Urinary biomarkers and acute kidney injury in children: the long road to clinical application.

Pediatric acute kidney injury is rising with the advances in technology available for children with chronic conditions or those who are critically ill. Serum creatinine and urine output, traditional markers of renal function, often allow only delayed and unreliable diagnosis of acute kidney injury. Biomarker development in pediatric patients with low disease prevalence is challenging (small cohorts, few analyzable events). In this issue of Pediatric Nephrology, Ivanisevic and colleagues report that urinary liver-type fatty-acid-binding protein (L-FABP) can be used for early identification of pediatric acute kidney injury in a small cohort undergoing cardiac surgery. Addition of the biomarker resulted in an improvement in early diagnosis compared with a clinical model (age, gender, body weight, cardiopulmonary bypass duration, and aortic clamp time). It is noteworthy that the preoperative clinical model performed excellently in predicting postsurgery pediatric acute kidney injury. Further work is needed before this or other novel biomarkers (alone or in combination) can be implemented in clinical practice. Large-scale observational studies are needed to test these biomarkers against hard clinical endpoints, independent of serial measurements of serum creatinine concentrations. Prospective randomized interventional trials using exclusively high biomarker levels to define acute kidney injury should demonstrate improved clinical outcomes.