Serum fibroblast growth factor 23 and kidney injury molecule-1 in the prediction of acute kidney injury in critically-ill patients

This study aimed to evaluate the value of serum intact fibroblast growth factor 23 (iFGF23), C-terminal FGF23 (cFGF23), and kidney injury molecule-1 (KIM-1) in predicting acute kidney injury (AKI) onset, severity, and renal function recovery in critically ill patients. A prospective cohort of 96 adults admitted to the intensive care unit (ICU) was analyzed. Patients were stratified into AKI (<i>n</i> = 51) and non-AKI (<i>n</i> = 45) groups based on KDIGO criteria. Serum iFGF23, cFGF23, and KIM-1 levels were measured at ICU admission. All three biomarkers were significantly elevated in AKI group compared to non-AKI group (all <i>p</i> < 0.01). Receiver operating characteristic (ROC) analysis showed that KIM-1 had the highest accuracy with an area under the curve (AUC) of 0.924 [95% confidence interval (CI) 0.866-0.983], followed by cFGF23 with an AUC of 0.779 (95% CI 0.676-0.881) and iFGF23 with an AUC of 0.672 (95% CI 0.554-0.789). Both iFGF23 (AUC 0.793, 95% CI 0.650-0.935) and cFGF23 (AUC 0.746, 95% CI 0.593-0.899) effectively predicted severe AKI (stages 2-3, <i>n</i> = 25). In contrast, KIM-1 showed no discriminative capacity (<i>p</i> > 0.05). ROC analysis indicated that none of the three biomarkers could predict renal function recovery (<i>p</i> > 0.05). Notably, KIM-1 may serve as a highly accurate marker for early AKI diagnosis, whereas serum FGF23 appears more promising for evaluating AKI severity. These complementary roles highlight the potential value of combining biomarkers to improve risk stratification in critically ill patients.