Urinary N-acetyl-beta-d-glucosaminidase (NAG) is also considered as a potential early biomarker for DKD (161).A cross-sectional study shows that u-NGAL and RBP-4 are potential markers of tubular damage which can be used as complementary measurements to albuminuria and GFR in the early diagnosis of DKD (162). Here, RBP4 is linked to diabetic kidney disease.