DENVER – Interleukin18 appears to reliably predict the need for renal replacement therapy in patients who develop acute kidney injury after cardiac surgery, according to results from a multicenter study.
While a number of biomarkers have been identified that may prove useful in determining which patients with acute kidney injury will require renal replacement therapy – especially proteins associated with inflammation, signaling, and tubular injury – these markers have not been compared and validated in a large group of patients with the condition.
Only about 10% of patients with acute kidney injury will go on to require dialysis, explained Dr. John M. Arthur of the division of nephrology at the Medical University of South Carolina, Charleston. "What we’re trying to do is figure out a test that clinicians could do in their hospitals that would help them determine which patients are likely to go on to require dialysis," he said at the annual meeting of the American Society of Nephrology. "That’s something that we don’t have right now. We’re still not there yet, but this is bringing us closer."
He presented results from a study of urine samples from 117 patients who developed at least stage 1 acute kidney injury after undergoing cardiac surgery at the Medical University of South Carolina; Duke University, Durham, N.C.; George Washington University, Washington; and the University of Tennessee, Memphis. The patients were assessed for an increase in serum creatinine of 50% or 0.3 mg/dL. The primary outcome measure was the requirement for renal replacement therapy.
Of the 117 patients, 11 required renal replacement therapy and 106 did not. Both groups were similar in gender (71% male among those who did not require renal replacement vs. 73% among those who did); age (a mean of 64 vs. 68 years, respectively); race (23% vs. 9% African American), proportion on bypass (85% vs. 73%); bypass time (2.47 hours vs. 2.36 hours), preoperative serum creatinine (1.2 vs. 1.3 mg/dL), and time of urine collection after surgery (1.4 days vs. 1.8 days).
Compared with their counterparts who did not undergo renal replacement therapy, those who did had significantly higher levels of serum creatinine at the time of collection (1.9 vs. 2.7 mg/dL) as well as mortality (3.80% vs. 72.70%).
Using a receiver operator characteristics area under the curve analysis, which is an indicator for the predictive quality of the marker, the researchers found that several markers significantly predicted the need for renal replacement therapy, including IL-18, vascular cell adhesion molecule (VCAM), N-acetyl-beta-D-glucosaminidase (NAG), IL-6, and liver-type fatty acid binding protein (L-FABP).
IL-18 was the strongest marker to predict the association, with an area under the curve of 0.86 and a positive predictive value of 60%, which Dr. Arthur said is good enough to help select patients for clinical trials in acute kidney injury.
He noted that a study of at least 1,000 patients is needed to confirm the findings.
Dr. Arthur said that he had no relevant financial conflicts to disclose. The study was funded by the National Institute of Diabetes and Digestive and Kidney Diseases and by a VA Merit award.