Rheumatoid Arthritis: Antibodies

Key points

• 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,
• Sjogren's syndrome (around 100%)
• Felty's syndrome (around 100%)