2.3 Definition of chronic kidney disease
CKD was defined according to the latest guidelines of the American Diabetes Association Standards of Medical Care20. First morning spot urine samples were collected for determination of the urine albumin-to-creatinine ratio (UACR). Urine albumin was measured by a chemiluminescence immunoassay (Siemens Immulite 2000, United States), and creatinine was measured by the Jaffe’s kinetic method (Biobase-Crystal, Jinan, China) using an automatic analyzer. UACR was calculated by dividing the urine albumin concentration by the urine creatinine concentrations, and the result was expressed in mg/g. CKD was defined as a UACR ≥ 30 mg/g or an eGFR < 60 mL/min/1.73 m2.