A method for diagnosing and/or monitoring early stage chronic kidney disease in an individual, the method comprising: (a) analyzing in vitro the pattern of posttranslational modifications of a plasma protein of an individual to be diagnosed, wherein the plasma protein is selected from the group consisting of albumin, beta-2 microglobulin (β2MG), cystatin C, transferrin, and retinol binding protein; wherein the posttranslational modification is selected from the group consisting of guanidylation of one or more lysine residue(s) of human serum albumin selected from positions K36, K44, K183, K186, K198, K205, K219, K300, K375, K383, K463, K468, K499, K548, K560, K562, K565, K569, K581, K584, K588, K597 and/or K598 as depicted in SEQ ID No. 1; glycosylation 2xHex, i.e., addition of a glucose molecule to one or more lysine residue(s) of human serum albumin selected from positions K28, K375, K460, K499, K548, K565 as depicted in SEQ ID No. 1, and subsequent addition of a further glucose molecule to the first glucose molecule; formylation of one or more lysine residue(s) of human serum albumin selected from K36, K214, K219, K223, K375, K437, K449, K558, K560, K562, K565, K569, K588, K598 as depicted in SEQ ID No. 1; oxidation of methionine 119 of beta-2 microglobulin as depicted in SEQ ID No. 3; formylation of the N-terminus of beta-2 microglobulin, carbamylation of a lysine residue or the N-terminus of beta-2 microglobulin; formylation of the N-terminus of Cystatin C, carbamylation of the N-terminus or lysine of Cystatin C; guanidylation of a lysine of transferrin; and formylation of the N-terminus of retinol binding protein; (b) comparing the posttranslational modification pattern of the plasma protein of the individual to be diagnosed with the posttranslational modification pattern of the plasma protein of an individual not suffering from CKD; (c) detecting a difference in the posttranslational modification pattern of the plasma protein of the individual to be diagnosed as compared to the posttranslational modification pattern of the plasma protein from the individual not suffering from CKD; and (d) diagnosing CKD, if the plasma protein of the individual to be diagnosed exhibits at least one posttranslational modification according to a) above that is absent in the plasma protein of the individual not suffering from CKD. (a) analyzing in vitro the pattern of posttranslational modifications of a plasma protein of an individual to be diagnosed, wherein the plasma protein is selected from the group consisting of albumin, beta-2 microglobulin (β2MG), cystatin C, transferrin, and retinol binding protein; wherein the posttranslational modification is selected from the group consisting of guanidylation of one or more lysine residue(s) of human serum albumin selected from positions K36, K44, K183, K186, K198, K205, K219, K300, K375, K383, K463, K468, K499, K548, K560, K562, K565, K569, K581, K584, K588, K597 and/or K598 as depicted in SEQ ID No. 1; glycosylation 2xHex, i.e., addition of a glucose molecule to one or more lysine residue(s) of human serum albumin selected from positions K28, K375, K460, K499, K548, K565 as depicted in SEQ ID No. 1, and subsequent addition of a further glucose molecule to the first glucose molecule; formylation of one or more lysine residue(s) of human serum albumin selected from K36, K214, K219, K223, K375, K437, K449, K558, K560, K562, K565, K569, K588, K598 as depicted in SEQ ID No. 1; oxidation of methionine 119 of beta-2 microglobulin as depicted in SEQ ID No. 3; formylation of the N-terminus of beta-2 microglobulin, carbamylation of a lysine residue or the N-terminus of beta-2 microglobulin; formylation of the N-terminus of Cystatin C, carbamylation of the N-terminus or lysine of Cystatin C; guanidylation of a lysine of transferrin; and formylation of the N-terminus of retinol binding protein; (b) comparing the posttranslational modification pattern of the plasma protein of the individual to be diagnosed with the posttranslational modification pattern of the plasma protein of an individual not suffering from CKD; (c) detecting a difference in the posttranslational modification pattern of the plasma protein of the individual to be diagnosed as compared to the posttranslational modification pattern of the plasma protein from the individual not suffering from CKD; and (d) diagnosing CKD, if the plasma protein of the individual to be diagnosed exhibits at least one posttranslational modification according to a) above that is absent in the plasma protein of the individual not suffering from CKD.