RBP4 and diabetic kidney disease: We assessed 11 urinary biomarkers finally, including α1-MG, β2-MG, RBP4, EGF, KIM-1, VDBP, CysC, nephrin, TNFR-1, TNFR-2, and TIMP-1, to establish a set of sensitive, non-invasive markers that can be detected simultaneously for the early detection of DKD.