Neutrophil Gelatinase-Associated Lipocalin (NGAL) and cystatin C are early biomarkers of acute kidney injury associated with cardiac surgery

Acute kidney injury (AKI) is a serious complication in as much as half of the patients undergoing cardiac surgery, and early diagnosis and treatment are of the utmost importance. There is a need for robust biomarkers that can detect cardiac surgery-associated AKI (CSA-AKI) prior to rise in plasma creatinine, which typically occurs at least 48 h postoperatively. We compared pre- and 4, 12 and 48 h postoperative plasma (P) neutrophil gelatinase-associated lipocalin (NGAL), cystatin C, urea and creatinine, and urine (U) NGAL, as markers of AKI, in 49 patients (67% men, median age 65 years) scheduled for elective cardiac surgery (e.g. coronary artery bypass graft and/or valve replacement surgery) with the use of extracorporeal circulation. Patients with preoperative sepsis, renal replacement therapy, or estimated glomerular filtration rate <30 mL/min/1.73m2 were excluded. P- and U-NGAL were measured using the Roche Modular P (Roche Diagnostics®) NGAL immunoassay. According to AKIN/KDIGO criteria, nine patients (18%) were diagnosed with CSA-AKI. Compared to patients without CSA-AKI, these patients had significantly higher P-NGAL and P-cystatin C values 4 h (p-values .002 and <.001) and 12 h (p-values <.001 and <.001) postoperatively. The same differences were not observed for U-NGAL. Patients with AKI also had significantly higher P-creatinine 4 and 12 h postoperatively (p-values .001 and <.001), however the rise in P-creatinine was just above the upper reference limit. In conclusion, plasma NGAL and cystatin C seem to detect CSA-AKI earlier than the more commonly used biomarkers creatinine and urea.