Comparison of cystatin C- and creatinine-based estimated glomerular filtration rates for predicting all-cause mortality in Japanese patients with type 2 diabetes: the Fukuoka Diabetes Registry

Background: There is little information about the predictive ability of cystatin C-based estimated glomerular filtration rates (eGFR_Cys) for all-cause mortality in Asian populations. We compared the discriminatory ability of eGFR_Cys for all-cause mortality with that of creatinine-based estimated glomerular filtration rates (eGFR_Cr) in Japanese patients with type 2 diabetes. Methods: A total of 4869 participants were classified into four categories (eGFR ≤29, 30–59, 60–89, and ≥90 ml/min/1.73 m²) by eGFR_Cr and eGFR_Cys, and followed up for a median of 3.3 years. Results: 150 deaths were identified. The multivariable-adjusted risk of all-cause mortality was significantly increased in eGFR_Cr ≤29 ml/min/1.73 m² compared with eGFR_Cr ≥90 ml/min/1.73 m² [hazard ratio (HR) 2.4 (95 % confidence interval (95 % CI) 1.2–5.0)], whereas it was significantly increased in eGFR_Cys 59 ml/min/1.73 m² or lower [30–59 ml/min/1.73 m², HR 1.9 (95 % CI 1.1–3.5); ≤29 ml/min/1.73 m², HR 5.8 (95 % CI 2.8–12.0)]. Comparing eGFR_Cys with eGFR_Cr, the proportions of participants reclassified to lower and higher eGFR stages were 6.3 and 28.8 %, respectively. The multivariable-adjusted HRs for all-cause mortality were 1.8 (95 % CI 1.1–2.9) and 0.7 (95 % CI 0.4–1.1), respectively. The C statistic of the model including eGFR_Cys and other risk factors was significantly increased compared with the model including eGFR_Cr. The net reclassification improvement and the integrated discrimination improvement were significantly positive. Conclusions: Our findings suggest that eGFR_Cys has a stronger association with all-cause mortality and is superior to eGFR_Cr for predicting all-cause mortality in Japanese patients with type 2 diabetes.