Immune complexes in juvenile rheumatoid arthritis: a comparison of four methods.

Fifty-three children with juvenile rheumatoid arthritis (JRA) were tested for immune complexes (IC) by 4 different methods, Clq solid-phase assay (ClqSPA), 2% polyethylene glycol precipitation assay (PEGPA), Raji cell assay (RCA), and the conglutinin assay (KA). Seventy-nine % of JRA patients demonstrated elevated IC levels by at least 1 method. Fifty-eight % of the JRA patients have elevated levels of IC by ClqSPA, 50% by the RCA, 37% by the KA, but 0% by the PEGPA. Seventy-four % of patients with polyarticular-onset, 88% of pauciarticular-onset, and 80% of systemic-onset JRA showed elevated levels of IC by at least 1 method. In the polyarticular-onset group, both in the rheumatoid factor (RF) positive (100%) and RF negative (64%) patients, and in the systemic-onset group (60%) the most elevated levels were demonstrated by the ClqSPA. The most elevated levels were found in the pauciarticular-onset type (69%) by the RCA. The presence of elevated levels of IC by the KA correlated with the presence of RF (p less than 0.01), hidden RF (p less than 0.05), and antinuclear antibodies (p less than 0.005). Elevated levels of IC detected by the ClqSPA correlated with the presence of RF (p less than 0.01), hidden RF (p less than 0.05), and active disease (p less than 0.01).