Association of Urinary Lipocalin-2 with Lupus Nephritis

Objective(s): Lupus nephritis (LN) is the main cause of mortality and disability in systemic lupus erythematosus (SLE) patients. Therefore, utilizing a reliable and non-invasive method for serial measurements of renal function seems to be necessary. The aim of this study was to evaluate the role of urinary lipocalin-2 as a biomarker of renal involvement in SLE patients. Materials and Methods: Fifty two lupus patients in this cross sectional study were divided into two groups: patients with and without nephritis. For each group, urinary lipocalin-2, values were measured and reported according to urinary lipocalin-2/creatinine. Urinary lipocalin-2/creatinine sensitivity and specificity for identifying biopsy-proven nephritis were calculated, and a receiver operating characteristic (ROC) curve was constructed. Results: The mean urinary lipocalin-2/creatinine value of patients with biopsy-proven LN was 2.99 ± 4.1 ng/mg, and in non-LN patients was 1.16 ± 1.27 ng/mg. Urinary lipocalin-2/creatinine levels in LN patients were significantly higher than those in non-LN patients (P- Value = 0.03). In LN patients, urinary lipocalin-2/creatinine significantly correlated with proteinuria (r = 0.68; P = 0.0001). Using a cutoff value of 0.896 ng/mg, urinary lipocalin-2/creatinine had a sensitivity of 89.7% and a specificity of 39.1% for identifying SLE patients with biopsy-proven LN. The area under the ROC curve was 0.664 ± 0.076 with a 95% confidence interval of 0.52-0.81 (P=0.04). Analysis of variance showed that urinary lipocalin-2/creatinine is the same in different classes of LN (P-value=0.28). Conclusion: An important clinical conclusion is that measurement of urinary Lipocalin-2 may result in earlier diagnosis of LN.