Clinical Significance Of Urinary Ferritin/creatinine Ratio And Urinary Transferrin/creatinine Ratio In The Evaluation Of Disease Activity Of Systemic Lupus Erythematosus

Objective:Recent studies reported an increase of ferritin and transferrin in systemic lupus erythematosus(SLE).This study aims to investigate the clinical significance of urinary ferritin/creatinine ratio(UFCR)and urinary transferrin/creatinine ratio(UTCR)in the diagnosis and evaluation of SLE disease activity.Methods:Samples from 62 SLE patients [35 with lupus nephritis(LN)and 27 without LN] and 19 healthy controls were evaluated.The amount of urinary ferritin and urinary transferrin were measured by enzyme-linked immunosorbent assay(ELISA)and normalized by the amount of urinary creatinine to obtain the UFCR and UTCR.The relationship between UFCR,UTCR and inflammatory markers and laboratory indicators was also investigated by correlation analysis.Results:UFCR level in active SLE patients is significantly higher than in inactive SLE patients {17.51 mg/?mol [4.88,36.14] vs.2.36 mg/?mol [0.75,12.71],P=0.001} or healthy controls {0.31mg/?mol [0.25,0.38],P<0.001}.In addition,UFCR level in active LN patients is significantly higher than in inactive LN patients {27.48 mg/?mol [7.89,65.20] vs.9.8 mg/?mol [2.0,28.09],P=0.021} or nLN patients {2.01 mg/?mol [0.69,2.75],P<0.001} or healthy controls(P<0.001).UFCR level is positively correlated with Systemic Lupus Erythematosus Disease Activity Index(SLEDAI)(r=0.542,P =0.000),ESR(r=0.498,P =0.000),serum ferritin(r=0.608,P =0.000),but negatively correlated with the levels of complement C3(r=-0.412,P =0.001),complement C4(r=-0.336,P =0.008).Further more,UFCR level is closely related to kidney indicators such as 24 h urine protein quantitation(r=0.732,P =0.000),serum creatinine(r=0.319,P =0.011),serum cystatin C(r=0.653,P =0.000),serum urea(r=0.308,P =0.015)and glomerular filtration rate(GFR)(r=-0.424,P =0.001).UTCR in the SLE patients with LN was significantly higher than that in the patients without LN {61.80[31.40,106.00]×10-5ng/ng vs.31.52[7.45,53.88]×10-5 ng/ng,P=0.006 ] or healthy controls{4.07[0.31,7.37]×10-5 ng/ng}(P =0.000).UTCR was positively correlated with SLEDAI score(r=0.454,P =0.001),ESR(r=0.35,P =0.005),CRP(r=0.301,P =0.018),24 h urinary protein quantification(r=0.471,P =0.000)and serum cystatin C(r=0.462,P =0.000),but negatively correlated with C3(r=-0.303,P =0.016).Conclusion:UFCR and UTCR level is elevated significantly both in SLE and LN patients and correlates with disease activity,suggesting its utility as a potential biomarker for the diagnosis of LN in SLE patients,and can also be used to assess SLE and LN disease activity.In addition,the increase in UFCR level is closely related to renal involvement,indicating that the level of UFCR can reflect the severity of kidney injury in SLE patients.