FGF-23 levels in patients with AKI and risk of adverse outcomes

Background and objectives Fibroblast growth factor 23 plays an important role in regulating phosphate and vitamin D homeostasis. Elevated levels of fibroblast growth factor 23 are independently associated with mortality in patients with CKD and ESRD. Whether fibroblast growth factor 23 levels are elevated and associated with adverse outcomes in patients with AKI has not been studied. Design, setting, participants, & measurements This study had 30 participants with AKI, which was defined as an increase in serum creatinine≥0.3 mg/dl or ≥50% from baseline, and 30 controls from the general hospital wards and intensive care units. Plasma levels of C-terminal fibroblast growth factor 23 and vitamin D metabolites were measured within 24 hours of AKI onset and 5 days later. The composite endpoint was death or need for renal replacement therapy. Results Enrollment fibroblast growth factor 23 levels were significantly higher among participants with AKI than controls (median [interquartile range]=1471 [224-2534] versus 263 [96-574] RU/ml, P=0.003). Enrollment fibroblast growth factor 23 correlated negatively with 25-hydroxyvitamin D (r=-0.43, P<0.001) and 1,25-dihydroxyvitamin D (r=-0.39, P=0.003) and positively with phosphate (r=0.32, P=0.02) and parathyroid hormone (r=0.37, P=0.005). Among participants with AKI, enrollment fibroblast growth factor 23 (but not other serum parameters) was significantly associated with the composite endpoint, even after adjusting for age and enrollment serum creatinine (11 events; adjusted odds ratio per 1 SD higher ln[fibroblast growth factor 23]=13.73, 95% confidence interval=1.75-107.50). Conclusions Among patients with AKI, fibroblast growth factor 23 levels are elevated and associated with greater risk of death or need for renal replacement therapy.