P.327: Urinary vitamin D binding protein (VDBP) as a biomarker in systemic lupus erythematosus patients with lupus nephritis and its relation to renal activity.

Abstract

Introduction: The autoimmune disease systemic lupus erythematosus (SLE) can affect many systems of the body. Nearly 50% of SLE patients had lupus nephritis, that increased their risk of cardiovascular disease and kidney failure. Therefore, early diagnosis and treatment improve SLE patients’ survival. The current available urinary biomarkers are not sensitive nor specific for diagnosing LN. This study was undertaken to investigate whether urinary Vitamin D Binding Protein represents a marker of nephritis and renal activity in SLE patients. Methods: An observational Cross-sectional study was conducted with 3 study groups compromising 60 patients with biopsy proven LN (30 active LN and 30 in remission) and 20 patients with non-nephritis SLE. Spot urinary samples were collected from all participants and the levels of Urinary Vitamin D Binding Protein in urine were measured by ELISA, 24 hours urinary proteins, urinary and serum creatinine were measured. Results: Urinary Vitamin D Binding Protein was significantly higher in LN patients than in non-nephritis SLE (3.33(2.67-4.53) - 2.35(1.40-3.22) respectively) (P < 0.002),but there were no significant differences in Urinary Vitamin D Binding Protein between active LN and LN in remission group although it was slightly higher in active LN group (3.58(2.73-4.83) - 3.23(1.94-4.25) respectively) (P 0.337) as shown in figure 1. There was a significant correlation between C3 consumption and urinary Vitamin D Binding Protein. ROC curve cut-off values of urinary Vitamin D Binding Protein were (2.08-2.01-2.82), Area under curve (AUC) were (0.572-0.782-0.685), with sensitivity (SN) of (100%-100%-66.7%) 63.3%, specificity (SP) of (26.7%-50%-65%) in Active LN vs. LN with remission, Active LN vs. SLE without LN and LN with remission vs. SLE without LN respectively as shown in figure 2. Conclusion: Although urinary Vitamin D Binding Protein level was significantly higher in LN patients than in non-nephritis SLE, it failed to discriminate patients with active LN from those in remission. Further studies are still needed before considering urinary hepcidin as a non-invasive diagnostic marker of active LN.