Bone turnover markers in the management of CKD-associated osteoporosis—a European consensus

Bone turnover abnormalities are common in chronic kidney disease (CKD) and contribute to bone fragility. Recently, the Kidney Disease: Improving Global Outcomes (KDIGO) introduced the term CKD-associated osteoporosis to describe bone fragility in CKD and highlighted the role of bone turnover markers (BTM) in clinical evaluation and management of bone fragility. However, current clinical practice guidelines lack specific treatment targets for bone turnover in the setting of CKD. The aim of this consensus was to present recommendations for the use of BTM in the management of CKD-associated osteoporosis. The consensus was conducted by members of relevant working groups of the European Renal Association (ERA), International Osteoporosis Foundation (IOF), European Foundation for Clinical Chemistry and Laboratory Medicine (EFLM) and European Society of Pediatric Nephrology (ESPN). Bone-specific alkaline phosphatase and tartrate resistant acid phosphatase isoform 5b are not renally cleared and considered reliable diagnostic tools for bone evaluation in CKD-associated osteoporosis. Both have been proposed as reference BTM in CKD by a recent international consortium. Intact N-terminal telopeptide of type I collagen can also be used in CKD. The current consensus describes methodological considerations and the clinical usefulness of BTM in risk prediction, choice of therapeutic strategy, and treatment evaluation in CKD-associated osteoporosis. Specific diagnostic ranges for bone turnover abnormalities are provided. Future research should focus on the integration of these reference BTM with other diagnostic tools, establishment of concrete treatment targets, and development of treatment strategies to reach these targets.