Viscosity of plasma and blood in rheumatoid arthritis

Blood rheology was studied in 130 consecutive RA outpatients, 33 with and 97 without extra-articular disease (EAD), and compared with that in 88 blood donors. All rheological variables were significantly elevated in the RA patients compared with the controls. Painful joint count (PJC), morning stiffness (MS) and radiographic changes (RC) correlated significantly with plasma viscosity (PV), CRP, ESR and fibrinogen concentration (FC), but only in the group without EAD. Corrected blood viscosity (CBV) at a shear rate of 92/s correlated significantly only with MS. Multiple regression with PJC, MS and RC as dependent variables showed significant associations of PJC with PV, MS and CRP and RC with PV. Multiple regression with PV as the dependent variable showed significant associations with FC and IgG. RA patients with EAD had higher PV (P < 0.01), CBV at 92/s (P < 0.05) and ESR (P < 0.05) than the RA patients without EAD. Differences in profiles of viscosity variables between subgroups of EAD in RA patients were observed.