Urine biomarker could diagnose acute kidney injury

The presence of certain markers in the urine might be a red flag for acute kidney injury, according to a study published in the Nov. 11 online edition of the Journal of the American Society of Nephrology. The results suggest that a simple urine test could help prevent cases of kidney failure.

Acute kidney injury involves the rapid loss of kidney function. It affects up to 7 percent of hospital patients overall and 25 percent to 30 percent of intensive care patients. Unlike heart or brain injuries, which show obvious outward signs, physical symptoms are not typically present with AKI. Researchers have been looking for biomarkers of AKI, with the hope that early detection will lead to early therapy to prevent kidney failure.

Lead author Dr. Richard Zager of the Clinical Research Division, with Dr. Ali Johnson in his lab and colleagues from UW Medicine, Seattle Children’s and Vanderbilt University Medical Center, investigated whether certain molecules that are produced during injury and infection might be excreted in the urine and serve as diagnostic markers. Specifically, they measured the diagnostic potential of monocyte chemoattractant protein-1, a protein that plays a role in recruiting immune cells to injured or infected sites in the body. This protein has been found in the joints of people with rheumatoid arthritis and in the urine of people with lupus.

The investigators found elevated levels of the protein as well as its messenger RNA in urine samples from both a small animal model and in human patients with AKI. This suggests that the gene that encodes this mRNA and protein is activated in patients with AKI. Using a novel technique, the investigators were also able to show changes in proteins (known as histones) that can activate the gene that produces MCP-1. This is the first time that the ability to detect these protein modifiers have been identified in human urine samples.

“This is a new diagnostic test that provides information about what processes are actually inducing acute kidney injury,” Zager said. “However, a much larger prospective study is required to ultimately determine its clinical utility.”

[Adapted from an American Society of Nephrology news release]