The impact of bone histomorphometry, bone-related biomarkers, and FRAX® on fractures patients with predialysis CKD

INTRODUCTION: Chronic kidney disease (CKD) patients are at increased risk of fracture. Whether the type of renal osteodystrophy (ROD) contributes to fracture risk is not currently established since bone biopsies are not frequently performed in clinical practice. We aimed to evaluate the association of ROD subtypes, bone biomarkers, and fracture risk assessed with the FRAX® tool with the occurrence of fractures in predialysis CKD patients. METHODS: Retrospective study with patients followed between 2014-2023. Blood tests, including bone-related biomarkers (BRB), and bone biopsies were performed at the beginning of follow-up. Data from dual x-ray absorptiometry (DXA) scan and clinically evident fractures were obtained from medical registries. Radiographs of the thoracic/lumbar spine were evaluated to detect vertebral fractures, and the FRAX® index without bone mineral density (BMD) was calculated with the web-based tool. RESULTS: Median follow-up time was 7.5 ± 3 years and 9.3% of the patients had a bone fracture, with an incidence of 12/1000 patient-year. Patients who had a fracture had higher phosphorus levels (4.1 mg/dL vs 3.5 mg/dL, p = 0.047). Histomorphometric subtypes and BRB were not associated with incidence of fractures nor with fracture risk assessed by FRAX®. There was a tendency for lower bone volume in the group with fractures (p = 0.057). FRAX® (without BMD), regardless of the inclusion of CKD as secondary osteoporosis, showed an overall good diagnostic accuracy for predicting fractures in predialysis CKD. CONCLUSION: ROD subtypes were not associated with incidence of fractures in these patients. The discriminative ability of FRAX in this population emphasizes its usefulness in CKD predialysis patients.