The Levels And Significance Of Serum And Urinary NGAL In Patients With Systemic Lupus Erythematosus

Objective: To study the levels and clinical significance of serum and urinary neutrophil-gelatinase-associated lipocalin ( NGAL ) in patients with systemic lupus erythematosus(SLE).Methods: Thirty-one Chinese SLE patients(2 males and 29 females, the average age was 37. 00±12.35 years)were recruited during July 2009 to December 2009. The SLE disease activity index(SLEDAI) score was used to assess disease activity in all patients. Renal involvement was assessed with the renal SLEDAI, which consists of the 4 kidney-related parameters: hematuria, proteinuria, pyuria and urinary casts. Each item in the renal SLEDAI is assigned 4 points. Thus, scores for the renal SLEDAI can range from 0 to a maximum of 16. And the patients were divided into different groups according to renal involvement and anti-dsDNA antibody: 15 patients with nephritis and 16 patients without nephritis; 20 patients with positive anti-dsDNA antibody and 11 patients with negative anti-dsDNA antibody. Twenty sex- and age-matched healthy Chinese volunteers were recruited as normal controls. Concentrations of NGAL in serum and urinary were measured by Enzyme linked immunosorbent essay(ELISA).The clinical and laboratory data of the patients were collected. Urinary NGAL concentrations were normalized to creatinine, unless stated otherwise, with results expressed as nanograms of urinary NGAL per milligram of urinary creatinine. The methods of statistical analysis include Independent-Samples T test, One-Way ANOVA, linear correlation, linear regression and Spearman's rank correlation. SPSS13.0 was used for statistical analysis. P values less than 0.05 were considered significant.Results:1. The levels of serum NGAL in SLE patients were significantly increased than normal controls(P<0.01). And whereas no significant difference in serum NGAL levels was seen between patients without nephritis and control individuals, patients with nephritis had significantly higher NGAL levels as compared with normal controls(P<0.01). Compared with patients with and without nephritis, the levels of serum NGAL in patients with nephritis were significantly increased than those without nephritis(P<0.01).2. There was no correlation between serum NGAL and the total SLEDAI(r=0. 12,P=0. 51). No correlation was found between serum NGAL and the extrarenal SLEDAI(r=-0. 05,P=0. 79). There was no correlation between serum NGAL and the renal SLEDAI(r=0. 34,P=0. 06)3. The levels of urinary NGAL in SLE patients were significantly increased than normal controls(P<0.05). And whereas no significant difference in urinary NGAL levels was seen between patients without nephritis and control individuals, patients with nephritis had significantly higher NGAL levels as compared with normal controls(P<0.01). Compared with patients with and without nephritis, the levels of urinary NGAL in patients with nephritis were significantly increased than those without nephritis(P<0.01).4. Urinary NGAL had a significant association with the total SLEDAI(r=0. 38,P=0. 04). In SLE patients, there was a stronger correlation between urinary NGAL and the renal SLEDAI(r=0. 82,P<0.01). No correlation was found between urinary NGAL and the extrarenal SLEDAI(r=-0. 03,P=0. 86).5. There were no significant differences in serum and urinary NGAL levels between patients with positive anti-dsDNA antibody and patients with negative anti-deDNA antibody.6.There was no relationship between the levels of serum and urinary NGAL and some clinical indexes (including age, weight, estimated glomerular filtration rate, hemoglobin, the count of white blood cell, platelets, complement, albumin, globulin, urea nitrogen, serum creatinine, IgG, IgA, IgM). Urinary NGAL levels had a strong and significant correlation with Upro:Ucre values(r=0. 62,P<0.01).7. The levels of serum NGAL had a significant association with urinary NGAL in patients with SLE(r=0.46,P<0.01). Conclusions:①The levels of serum and urinary NGAL are significantly elevated in SLE patients, especially in patients with nephritis.②The levels of urinary NGAL are positively correlated with renal SLEDAI scores. There was no correlation between serum NGAL and the SLEDAI.③Urinary NGAL levels had a strong and significant correlation with Upro:Ucre values. The results suggest that NGAL may play a role in SLE patients with nephritis.