The importance of serum neutrophil gelatinase-associated lipocalin level in patients with lupus nephritis

Introduction: The neutrophil gelatinase-associated lipocalin (NGAL) has emerged as a biomarker of renal damage. Objectives: The aim of this study was to assess the serum levels of NGAL (sNGAL) as a marker of disease activity in individuals with lupus nephritis (LN). Patients and Methods: This study contained 50 systemic lupus erythematosus (SLE) individuals with (n = 25) and without (n = 25) nephritis, and 39 healthy controls. The sNGAL levels were measured by ELISA. Renal function test, urinary parameters, lupus serology activity, and also calculated SLE disease activity index (SLEDAI) were analyzed to determine their associations with sNGAL. Results: The results revealed that the SLE individuals with or without nephritis had a raised serum NGAL levels as compared to control subjects (P < 0.001). Additionally, sNGAL levels in LN individuals were meaningfully higher compared to those in non-LN patients (P < 0.001). Serum NGAL showed a significant correlation with the SLEDAI, serum creatinine, and 24-h urinary protein (P< 0.05). More importantly, sNGAL had a significant positive correlation with the activity index of LN (r = 0.616, P = 0.001). In the ROC curve analysis, the measurement of sNGAL level showed a good diagnostic performance for distinguishing individuals with LN from SLE patients without renal involvement with AUC = 0.902 (P < 0.001), 72% sensitivity, and 99% specificity. Moreover, sNGAL could identify all of SLE patients from controls with high accuracy, AUC= 0.99, P< 0.001, with 99% sensitivity, and 97% specificity. Conclusion: Serum NGAL had an association with clinical parameters and could discriminate LN from SLE patients without renal involvement. Our result suggests that serum NGAL can be used for early diagnosis of LN and identifying active LN.