrome (present in 70%). The higher the level of RF the greater the probability of destructive articular disease. It is also found in Epstein-Barr virus or Parvovirus infection and in 5-10% of healthy persons, especially the elderly.
There is an association between rheumatoid factor and more persistently active synovitis, more joint damage and greater eventual disability.
Rheumatoid factor may also be elevated in: chronic hepatitis, primary biliary cirrhosis, any chronic viral infection, bacterial endocarditis, leukemia, dermatomyositis, infectious mononucleosis, systemic sclerosis, and systemic lupus erythematosus (SLE).
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