MRCEM Notes

Rheumatoid arthritis: antibodies

Pathology

Rheumatoid factor


Rheumatoid factor (RF) is a circulating antibody (usually IgM) which reacts with the Fc portion of the patients own IgG

RF can be detected by either
  • Rose-Waaler test: sheep red cell agglutination
  • Latex agglutination test (less specific)

RF is positive in 70-80% of patients with rheumatoid arthritis, high titre levels are associated with severe progressive disease (but NOT a marker of disease activity)

Other conditions associated with a positive RF include:
  • Sjogren's syndrome (around 100%)
  • Felty's syndrome (around 100%)
  • infective endocarditis (= 50%)
  • SLE (= 20-30%)
  • systemic sclerosis (= 30%)
  • general population (= 5%)
  • rarely: TB, HBV, EBV, leprosy


Anti-cyclic citrullinated peptide antibody

Anti-cyclic citrullinated peptide antibody may be detectable up to 10 years before the development of rheumatoid arthritis. It may therefore play a key role in the future of rheumatoid arthritis, allowing early detection of patients suitable for aggressive anti-TNF therapy. It has a sensitivity similar to rheumatoid factor (70-80%, see below) with a much higher specificity of 90-95%.

NICE recommends that patients with suspected rheumatoid arthritis who are rheumatoid factor negative should be test for anti-CCP antibodies.
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