A correlation analysis between serum cystatin C with Lee's grading and Oxford classification of IgA nephropathy

Objective To analyze the correlation of serum cystatin C (Cys C) with Lee's grading and Oxford classification of IgA nephropathy in order to provide the basis for evaluating the severity of the disease. Methods A total of 191 patients with primary IgA nephropathy diagnosed by renal biopsy in Longhua Hospital between Jan. 2013 and Jan. 2018 were enrolled into the research. According to Lee's grading standard and interstitial fibrosis and tubuloatrophy (T) grading standard of Oxford classification, the patients were divided into 3 subgroups (mild, moderate and severe) separately and were also divided into 2 subgroups according to crescents (C) grading standard of Oxford classification. The levels of serum Cys C, serum albumin (Alb), serum creatinine (SCr), blood urea nitrogen (BUN), uric acid (UA), 24-h urinary protein and 24-h urinary micro albumin were determined, the estimated glomerular filtration rate (eGFR) was calculated by chronic kidney disease-epidemiology collaboration (CKD-EPI) equation and then the correlation of Cys C with Lee's grading and Oxford classification was analyzed. Results With the aggravating degrees of renal pathological lesions, the levels of Cys C, SCr and BUN were gradually increased while eGFR was gradually decreased in Lee's and T subgroups (P<0.01). The above correlations were also proved by multiple linear regression analysis. Spearman correlation analysis showed that Cys C was positively correlated with Lee's grading and T grading of Oxford classification (r=0.768, r=0.624, P<0.01, but negatively with eGFR (r=-0.804, P<0.01). The levels of serum Cys C was higher in crescent group than in non-crescent group (P<0.01). Spearman correlation analysis also showed Cys C was positively correlated with C grading of Oxford classification (r=0.181, P<0.01), and multiple linear regression analysis did not show a strong correlation between the two. Therefore, this correlation still needed to be further confirmed. Conclusions Cys C can serve as a sensitive biomarker for reflecting the pathological injury grade, especially the degree of interstitial tubule injury in early stage of IgA nephropathy.