University of Alabama at Birmingham researchers have found that the amount of proteins excreted in the urine of preterm infants with acute kidney injury differs from amounts found in infants with normal kidney function, and may be a marker of kidney damage in premature babies. The study, “Acute Kidney Injury Urine Biomarkers in Very Low-Birth-Weight Infants,” was published in the Clinical Journal of the American Society of Nephrology.

“The findings in this study could help physicians better diagnose kidney health in newborns,” David Askenazi, an associate professor in the UAB Department of Pediatrics, director of UAB’s Pediatric and Infant Center for Acute Nephrology and study author, said in a recent news release. “Having better diagnostic tests to diagnose kidney injury will have an important impact on how we care for infants and how we prognosticate outcomes, and will enable us to design studies to prevent and/or mitigate kidney damage in these very vulnerable babies.”

Approximately 25 percent of preterm infants develop acute kidney injury (AKI), a sudden decline in kidney function, making early detection important. Babies with AKI are known to need longer stays in hospitals and to have a lower chance of survival. Premature infants are also at high risk of chronic kidney disease, potentially caused by AKI.

Serum creatinine (SCr) levels are usually evaluated to determine AKI but have important limitations, and urine biomarkers may improve the ability to detect kidney damage.

Researchers examined the association between 14 different urine biomarkers and AKI in premature infants. The team collected a drop of urine from 113 of these infants and measured the 14 proteins. They found that infants with AKI had higher maximum levels of urine clusterin, cystatin C, osteopontin, neutrophil gelatinase-associated lipocalin, and α-glutathione S-transferase compared to infants without AKI. In addition, infants with AKI had lower minimum levels of epithelial growth factor and uromodulin than those without AKI.

Further studies are necessary to determine whether these biomarkers can predict clinical outcomes, the researchers said. In addition, intervention studies that use biomarkers to stratify enrollment groups are needed before bedside evaluations can be incorporated into care.

“Additional studies to determine how AKI contributes to chronic kidney disease in these newborns are underway,” Askenazi said. “Improving our ability to diagnose AKI accurately is critical to improving our understanding of the natural course of disease and developing strategies to improve outcomes.”