Supplementary Material for: Bone Turnover, Mineralization, and Volume Estimated by ¹⁸F-Sodium Fluoride PET/CT and Biomarkers in Chronic Kidney Disease: Mineral and Bone Disorder Compared with Bone Biopsy

Introduction: Invasive bone biopsy to assess bone metabolism in patients with chronic kidney disease-mineral and bone disorder may be replaced by the noninvasive ¹⁸F-NaF PET/CT and biomarkers of bone metabolism. We aimed to compare parameters of bone turnover, mineralization, and volume assessed by bone biopsies with results derived from ¹⁸F-NaF PET/CT and biomarkers (bone-specific alkaline phosphatase, osteocalcin, fibroblast growth factor 23, and osteoprotegerin). Methods: A cross-sectional study included 17 dialysis patients, and results from ¹⁸F-NaF PET/CT scans and the biomarkers were directly compared with the results of histomorphometric analyses of tetracycline double-labeled trans-iliac bone biopsies. Results: Bone biopsies showed 40% high, 20% normal, and 40% low bone turnover. No biopsies had generalized abnormal mineralization, and the bone volume/total tissue volume was low in 80% and high in 7%. The pelvic skeletal plasma clearance (K_i) from ¹⁸F-NaF PET/CT correlated with bone turnover parameters obtained by bone biopsy (activation frequency: r = 0.82, p < 0.01; bone formation rate/bone surface: r = 0.81, p < 0.01), and K_i defined low turnover with high sensitivity (83%) and specificity (100%). CT-derived radiodensity correlated with bone volume, r = 0.82, p < 0.01. Of the biomarkers, only osteocalcin showed a correlation with turnover assessed by histomorphometry. Conclusion: In conclusion, ¹⁸F-NaF PET/CT may be applicable for noninvasive assessment of bone turnover and volume in CKD-MBD.