Pentosidine, S100A12/ENRAGE, RAGE, and myeloperoxidase were measured by well-validated methods (see Materials and Methods) with very good intra- and interassay variability (<10%), and thorough analysis of the mutual correlations among these compounds showed consistent internal relationships suggesting that these biomarkers reflect AGE/RAGE status in CKD patients. The gene discussed is MPO; the disease is chronic kidney disease.