New test tells if kidney damage is acute or chronic

New test tells if kidney damage is acute or chronic

Your patient's serum creatinine, the current diagnostic test for renal failure, is elevated to 2.0. This could be due to volume depletion, chronic kidney disease that the patient has had for years, or acute kidney injury.

In the case of volume depletion, the patient might be hydrated and sent home. In the case of chronic stable kidney failure, the creatinine level of 2.0 might be put aside as nonessential issue in the case, says Jonathan Barasch, MD, PhD, an associate professor of medicine at Columbia University Medical Center in New York City.

But in the case of acute kidney injury, the patient has a serious illness with high morbidity and mortality and needs to be admitted immediately, says Barasch.

A new blood test focuses on a protein found in the urine in the event of sudden kidney failure, NGAL (neutrophil gelatinase-associated lipocalin). When researchers looked at more than 600 patients who came to the ED at New York Presbyterian Hospital in New York City, researchers found NGAL levels in patients later diagnosed with acute kidney failure were 30 times higher than patients who did not have renal injury.¹

Currently, an elevated serum creatinine level, which can reveal kidney damage, might take one to two days to accumulate. It also doesn't indicate the cause of the damage: an underlying infection, previously active kidney disease, or an emergent medication reaction.

"NGAL was diagnostic in a single test, whereas a single serum creatinine test can't discriminate acute kidney failure from chronic kidney disease," explains Barasch, one of the study's authors.

For volume depletion or chronic kidney disease, NGAL levels are negligible, but in acute kidney injury, they are extremely elevated. For all of these conditions, however, serum creatinines would be identical. "Creatinine is a marker of steady-state renal dysfunction, not acute renal dysfunction," says Barasch. NGAL, on the other hand, is a protein that is necessary to defend the kidney at times of acute damage. Its measurement tells us that an acute inflammatory event is incipient in the kidney."

Barasch says he expects a commercial test to be available in the coming year. "ED nurses could then take a sample for NGAL measurements and obtain within the hour the information to suggest that the patient has acute renal failure and consequently should be admitted to the hospital for further work-up," he says.

Reference

1. Nickolas TL, O'Rourke MJ, Yang J, et al. Sensitivity and specificity of a single emergency department measurement of urinary neutrophil gelatinase-associated lipocalin for diagnosing acute kidney injury. Ann Intern Med 2008; 148:810-819.