[Protein binding of salicylates in rheumatoid arthritis]

Protein binding of salicylates was determined in 16 control subjects and 27 patients suffering from rheumatoid arthritis. Results obtained after separation of the free and bound fractions by dialysis to equilibrium and measured by spectrofluorometry were analyzed using a new mathematical model. In correlation with the decrease in plasma albumin concentrations, a decrease was found in the protein binding of salicylates in patients with rheumatoid arthritis. This phenomenon was less marked in therapeutic zones and was related to the degree of severity of the inflammatory syndrome. The binding capacity per albumin molecule at saturation was decreased in patients suffering from advanced forms, suggesting that the changes seen were not due solely to quantitative variations in serum albumin levels. This study confirms the value of the determination of free salicylate levels in patients suffering from inflammatory rheumatic disorders.