F2 and chronic kidney disease: Of the 22 significantly different proteins selected in this study, alpha-2-HS-glycoprotein, complement C9, clusterin, β-2-microglobulin, retinol-binding protein 4, plasminogen, complement C4, prothrombin, vitamin-D-binding protein, hemopexin, transthyretin, and cystatin C were consistent with previously proposed markers for various nephropathies associated with CKD [12,15,16,17,21,24,25,34].