Serum complement levels in rheumatoid arthritis. A longitudinal study of 43 cases with correlation of clinical and serological data including rheumatoid factor and thermolabile inhibitor of the F-II L.P. test.

Abstract

Previous studies of serum complement levels in rheumatoid arthritis having provided conflicting results, 43 patients with rheumatoid arthritis were studied in a longitudinal fashion both clinically and serologically. A total of 925 examinations were performed. The activity of the disease was assessed for correlation with serum complement levels and concentration of rheumatoid factor and thermolabile inhibitor of the F-n L.P. test. Serum complement levels may fluctuate significantly during active rheumatoid arthritis. Abnormal complement levels found to be predominantly raised; the significant difference between high and low values in a given case exceeding those in normal controls were the characteristic changes of active rheumatoid arthritis. There was no apparent relation between serum complement changes and severity of disease. Serum complement levels remained normal in 2 patients during permanent remission of rheumatoid arthritis. Changes in concentration of rheumatoid factor and thermolabile inhibitor of the F-n L.P. test showed no significant correlation with changes in serum complement levels.