THE FUNCTIONAL AFFINITY OF IGM RHEUMATOID-FACTOR IS RELATED TO THE DISEASE DURATION IN PATIENTS WITH RHEUMATOID-ARTHRITIS

Objective-To determine the relevance of the functional affinity of IgM rheumatoid factor (RF) to the clinical and serological characteristic s of patients with rheumatoid arthritis. Methods-The functional affini ty of IgM RF of 57 seropositive rheumatoid arthritis patients was eval uated by an enzyme Linked immunosorbent assay based on the use of a ch aotropic agent. The inhibition index was taken as an estimate of funct ional affinity. The patient group was divided into high functional aff inity subgroup 1 (functional affinity < 0.5, n = 37) and low functiona l affinity subgroup 2 (functional affinity > 0.5, n = 20). The medical records of all patients were reviewed with a particular note of the d isease activity and the articular damage score. Results-The disease du ration was shorter (P < 0.01) in subgroup 1 patients [7.9 (SD 6.4) yea rs] than in subgroup 2 patients [13.4 (11.29) years], so that Ritchie' s, Lee's, and Steinbrocker's indices were lower in the former than in the latter (P < 0.01, 0.001, and 0.01, respectively). In contrast, ery throcyte sedimentation rates, C reactive protein concentrations, antin uclear antibody, and HLA DR4 prevalences were similar in the two subgr oups. Conclusions-Different forms of RF are present during progression of the disease.