AIM: To explore the relationship between serum uric acid(SUA)and cystatin C(CysC)levels with diabetic retinopathy(DR).

METHODS: A prospective study.A total of 53 non-DR patients with type 2 diabetes mellitus(T2DM; T2DM group)and 83 patients with DR admitted to the hospital between May 2019 and May 2021 were enrolled. In DR patients, there were 47 cases with non-proliferative diabetic retinopathy(NPDR)in NPDR group and 36 cases with proliferative diabetic retinopathy(PDR)in PDR group. A total of 48 healthy people in physical examination center during the same period were enrolled as control group. The serological indexes of all subjects were compared. SUA level was detected by urate oxidase method. The level of serum CysC was detected by immunoturbidimetry. The correlation between serum SUA, CysC and the other serological indexes was analyzed by Spearman. The influencing factors of serum SUA and CysC were analyzed by multivariate linear stepwise regression method. The predictive efficiency of serum SUA and CysC for DR was analyzed by receiver operating characteristic(ROC)curves.

RESULTS: The body mass index(BMI)and systolic blood pressure(SBP)in T2DM, NPDR and PDR group were significantly higher than those in control group(all P<0.05). SBP in PDR group was significantly higher than that in T2DM and NPDR group(all P<0.05). The course of diabetes mellitus in NPDR and PDR group was significantly longer than that in T2DM group(all P<0.05), and it was significantly higher in PDR group than in NPDR group(P<0.05). The levels of fasting plasma glucose(FPG), hemoglobin Alc(HbA1c), SUA and CysC in control group, T2DM group, NPDR group and PDR group were gradually increased(all P<0.001). The levels of low-density lipoprotein cholesterol(LDL-C)and triglyceride(TG)in PDR group were significantly higher than those in control group(all P<0.05), while level of high-density lipoprotein cholesterol(HDL-C)was significantly lower than that in control group(P<0.05). The levels of serum SUA were positively correlated with FPG, HbA1c, total cholesterol(TC)and TG levels(r_s=0.564, 0.631, 0.513, 0.408, P<0.001), but they were not correlated with HDL-C or LDL-C(r_s=-0.061, 0.035, P>0.05). The levels of serum CysC were positively correlated with FPG, HbA1c, TC and TG levels(r_s=0.524, 0.692, 0.395, 0.435, P<0.001), but they were not correlated with HDL-C or LDL-C(r_s=-0.012, 0.049, P>0.05). FPG, HbA1c, TC and TG were influencing factors of serum SUA and CysC levels(P<0.001). The area under the curve(AUC)in the combined detection of SUA and CysC(0.892, 95%CI: 0.840-0.944, sensitivity:71.1%, specificity: 94.3%), was significantly greater than that of AUC \〖SUA(0.807, 95%CI: 0.735-0.879, sensitivity: 69.9%, specificity: 75.5%)and CysC(0.763, 95%CI: 0.684-0.841, sensitivity: 69.9%, specificity: 75.5%)\〗 alone(all P<0.05).

CONCLUSION: The levels of serum SUA and CysC gradually increase with the aggravation of DR. The combined detection of serum SUA and CysC can improve the diagnostic and predictive efficiency for DR.