Significance of rheumatoid factor isotypes in seronegative rheumatoid arthritis

Rheumatol Int. 1990;10(1):43-6. doi: 10.1007/BF02274780.


In a cross-sectional study of 124 patients with definite or classical rheumatoid arthritis (RA) and negative agglutination assays, rheumatoid factor (RF) isotypes were measured using an ELISA technique. Elevated levels of IgA-RF were found in 55 patients (44%), IgG-RF in 99 (80%), and IgM-RF in 20 (16%). The levels of IgA- and IgM-RF correlated with each other (P less than 0.001). Elevated levels of IgM-RF were associated with a more severe disease course. Elevated levels of IgA-RF correlated with the occurrence of bone erosions. The results of this study suggest that in patients with RA and negative agglutination assays, both IgM- and IgA-RF are markers of disease severity.

Publication types

  • Comparative Study

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Arthritis, Rheumatoid / blood
  • Arthritis, Rheumatoid / immunology*
  • Arthritis, Rheumatoid / pathology
  • Bone and Bones / pathology
  • Enzyme-Linked Immunosorbent Assay
  • Female
  • Humans
  • Immunoglobulin A / analysis
  • Immunoglobulin Isotypes / analysis*
  • Immunoglobulin M / analysis
  • Latex Fixation Tests
  • Male
  • Middle Aged
  • Rheumatoid Factor / analysis
  • Rheumatoid Factor / classification*


  • Immunoglobulin A
  • Immunoglobulin Isotypes
  • Immunoglobulin M
  • Rheumatoid Factor