Urinary neutrophil gelatinase–associated lipocalin, a biomarker for systemic inflammatory response syndrome in patients with nephrolithiasis

Abstract Background The objective of this study was to determine the diagnostic value of neutrophil gelatinase–associated lipocalin (NGAL), C-reactive protein (CRP), and procalcitonin (PCT) in the prognosis of patients presenting with the systemic inflammatory response syndrome (SIRS) with nephrolithiasis. Methods Urine NGAL protein levels were measured by enzyme-linked immunosorbent assay in 87 patients presenting with nephrolithiasis who were diagnosed as SIRS. Additionally, 52 patients presenting with nephrolithiasis but without urinary tract infection and 30 healthy controls were also included in the study. Levels of serum CRP and PCT were also taken into consideration. Results Median urinary NGAL levels were significantly increased in the SIRS cohorts compared with nephrolithiasis without urinary tract infection patients (4.28 ng/mL versus 2.69 ng/mL, P < 0.001), and NGAL was markedly elevated even in the early stage of SIRS (3.23 ng/mL versus 2.69 ng/mL, P < 0.001). According to the receiver-operating characteristic analysis, NGAL demonstrated a high diagnostic value compared with either PCT or CRP. In the later stage of SIRS, NGAL remained a highly sensitive (76.8%) and specific (86.5%) diagnostic marker compared with either PCT or CRP. Moreover, the area under the curves of NGAL (0.822) were also superior to those seen in either PCT (0.657) or CRP (0.761). Conclusion Urinary NGAL is a highly sensitive and specific predictor of SIRS for patients presenting with nephrolithiasis. Further study of NGAL as a reliable biomarker of SIRS is required.