SERUM IGM RHEUMATOID-FACTOR BY ENZYME-LINKED-IMMUNOSORBENT-ASSAY (ELISA) DELINEATES A SUBSET OF PATIENTS WITH DEFORMING JOINT DISEASE IN SERONEGATIVE JUVENILE RHEUMATOID-ARTHRITIS

Using human IgG as an antigen in an enzyme-linked immunosorbent assay (ELISA), we looked for the presence of IgM rheumatoid factor (RF) in t he sera of 74 children with juvenile rheumatoid arthritis (JRA). Nine children had RF detectable by both latex agglutination and ELISA. Fort y-five percent (26 of 65) of the children who were seronegative by lat ex agglutination were found to be positive for IgM RF by ELISA. The pr evalence of IgM RF was higher in patients with polyarticular onset dis ease (57.4%) than in those with pauciarticular onset (38.5%) or system ic onset (27.2%) disease. The prevalence of RF was higher in sera from patients with deforming joint disease than those without deformities (P < 0.01).