Association of Urinary Lipocalin-۲ 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-۲ 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-۲, values were measured and reported according to urinary lipocalin-۲/creatinine. Urinary lipocalin-۲/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-۲/creatinine value of patients with biopsy-proven LN was ۲.۹۹ ± ۴.۱ ng/mg, and in non-LN patients was ۱.۱۶ ± ۱.۲۷ ng/mg. Urinary lipocalin-۲/creatinine levels in LN patients were significantly higher than those in non-LN patients (P- Value = ۰.۰۳). In LN patients, urinary lipocalin-۲/creatinine significantly correlated with proteinuria (r = ۰.۶۸; P = ۰.۰۰۰۱). Using a cutoff value of ۰.۸۹۶ ng/mg, urinary lipocalin-۲/creatinine had a sensitivity of ۸۹.۷% and a specificity of ۳۹.۱% for identifying SLE patients with biopsy-proven LN. The area under the ROC curve was ۰.۶۶۴ ± ۰.۰۷۶ with a ۹۵% confidence interval of ۰.۵۲-۰.۸۱ (P=۰.۰۴). Analysis of variance showed that urinary lipocalin-۲/creatinine is the same in different classes of LN (P-value=۰.۲۸). Conclusion: An important clinical conclusion is that measurement of urinary Lipocalin-۲ may result in earlier diagnosis of LN.