title: Quantitation of rheumatoid factors (RF) of IgM, IgA and IgG isotypes by a simple and sensitive ELISA. Discrimination between false and true IgG-RF.
abstract: 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.
authors.affiliation: Institute of Immunology and Rheumatology, Rikshospitalet University Hospital, Oslo, Norway.
authors.forename: G
authors.initials: G
authors.lastname: Kleveland
authors.forename: T
authors.initials: T
authors.lastname: Egeland
authors.forename: T
authors.initials: T
authors.lastname: Lea
mesh_terms: D000372:Agglutination Tests; D000906:Antibodies / Q000276:immunology; D000911:Antibodies, Monoclonal; D001172:Arthritis, Rheumatoid / Q000097:blood; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005189:False Positive Reactions; D006801:Humans; D007070:Immunoglobulin A / Q000032:analysis*; D007140:Immunoglobulin Fab Fragments / Q000276:immunology; D007074:Immunoglobulin G / Q000032:analysis* / Q000276:immunology; D007132:Immunoglobulin Isotypes / Q000032:analysis*; D007075:Immunoglobulin M / Q000032:analysis*; D012217:Rheumatoid Factor / Q000032:analysis*; D012680:Sensitivity and Specificity; D012709:Serum Albumin / Q000276:immunology
chemical_list: D000906:Antibodies; D000911:Antibodies, Monoclonal; D007070:Immunoglobulin A; D007140:Immunoglobulin Fab Fragments; D007074:Immunoglobulin G; D007132:Immunoglobulin Isotypes; D007075:Immunoglobulin M; D012709:Serum Albumin; D012217:Rheumatoid Factor