Plasma viscosity in the monitoring of therapy in rheumatoid arthritis patients.

Plasma viscosity (PV) was compared with erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and clinical measures in the monitoring of parenteral gold therapy in a longitudinal study of 40 consecutive rheumatoid arthritis (RA) patients. Significant correlations with the combined clinical variables were only found for differences in PV and not for the other laboratory tests. PV but not ESR or CRP discriminated significantly between active and inactive disease. The sensitivity and specificity for PV above the normal range as a sign of disease activity was 89% and 73%, respectively, which was superior compared with ESR and CRP. The advantages of PV over CRP and ESR justify wider use of this test and warrant further studies of PV in the monitoring of other therapies in RA patients.