Figure 5. Univariate linear regression plots of BeGFR against MDRD eGFR using the four CDBs. (A–D) and MS-detected sCr (E) for all participants at Stages 0–4 after log10 transformation. Univariate linear regression analysis of each selected metabolites with all participants’ log(MDRD eGFR) resulted in a high linear relationship (training R2 = 0.85–0.94, root mean square errors (RMSEs) = 0.08–0.13; predictive R2 = 0.91–0.95), which was similar with that of MS-detected sCr (training R2 = 0.95, RMSE = 0.11; predictive R2 = 0.95). ***p < 0.001 β, unstandardized coefficient of linear regression. *R2 was calculated based on the log(BeGFR) against log (eGFR) using the equation of the model and data of the discovery cohort. †R2 was measured based on that using the equation of the model of the discovery cohort and data of the validation cohort.