Evaluation of Bone Biomarkers in Renal Osteodystrophy

Renal osteodystrophy (ROD) represents histological bone changes in patients with chronic kidney disease and is classified according to turnover and mineralization. This cross-sectional study evaluates several bone biomarkers and their ability to discriminate turnover and mineralization defects in hemodialysis (HD) patients. Bone-specific [BSAP] and total [tAP] alkaline phosphatase, procollagen-1 N-terminal propeptide [P1NP], C-terminal cross-linking telopeptide [CTX], intact [iPTH] and whole [wPTH] parathyroid hormone, sclerostin [SOST], fibroblast growth factor 23 [FGF-23], vitamin D, osteoprotegerin [OPG], and receptor activator of nuclear factor κB ligand [RANKL] were collected before the bone biopsy. Thirty-two patients were evaluated by bone histomorphometry, which identified mineralization defects and low and high turnover in 47%, 50%, and 41% of patients, respectively. Bone biomarkers (tAP, BSAP, CTX, P1NP) and hormones (iPTH, wPTH, and SOST) were capable of identifying low and high turnover (AUC > 0.877 and >0.857, respectively, p < 0.001). PTH plus AP had the best accuracy for identifying high turnover. BSAP > 2x, iPTH > 8x, and wPTH > 6x upper limit of normal range identified high turnover. Lower calcium values (Ca < 8.7 mg/dL) were correlated with mineralization defects. On the other hand, FGF-23, OPG, and RANKL did not impact the turnover and mineralization. While bone histomorphometry is not widely available, bone biomarkers such as BSAP, P1NP, PTH, and calcium allow the assessment of turnover and mineralization defects in HD patients. Then, using bone biomarkers may help clinicians define treatments for ROD and osteoporosis and monitor therapeutic response.