How reliable is ESR as a measure of disease activity in rheumatoid arthritis treated with hydroxychloroquine?

Forty-two patients with active rheumatoid arthritis treated with hydroxychloroquine sulphate (400 mg day-1) for six months have been compared with patients treated with D-penicillamine (n = 14), aurothiomalate (n = 13), sulphasalazine (n = 15) and chloroquine (n = 17) to compare the changes in articular index, plasma viscosity and ESR. Results indicate that while articular index and plasma viscosity show significant improvement for all treatments, the ESR fails to improve during hydroxychloroquine therapy.