title: Which antigen to use in the detection of rheumatoid factors? Comparison of patients with rheumatoid arthritis and subjects with 'false positive' rheumatoid factor reactions.
abstract: In the search for differences between rheumatoid factors (RF) in patients with rheumatoid arthritis (RA) and in non-rheumatoid subjects, the reactivity of IgM- and IgA-class RF with rabbit IgG (rIgG) and Fc fragments of rabbit and human IgG (rFc, hFc) was studied by enzyme immunoassay. From a community-based cohort (n = 7124) representing the adult population of Finland, RA patients (n = 130), other subjects positive in the Waaler-Rose (WaRo, sensitized sheep cell agglutination) test (n = 137), and controls matched for age, sex and living area were selected for further study. In RA sera there was a good correlation between the results in the WaRo test and in the IgM-RF ELISA (rIgG, rFc and hFc). A considerable number of 'false positive' sera, though positive in the WaRo test and the rIgG-ELISA, were negative in the rFc-ELISA. Twenty-two per cent of the false positive sera reacted with either hFc or rFc, both types being equally common. IgA-RF reacted more frequently with hFc than with rFc in both the RA and the 'false positive' sera. In some sera, IgM- and IgA-RFs reacted differently with human and rabbit Fc, e.g. IgM-RF reacted only with human Fc, and IgA-RF reacted with both hFc and rFc, thus suggesting different regulation of their formation.
authors: National Public Health Institute, Helsinki, Finland.
authors: T
authors: T
authors: Tuomi
mesh_terms: D000328:Adult; D000941:Antigens / Q000276:immunology*; D001172:Arthritis, Rheumatoid / Q000276:immunology*; D005189:False Positive Reactions; D006801:Humans; D007070:Immunoglobulin A / Q000032:analysis; D007141:Immunoglobulin Fc Fragments / Q000276:immunology*; D007074:Immunoglobulin G / Q000276:immunology*; D007075:Immunoglobulin M / Q000032:analysis; D012217:Rheumatoid Factor / Q000032:analysis* / Q000145:classification / Q000276:immunology
chemical_list: D000941:Antigens; D007070:Immunoglobulin A; D007141:Immunoglobulin Fc Fragments; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D012217:Rheumatoid Factor