Efficacy of tests used to monitor rheumatoid arthritis.

The relative efficacy of clinical and laboratory tests used to monitor disease activity in rheumatoid arthritis was determined by consensus analysis in a study of 21 patients treated for 6 months. Erythrocyte sedimentation rate (ESR), which is influenced by the anaemia of chronic disease and by variation in the blood concentration of acute-phase proteins, was the most effective single test. ESR was a better guide to disease severity than measurement of plasma viscosity, serum C-reactive protein, and serum orosomucoid--tests that reflect the blood concentration of acute-phase proteins only. Clinical tests performed poorly unless combined with laboratory data in a numerical index. Consensus analysis can be used to assess the efficacy of clinical and laboratory tests and to identify redundant tests.