Diagnostic and Prognostic Utility of Urinary β2 Micro globulin, Serum Creatinine, and Urine Output for Detection of Acute Kidney Injury in Critically Ill Neonates

Background: Early recognition and management of renal dysfunction are crucial in critically ill neonates, as acute kidney injury (AKI) independently increases morbidity and mortality.Objective: To evaluate the diagnostic and prognostic value of urinary β2-microglobulin (β2-MG), serum creatinine (SCr), and urine output in identifying AKI among neonates admitted to the NICU.Patients and Methods: This study included 65 full-term and preterm neonates admitted to the NICU of Damietta Specialized Hospital, Ministry of Health, Egypt, between April 2022 and September 2023. AKI was diagnosed according to the modified KDIGO neonatal criteria. Urine output and laboratory measurements of SCr and urinary β2-MG were obtained on days 2 and 7.Results: Urine output significantly decreased from day 2 to day 7 (2.90 vs. 1.00 mL/kg/h; p < 0.001). On day 2, SCr correlated positively with urinary β2-MG (r = 0.280, p = 0.024). On day 7, urine output correlated negatively with SCr (r = −0.519, p < 0.001). Serum creatinine showed strong predictive accuracy for AKI (AUC = 0.846, p < 0.001) with an optimal cutoff of 0.95 mg/dL, yielding 75.7% sensitivity and 82.1% specificity. Urine output on day 7 demonstrated excellent predictive power (AUC = 0.964, p < 0.001) with a cutoff <1.05 mL/kg/h, achieving 94.6% sensitivity and 92.9% specificity.Conclusion: Urine output and SCr measured on day 7 are reliable predictors of AKI in neonates, while urinary β2-microglobulin has limited diagnostic value.