GPC4 and chronic kidney disease: GPC4 showed higher area under the curve (AUC) values for the diagnosis of eGFR < 60 mL/min/1.73 m2, albuminuria, and CKD at baseline as well as at follow up compared to uromodulin and FGF23 and, therefore, outperformed these markers for the diagnosis of baseline and future kidney function (Supplemental Table S2).