Assessment of bone turnover markers to predict mineral and bone disorder in patients with predialysis non-diabetic chronic kidney disease

Introduction: Chronic kidney disease (CKD) is commonly associated with disturbances in mineral metabolism and bone disease (MBD). Bone biopsy is the gold standard in diagnosing CKD-MBD. Hence the search for non-invasive assessment of bone health gains importance. Aims and objectives: We undertook to assess the bone health [25-hydroxyvitamin D, bone ALP (BALP), intact parathyroid hormone (iPTH) and bone mineral density (BMD)] in patients with stage 4 and 5 CKD, and to compare with healthy controls and further to correlate the markers of bone health with MBD and disease severity in CKD. Materials and methods: We recruited 45 subjects with Stage 4 and 5 CKD and 45 age-and-gender-matched controls. 25-hydroxyvitamin D, iPTH, and BALP were assayed using commercially available ELISA kits. Bone mineral density (BMD) was estimated using Dual-energy X-ray absorptiometry (DEXA). Results: CKD with MBD is associated with significantly higher levels of BALP and iPTH, and lowered 25-hydroxyvitamin D and BMD when compared to controls. iPTH and BALP showed a significant negative correlation with BMD. In the multivariate linear regression model, BALP emerged as an independent predictor of BMD. Receiver Operator Characteristics analysis showed both iPTH and BALP have significant predicting power. The combination of BALP and iPTH increased both the sensitivity and specificity resulting in a higher likelihood ratio of predicting MBD in CKD, than either marker when used alone. Conclusion: Thus BALP is an independent predictor of MBD in CKD and the combination of BALP with iPTH may be a more reliable index for non-invasive assessment of bone health in CKD.