A comparison of cystatin C concentrations between patients with chronic interstitial nephritis and glomerular diseases.

AIMS: Cystatin C have shown to be a renal function parameter with higher sensitivity and specificity than serum creatinine. In tubular diseases, cystatin C degradation and an increase in its urinary elimination would be observed. We have tried to define if different kinds of kidney diseases may significantly affect the serum levels of cystatin C.

DESIGN AND METHODS: Four hundred and four patients were studied: 249 men and 155 women, mean age was 64.3±10.1 years. Patients were classified into three groups: (1) Chronic interstitial nephropathy (CIN), (2) Glomerular nephropathy (GN), and (3) Non- CKD patients (control). GFR was estimated though the CKD-EPI equation and the Hoek formula.

RESULTS: Median of serum creatinine levels was higher in CIN group than in GN and control groups. Median cystatin C levels were lower in control group compared with CIN and GN groups. No significant differences were found between CIN group and GN group. Nevertheless, the cystatin/creatinine rate was lower in the CIN group patients (0.94, 0.81-1.11) than in the GN group (1.02,I 0.85-1.25) as well as the control group (1.02, I 0.88-1.20). The cystatin C-estimated GFR/creatinine-estimated GFR rate was higher in the CIN group (1.18, 1.03-1.36) than in the GN patients (1.03, 0.88-1.21) and control ones (1.07, 0.88-1.20).

CONCLUSIONS: Patients with CIN had lower serum levels of cystatin C defined as cystatin C/creatinine rate when they were compared with GN subject and control ones. In the same way, the index between cystatin C-estimated GFR and creatinine-estimated GFR was higher in CIN patients.