NGAL levels in blood and urine in early diagnosis of acute renal injury after cardiac surgery

Objective To investigate the clinical value of NGAL levels in blood and urine in the early diagnosis of acute renal injury after cardiac surgery. Methods From January, 2014 to December, 2017, 120 patients undergoing cardiac surgery at our hospital were selected. Their blood and urine samples were collected before and after the operation. The levels of neutrophil gelatinase-related lipid-carrying eggs (NGAL) in blood and urine as well as serum creatinine (Scr) were measured. According to the results, the patients were divided into an acute kidney injury group (AKI group) and non-acute kidney injury group (non-AKI group). The levels of NGAL in blood and urine as well as Scr were measured before the operation and at different time points after the operation. The diagnostic value of NGAL (blood and urine) in AKI was evaluated by ROC. Results The levels of NGAL in blood and urine 2, 61, 12, and 24 h after the operation in the AKI group were significantly different from those before the operation (baseline value) and those in the non-AKI group (all P<0.05). The NGAL level got to the peak 6 h after the operation in blood and 2 h in urine (both P<0.05). The sensitivity, specificity, positive and negative predictive values, the area under curve (AUC), and 95% CI of NGAL in blood 6 h after the operation were 73.4%, 75.8%, 61.4%, 62.4%, 0.782, and 0.346-0.954; and those of NGAL in urine 2 h after the operation were 86.7%, 92.4%, 68.7%, 72.5%, 0.894, and 0.462-0.948. Conclusions NGAL levels in blood and urine can be used as markers for the early diagnosis of AKI after cardiac surgery, and have important clinical value. Key words: Blood NGAL; Urine NGAL; Cardiac surgery; Acute kidney injury