Quantitation of rheumatoid factors (RF) of IgM, IgA and IgG isotypes by a simple and sensitive ELISA. Discrimination between false and true IgG-RF

Scand J Rheumatol Suppl. 1988;75:15-24. doi: 10.3109/03009748809096734.


An enzyme-linked immuno-sorbent assay (ELISA) for quantitation of rheumatoid factors (RF) of IgM, IgA and IgG isotypes has been established. A complex of human serum albumin (HSA) and rabbit IgG anti-HSA antibodies is used as antigen for RF. The binding of RF is detected by stepwise additions of biotinylated monoclonal antibodies specific for human IgM, IgG or IgA, alkaline phosphatase-conjugated streptavidin, and substrate. The assay is simple and applicable to routine testing of large numbers of sera. It discriminates between false and true IgG-RF by papain digestion of sera that turn out positive by the screening for IgG-RF. Of 241 randomly selected patients with rheumatoid arthritis (RA) as well as other rheumatoid and infectious diseases, 110 were Waaler-Rose-positive while 127 were IgM-RF-positive in ELISA. The correlation between the Waaler-Rose test and IgM-RF ELISA was highly significant (r = 0.82). By testing 65 of these sera (all IgM-RF positive), 25 (39%) were also true IgG-RF positive (42 (64%) in the screening). When 40 Waaler-Rose-positive RA patients were tested, 20 and 21 were also positive for IgG- and IgA-RF, respectively. Eight IgM-, one IgA- and no IgG-RF positive tests were recovered when 48 Waaler-Rose negative RA patients were studied.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Agglutination Tests
  • Antibodies / immunology
  • Antibodies, Monoclonal
  • Arthritis, Rheumatoid / blood
  • Enzyme-Linked Immunosorbent Assay / methods*
  • False Positive Reactions
  • Humans
  • Immunoglobulin A / analysis*
  • Immunoglobulin Fab Fragments / immunology
  • Immunoglobulin G / analysis*
  • Immunoglobulin G / immunology
  • Immunoglobulin Isotypes / analysis*
  • Immunoglobulin M / analysis*
  • Rheumatoid Factor / analysis*
  • Sensitivity and Specificity
  • Serum Albumin / immunology


  • Antibodies
  • Antibodies, Monoclonal
  • Immunoglobulin A
  • Immunoglobulin Fab Fragments
  • Immunoglobulin G
  • Immunoglobulin Isotypes
  • Immunoglobulin M
  • Serum Albumin
  • Rheumatoid Factor