Value of immune-complex assays in diagnosis and management.

Two complement-dependent assays for circulating immune complexes, the C1q-binding assay and the conglutinin binding, were used to study patients with suspected immune-complex disease. Complexes were detected most frequently in multisystem disease such as infective endocarditis (69%) and systemic lupus erythematosus (60%), and less frequently in isolated nephritis (26% of membrano-proliferative nephritis). Sequential estimations in 32 patients showed that concentrations of circulating immune complexes correlated with disease activity and were useful in monitoring therapy.