Urinary N-Acetyl-beta-D-glucosaminidase as an Early Marker for Acute Kidney Injury in Full-Term Newborns with Neonatal Hyperbilirubinemia

PURPOSE To investigate renal function estimated by markers in full-term newborns with hyperbilirubinemia. METHODS A total of 332 full-term newborns with hyperbilirubinemia and 60 healthy full-term newborns were enrolled. Total serum bilirubin, serum creatinine (Cr), serum blood urea nitrogen (BUN), serum cystatin C (Cys-C), urinary beta-2-microglobulin (β 2MG) index, and urinary N-acetyl-beta-D-glucosaminidase (NAG) index were measured before and after treatment. All newborns were divided into three groups according to total serum bilirubin levels: group 1 (221-256), group 2 (256-342), and group 3 (>342). RESULTS The control group and group 1 did not differ significantly in regard to serum Cr, serum BUN, serum Cys-C, urinary β 2MG index, and urinary NAG index. Urinary NAG index in group 2 was significantly higher than that in control group (P < 0.001). Between control group and group 3, serum Cys-C, urinary β 2MG index, and urinary NAG index differed significantly. The significant positive correlation between total serum bilirubin and urinary NAG index was found in newborns when total serum bilirubin level was more than 272 μmol/L. CONCLUSIONS High unconjugated bilirubin could result in acute kidney injury in full-term newborns. Urinary NAG might be the suitable marker for predicting acute kidney injury in full-term newborns with hyperbilirubinemia.