Is the demonstration of immune complex useful in the activity assessment of chronic polyarthritis

In a prospective and controlled long-term study of 39 patients suffering from rheumatoid arthritis (RA), various blood parameters including the C1q-binding test (fluid phase) and the Rajicell test were performed. Blood samples were taken every three months during an observation period of eighteen months and compared with disease activity. According to these sequential analyses, immune complexes determined in the serum by these two tests do not always reflect disease activity expressed by addition of active joints. These results confirmed that the C1q-binding test often closely reflects disease activity. In patients with RA and extraarticular manifestations the C1q-binding test continuously showed increased concentrations of circulating immune complexes in the serum. In patients with predominant vasculitis the regular determination of circulating immune complexes is the best means of showing disease activity. This latter observation is especially true in patients with malignant RA. On the whole, the clinical significance of regularly performed assay for detection of immune complexes in RA appears questionable.