Determinants of fibroblast growth factor-23 and parathyroid hormone variability in dialysis patients

Treatment strategies for abnormal mineral metabolism in chronic kidney disease are largely based on achieving target ranges of biomarkers that vary considerably over time, yet determinants of their variability are poorly defined.

Observational study including 162 patients of three dialysis cohorts (peritoneal dialysis, n = 78; hemodialysis, n = 49; hemodiafiltration, n = 35). Clinical and biochemical determinants of parathyroid hormone (PTH) and fibroblast growth factor-23 (FGF23) variability were analyzed in the peritoneal dialysis cohort. All cohorts were used for comparison of PTH and FGF23 intra-subject variability (intra-class correlation), and their intra-subject variability in different modes of dialysis was explored.

High PTH variability was independently associated with lower 25-hydroxyvitamin D concentration and factors of lipid and glucose metabolism, whereas high FGF23 variability was mainly associated with lower baseline serum phosphorous. These results were consistent in multivariate and sensitivity analyses. The intra-subject variability of FGF23 was lower than for PTH irrespective of dialysis mode.

Baseline vitamin D status and serum phosphorous are independent determinants of the longitudinal variation in PTH and FGF23, respectively. The clinical utility of FGF23 measurement remains unknown, yet it appears favorable based on its greater temporal stability than PTH in dialysis patients.