Prognostic Value of Isolated High Serum Cystatin C Levels Without Glomerular Filtration Rate Reduction

Objectives: Cystatin C is increasingly used as a marker of renal function as a complement to serum creatinine and glomerular filtration rate (GFR). We have assessed its efficacy as a predictor of mortality in a group of patients with increased cystatin C but GFR > 60 mL/min. Design and methods: We included 608 patients, 65.9% male, 34.6% had diabetes mellitus. The mean age was 58.5 +/- 14.5 years and a mean GFR of 64.1 +/- 33.5 mL/min. Patients were divided into 3 groups: CONTROL (normal cystatin C and GFR > 60 mL/min, age 53.3 +/- 12.8 years, GFR 96.6 +/- 22.4 mL/min,n = 193), INCREASED CYSTATIN (cystatin C >1.03 mg/l and GFR >60 mL/min, age 58.9 +/- 13,1 years, GFR 72.2 +/- 10.4 mL/min, n = 40) and CKD (chronic kidney disease, increased cystatin C and GFR < 60 mL/min, age 61.4 +/- 14.8 years, GFR 36.0 +/- 12.7 mL/min, n = 160). The relationship with overall mortality was analyzed using the KaplanMeier method. Results: Mean cystatin C was 0.75 +/- 0.13 versus 1.79 +/- 0.54 in CKD group and 1.14 +/- 0.14 mg/l, p < 0.001). In CONTROL group survival was 93.9% at 5 y, compared to 78.8% in the ERC group and 82.3% in the INCREASED CYSTATIN group (p < 0.001) Five-year survival before renal replacement therapy was also different for the ERC group (73%, p < 0.001 Log Rank) but not between the other two groups (CONTROL 99.0%, INCREASED CYSTATIN 94.3% p = 0.08). Conclusions: Increased plasmatic levels of cystatin C in patients with GFR > 60 mL/min was a predictor of increased mortality but not of progression to end-stage renal failure. These results confirm the interest of routinely measuring cystatin C. (c) 2024 The Author(s). Published by Elsevier Espania, S.L.U. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).