BGLAP and diabetic kidney disease: The area under the curve (AUC) of 25-hydroxy-vitamin D, PTH, BGP, β-CTX, T-PINP and ultrasound BMD were 0.910, 0.826, 0.841, 0.822, 0.821, 0.811 respectively in the diagnosis of early diabetic nephropathy, and the AUC of combined diagnosis was 0.995.