Significance Of SCys-C In Renal Impairment Of Primary Sj(?)gren’s Syndrome

Objective:To investigate the level of serum cystatin C（SCys-C）in patients with primary Sj（?）gren’s syndrome（pSS）,analyze the correlation between SCys-C and pSS renal impairment,and evaluate the clinical application value of SCys-C for pSS renal impairment.Methods:A total of 118 patients with primary Sj（?）gren’s syndrome diagnosed in the Department of Rheumatology and Immunology of the Second Hospital of Hebei Medical University from January 2014 to January2021 were retrospectively analyzed and used as the study group.The study group was further divided into renal impairment group（n=54）and non-renal impairment group（n=64）according to the presence or absence of renal impairment,and then 74 healthy subjects were selected as the control group.The differences in laboratory parameters such as SCys-C,serumβ2microglobulin（Sβ2-MG）,serum creatinine（SCr）,blood urea nitrogen（BUN）,blood uric acid（SUA）,urine PH(U_PH)and urine specific gravity(U_SG)between the groups were compared.According to whether the disease course was more than 3 years,the study group was further divided into the short-duration group（n=72）and the long-duration group（n=46）,and the differences in laboratory parameters such as SCys-C,Sβ2-MG,SCr,BUN,SUA,U_PH and U_SG between the two groups were analyzed.The correlation between SCys-C levels and laboratory parameters such as SCys-C,Sβ2-MG,SCr,SUA,U_PHand U_SG was analyzed in pSS patients.Binary logistic regression was applied to analyze the risk factors for renal impairment in pSS.Receiver operating characteristic curve（ROC Curve）was drawn,and the cut-off value corresponding to the maximum Youden Index（YI）was calculated to evaluate the efficacy of SCys-C in predicting renal impairment in pSS.Results:1.The levels of SCys-C,Sβ2-MG,SCr,BUN and U_PH in study group were higher than those in control group,and the level of U_SG was lower than that in control group,and the differences had statistical significance（P<0.05for all）.2.The levels of SCys-C,Sβ2-MG,SCr,BUN and U_PH in the pSS renal impairment group were higher than those in the pSS non-renal impairment group,and the levels of SUA and U_SG were lower than those in the pSS non-renal impairment group,and the differences were statistically significant（P<0.05 for all）.3.There were no statistically significant differences in the levels of SCys-C,Sβ2-MG,SCr,BUN,U_PH,U_SG,C3,C4,Ig G,Anti-SSA and Anti-SSB between the short-duration group and the long-duration group（P>0.05 for all）.4.SCys-C levels were positively correlated with Sβ2-MG levels（r=0.548,P=0.000）,SCr levels（r=0.668,P=0.000）,BUN（r=0.451,P=0.000）,U_PH（r=0.491,P=0.000）,Ig G levels（r=0.209,P=0.023）,were negatively correlated with e GFR（r=-0.591,P=0.000）,U_SG（r=-0.371,P=0.000）.5.The results after binary logistic regression analysis showed that SCys-C>1.30mg/L（OR=63.489,P=0.000）,U_PH>6.5（OR=12.969,P=0.001）and U_SG<1.011（OR=4.773,P=0.038）were independent risk factors for renal impairment in pSS.6.The plotted ROC curve showed that the area under the curve（AUC）of SCys-C was 0.959（P=0.000）,the cut-off value of SCys-C level at YI_MAXwas 1.37 mg/L,and the sensitivity of this value as a predictor of renal impairment in patients with pSS was 85.2%and the specificity was 95.3%;the AUC of SCr was 0.914（P=0.000）,the cut-off value of SCr level at YI_MAX was58.30μmol/L,and the sensitivity of this value as a predictor of renal impairment in patients with pSS was 94.4%and the specificity was 79.7%;the AUC of BUN was 0.768（P=0.000）,the cut-off value of BUN level at YI_MAXwas 5.55μmol/L,and the sensitivity of this value as a predictor of renal impairment in patients with pSS was 59.3%and the specificity was 82.8%;the AUC ofβ2-MG was 0.743（P=0.000）,the cut-off value of Sβ2-MG level at YI_MAX was 2.85mg/L,and the sensitivity of this value as a predictor of renal impairment in patients with pSS was 47.5%and the specificity was 85.1%;AUC of SUA was 0.379（P=0.007）;AUC of e GFR was 0.107（P=0.000）.Conclusions:1.SCys-C levels in pSS patients were significantly increased compared with healthy individuals,and were positively correlated with Sβ2-MG,SCr and BUN.2.SCys-C>1.30 mg/L is an independent risk factor for predicting renal impairment in pSS.3.SCys-C can be used as an indicator to detect renal impairment in pSS,and its efficacy is superior to that of Sβ2-MG,SCr and BUN.