A comparison between 2017 FAS and 2012 CKD-EPI equations: a multi-center validation study in Chinese adult population

The recent guidelines recommend using the estimated glomerular filtration rate (eGFR) to evaluate renal function. There are two reported full-age-spectrum (FAS) equations in 2017, which are based on serum cystatin C concentrations with or without accompanying serum creatinine level (FAS_Cr-Cys or FAS_Cys). We compared the performance and assessed the applicability of the new FAS equation with the 2012 CKD-EPI (CKD-EPI_Cys and CKD-EPI_Cr-Cys) equation in Chinese subjects.

A total of 1184 patients, mean aged 55.06 year who underwent ^99mTc-DTPA GFR measurements (rGFR) from four hospitals were enrolled. The bias (eGFR-rGFR), precision (interquartile range of difference [IQR]), and accuracy (the proportion of eGFR within 30% of rGFR [P30]) of eGFR and rGFR calculated by four equations were compared.

Generally, the equation based on the combination of Cys and Scr performed superior to that on the basis of Cys alone, either the CKD-EPI_Cr-Cys or the FAS_Cr-Cys. Detailedly, referred to rGFR (67.33 ml/min/1.73 m²), the CKD-EPI_Cys, CKD-EPI_Cr-Cys, FAS_Cys, and the FAS_Cr-Cys estimated GFR 56.46 ml/min/1.73 m², 62.79 ml/min/1.73 m², 56.45 ml/min/1.73 m², and 61.04 ml/min/1.73 m², gave ROC^AUC0.944, 0.954, 0.943, and 0.953, respectively. Another comparison as to bias, precision, P₃₀, and RMSE with FAS_Cr-Cys were - 2.87 ml/min/1.73 m², 19.01 ml/min/1.73 m², 74.16%, and 17.84 ml/min/1.73 m² showed that FAS_Cr-Cys performed approximately more accurate than other equations, as well as the diagnostic consistency of GFR staging. In the rGFR < 60 ml/min/1.73 m² subgroup, the FAS_Cr-Cys equation showed the best performance. In older subjects, compared with FAS_Cys, CKD-EPI_Cr-Cys, and CKD-EPI_Cys, the FAS_Cr-Cys equation had relatively less bias (- 8.09 vs. - 9.63, - 7.52, - 11.04, P < 0.05), most precise (15.18 vs. 16.32, 15.22, 16.63), and most accuracy, P₃₀ was statistically different from the other equations, and achieved a ideal value > 70%.

The performance of the FAS_Cr-Cys equation is better than that of the CKD-EPI_Cr-Cys equation in the Chinese population, particularly in the elderly. Yet, further modification of FAS equations from a large-scale study could be more suitable for the Chinese population, particularly in older people.