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

<b><i>Introduction:</i></b> 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). <b><i>Methods:</i></b> 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. <b><i>Results:</i></b> 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: <i>r</i> = 0.82, <i>p</i> &#x3c; 0.01; bone formation rate/bone surface: <i>r</i> = 0.81, <i>p</i> &#x3c; 0.01), and K_i defined low turnover with high sensitivity (83%) and specificity (100%). CT-derived radiodensity correlated with bone volume, <i>r</i> = 0.82, <i>p</i> &#x3c; 0.01. Of the biomarkers, only osteocalcin showed a correlation with turnover assessed by histomorphometry. <b><i>Conclusion:</i></b> In conclusion, ¹⁸F-NaF PET/CT may be applicable for noninvasive assessment of bone turnover and volume in CKD-MBD.