Serum Cystatin C as an Early Marker of Neutrophil Gelatinase‐associated Lipocalin‐positive Acute Kidney Injury Resulting from Cardiopulmonary Bypass in Infants with Congenital Heart Disease

Objective Acute kidney injury ( AKI ) is a common complication resulting from cardiopulmonary bypass in infants. Urinary neutrophil gelatinase‐associated lipocalin ( NGAL ) is a sensitive and specific marker of such injury. In this study, we compared the performance of serum cystatin C ( C ys C ) and serum creatinine ( C r) as early markers of renal dysfunction in infants undergoing cardiac surgery under bypass. Study Design, Setting, and Patients The study was designed as a prospective observational study. The study was conducted in the cardiac intensive care unit ( ICU ) of a tertiary, academic children's hospital in the United States. Infants (age <1 year) undergoing cardiac surgery under cardiopulmonary bypass were included in the study. Outcome Measure Acute kidney injury was defined based on postoperative urinary NGAL . Results A total of 17 infants were included in the study, and five of them developed AKI . Serum C ys C and C r levels were measured postoperatively on days 1, 2, and 3, and compared with baseline levels. On postoperative day 2, infants with AKI showed significant change from baseline in serum C ys C levels compared with non‐ AKI infants (28% vs. −9%, P = .03). The two groups did not show significant differences with respect to rise in serum C r on any of the 3 postoperative days. Serum C r on days 1 and 2 showed nonspecific increases in both AKI and non‐ AKI groups. The area under the receiver operating characteristic curve for day 2 C ys C was 0.87 (95% CI 0.67–1.00) in recognizing NGAL ‐positive AKI . Conclusions Postoperative serum C ys C appears to be a more specific and sensitive biomarker for NGAL ‐positive AKI resulting from cardiopulmonary bypass surgery in infants undergoing cardiac surgery.