Kidney Injury after Surgery May be Predicted by use of Biomarkers
Acute kidney injury (AKI) is a frequent complication of cardiac surgery which can result in other complications or even death. Three protein measurements (biomarkers) have been found to indicate who has a high risk of developing kidney injury after heart surgery, according to two studies appearing in an upcoming issue of the Journal of the American Society of Nephrology.
The incidence of AKI has risen significantly over the past 15 years. Between 1988 and 2002, the incidence of AKI in the community increased from 61 to 500 per 100,000 population.
"To date, these are the largest studies in adults and children comparing and validating the performance of three of the most frequently studied markers of kidney injury," said author Chirag Parikh, MD, PhD (Yale University School of Medicine).
The two studies come from the TRIBE-AKI consortium which was formed in 2005 to develop and validate novel biomarkers of AKI, as they progress from the discovery phase to patient care. The consortium consists of a group of investigators at over 10 academic institutions in the United States and Canada.
The researchers conducted the prospective, multicenter cohort studies involving 1219 adults and 311 children undergoing heart surgery throughout North America. Frequent urine and blood samples were collected to measure levels of three proteins -- urine interleukin-18 (IL-18) and urine and plasma (blood) neutrophil gelatinase-associated lipocalin (NGAL)—and assess their ability to predict who will develop kidney injury after surgery.
Traditionally, kidney trouble is assessed by measuring the blood protein creatinine , which is not ideal because it has a delayed result—it does not pick up early damage and injury to the kidneys. AKI is considered severe when creatinine doubles.
"We demonstrated that the three proteins in our study identify kidney injury soon after surgery and 24 to 48 hours earlier than creatinine, and shows a similar result," according to Parikh.
Risk of kidney injury was especially high—more than six times higher—for adults and children with the highest levels of urine IL-18. Plasma NGAL also predicted kidney injury in adults, whereas urine NGAL was not an accurate predictor in adults once results were adjusted for other factors. Urine IL-18 and urine, but not plasma, NGAL were accurate predictors in children.
Doctors may wish to measure these urine or blood proteins immediately after surgery to predict which patients are at high risk of developing kidney injury. These patients might benefit from kidney protective therapies.
The studies' results could also transform the diagnosis of kidney disease, Parikh believes. "Developing markers of structural kidney damage, before kidney function fails, is a top priority," he said.
The research's main limitation was that the adults enrolled were mainly Caucasian. Future studies should consider whether the results are the same in other races.
Postoperative Biomarkers Predict Acute Kidney Injury and Poor Outcomes after Adult Cardiac Surgery; Chirag R. Parikh, Steven G. Coca, Heather Thiessen-Philbrook, Michael G. Shlipak, Jay L. Koyner, Zhu Wang, Charles L. Edelstein, Prasad Devarajan, Uptal D Patel, Michael Zappitelli, Catherine D. Krawczeski, Cary S. Passik, Madhav Swaminathan, Amit X. Garg, and for the TRIBE-AKI Consortium; JASN Aug 11, 2011 ASN.2010121302; published ahead of print August 11, 2011, doi:10.1681/ASN.2010121302
Postoperative Biomarkers Predict Acute Kidney Injury and Poor Outcomes after Pediatric Cardiac Surgery; Chirag R. Parikh, Prasad Devarajan, Michael Zappitelli, Kyaw Sint, Heather Thiessen-Philbrook, Simon Li, Richard W. Kim, Jay L. Koyner, Steven G. Coca, Charles L. Edelstein, Michael G. Shlipak, Amit X. Garg, Catherine D. Krawczeski, and for the TRIBE-AKI Consortium; JASN Aug 11, 2011 ASN.2010111163; published ahead of print August 11, 2011, doi:10.1681/ASN.2010111163