Diagnostic and Prognostic Value of Fibroblast Growth Factor 23 (FGF-23) in Critically Ill Patients with AKI

Background: To evaluate serum FGF23 as a diagnostic and prognostic biomarker in AKI among critically ill patients. Methods: This prospective cohort included 190 ICU patients,stratified into AKI (n=100) and non-AKI (n=90) groups per KDIGO criteria within 7 days of admission. The AKI group was further subclassified by renal recovery status at discharge. Serum iFGF23 and cFGF23 levels were measured within 24 hours of ICU admission, along with baseline clinical biomarkers. Univariate and multivariate logistic regression identified AKI risk factors. FGF23's predictive performance was assessed via ROC analysis. Results: No intergroup differences were observed in demographic characteristics or baseline comorbidities (all P>0.05). AKI patients demonstrated significantly higher serum creatinine, neutrophil percentage, and phosphate levels alongside lower eGFR, albumin, and calcium levels (P<0.05). Serum cFGF23 was substantially elevated in AKI patients (69.90 [30.68–228.12] vs 33.85 [23.02-66.43] RU/mL, P<0.001), with no difference in iFGF23 levels (P=0.653). The cFGF23/iFGF23 ratio was significantly increased in AKI (4.77 [2.14-13.88] vs 2.41 [1.36-3.46], P<0.001). Multivariate analysis confirmed hypocalcemia and elevated cFGF23 as independent AKI predictors. ROC analysis revealed cFGF23's diagnostic utility (AUC 0.72, sensitivity 60.6%, specificity 72.2%), which improved to 85.6% specificity when combined with creatinine. Conclusion: Serum cFGF23 independently predicts AKI and complements creatinine-based diagnosis. Their combination enhances diagnostic specificity, offering clinical utility for early AKI detection in critical care.