Thyroxine-binding prealbumin--an index of disease activity or nutritional status in rheumatoid arthritis?

Thyroxine-binding prealbumin (TBPA) concentrations were measured in 54 patients with rheumatoid arthritis (RA) and 50 control subjects. TBPA levels were significantly depressed in the RA patients, of whom 15 had values below the laboratory reference range. Although significant negative correlations were seen between TBPA and the erythrocyte sedimentation rate, C-reactive protein and alpha 1-antichymotrypsin measurements, TBPA levels showed little relationship to disease activity as assessed clinically. On the other hand, RA patients with reduced TBPA had an increased frequency of associated anthropometric and serum visceral protein abnormalities indicating nutritional impairment. TBPA is probably subjected to diverse stimuli in patients with RA and should not be considered to act as a 'pure' negative acute phase reactant.