Serum cystatin C is associated with kidney function but not with cardiovascular risk factors or subclinical atherosclerosis in patients with Systemic Lupus Erythematosus

Cystatin C (CysC) is a protein considered as an excellent marker of renal function, and it has been suggested as an independent predictor of cardiovascular (CV) risk. We evaluated the association of serum CysC with renal function, CV risk factors, inflammation, and subclinical atherosclerosis in Systemic Lupus Erythematosus (SLE) patients. Sixty-one SLE female patients were selected according to estimated glomerular filtration rate (GFR) > 60 ml/min/1.73m2. Renal function parameters, SLE specific factors, CV risk factors, and inflammatory markers were assessed. Subclinical atherosclerosis was assessed by measuring the carotid-femoral pulse wave velocity (PWV) by Doppler velocimetry. Serum CysC concentration was measured using a particle-enhanced immunonephelometric assay that established 0.59–1.01 mg/l as reference values. Patients with high CysC showed significantly altered creatinine, microalbuminuria, and GFR in addition to a significant higher presence of traditional CV risk factors such as arterial hypertension (p < 0.001), metabolic syndrome (p < 0.001), hypertrigliceridemia (p < 0.001), tobacco habit (p < 0.05), and a strong association with arterial stiffness (p = 0.017). Positive correlation between CysC, homocysteine (r = 0.511; p < 0.001) and fibrinogen levels (r = 0.304; p < 0.02) were also observed. A significantly higher SLICC/ACR score was related to high CysC level (p = 0.011), together with higher endothelin-1 and lower TNF serum concentration (p < 0.005). Considering only patients without any renal impairment (microalbumin/creatinine <30 mg/g), no association between CysC level and CV risk factors, arterial stiffness, or SLE-related factors was found. Serum CysC is a good marker of renal function in SLE patients, but it is not independently associated with cardiovascular risk factor or subclinical atherosclerosis.