Relationship between the articular manifestations of rheumatoid arthritis and circulating immune complexes detected by three methods and specific classes of rheumatoid factors.

Although detected in most patients with rheumatoid arthritis (RA), the relationship of the concentration of circulating immune complexes and specific classes of rheumatoid factors (RF) to the activity of the articular manifestations is uncertain. Therefore, 57 patients were evaluated in a prospective fashion. Combining all data, the concentration of IgG RF and the erythrocyte sedimentation rate (ESR) correlated most strongly with the articular index (Pc less than 10(-4], while the concentrations of IgM RF and IgA RF did not correlate. The quantity of immune complexes detected by the C1q-SP and the mRF-SP assays correlated significantly with articular manifestations (Pc less than 0.02 and less than 0.002) while those detected by the C1q-BA did not. Strong associations between the change of the articular index and both the change of ESR (r = 0.76, Pc less than 0.007) and the change of IgG RF (r = 0.72, Pc less than 0.014) were noted in those begun on remittive agents during the course of this investigation. Of the assays for immune complexes, changes of those detected by the C1q-SP correlated most closely with the articular index (r = 0.63) in this group. These observations support a potential role for the selective use of certain laboratory parameters, in addition to the ESR, in monitoring the articular activity of certain patients with RA.