Serum amyloid A protein during the treatment of rheumatoid arthritis with second-line drugs.

Serum amyloid A protein (SAA), serum C-reactive protein (CRP) and the ESR were measured in 19 patients with rheumatoid arthritis before treatment and during therapy with gold, penicillamine or sulphasalazine for a mean period of 14.8 months (range 6-23 months). All three measurements decreased significantly; however, only 7% of SAA values fell to within the normal range (18-44 mg/l), compared to 38% measurements of serum CRP (less than 10 mg/l) and 32% of the ESR (less than 25 mm/h). In 8 (42%) of the 19 patients, SAA remained high (greater than 400 mg/l) for 3 months or more whilst serum CRP was depressed below 20 mg/l; this discrepancy was not related to particular drugs. We conclude that during treatment of rheumatoid arthritis with gold, penicillamine or sulphasalazine, SAA concentrations can be high when serum CRP and ESR are suppressed. SAA may be a more sensitive index of disease activity.