Cystatin C, Renal Function, and Atherosclerosis in Rheumatoid Arthritis

Objective.We examined the hypothesis that cystatin C, a novel marker of renal function, is elevated in rheumatoid arthritis (RA) and is associated with inflammation and coronary atherosclerosis.Methods.We measured serum cystatin C, creatinine, tumor necrosis factor-α and interleukin 6 concentrations, coronary artery calcium score (CACS), and Modified Diet in Renal Disease estimated glomerular filtration rate in 167 patients with RA and 91 controls.Results.Cystatin C was higher in RA patients [median (IQR) 1.16 (0.99–1.35) mg/l] than controls [1.01 (0.90–1.19) mg/l; p < 0.001] and correlated positively with erythrocyte sedimentation rate (p < 0.001), C-reactive protein (p = 0.01), 28-joint Disease Activity Score (p = 0.006), and Framingham risk score (FRS; p = 0.02). Cystatin C was correlated with CACS (p < 0.001) in RA, but this was not significant after adjustment for age, race, sex, and FRS (p = 0.44).Conclusion.Cystatin C concentrations are higher in RA than controls and may reflect inflammation and undetected subclinical renal dysfunction. Cystatin C provides information regarding the risk of atherosclerosis in RA, but this is not independent of the information provided by conventional cardiovascular risk factors.