Introduction/Aims: The Acute Kidney Injury Network classification is based on small increases in serum creatinine (sCr) for stage 1. This study investigated whether changes in the urinary concentration of neutrophil gelatinase-associated lipocalin (uNGAL) could predict small increases in sCr in patients undergoing coronary angiography. Methods: The uNGAL was measured before contrast infusion and 2 and 4 h afterwards. Patients were divided into 2 subgroups: G<sub>1</sub> (n = 103), where sCr increased by <0.3 mg/dl, and G<sub>2</sub> (n = 22), where sCr increased by ≥0.3 mg/dl 48 h after the angiography. To determine the sensitivity and specificity for the absolute and relative variations of uNGAL, a receiver operating characteristic curve analysis was performed. Results: In G<sub>2</sub>, the uNGAL concentration increased over baseline values (15.9 vs. 9.2 ng/dl; p < 0.05), and it was also 2-fold higher in G<sub>2</sub> versus G<sub>1</sub> (15.9 vs. 8.0 ng/dl; p < 0.001). The uNGAL remains an independent predictor of the small increases in sCr, and, for an increase of 50% over baseline levels, it showed 60% sensitivity and 81% specificity. Conclusion: Changes in uNGAL concentration 2 h after the infusion of contrast media showed marginal sensitivity to predict small increases in sCr.
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