Supplementary Material for: The retinal blood flow density is related to the pathological severity of diabetic kidney disease.

Introduction: This study aimed to investigate the correlation between fundus blood flow parameters and the severity of pathological biopsy in patients with diabetic kidney disease (DKD).
Methods: Data of patients with type 2 diabetes mellitus who completed renal pathology biopsies and optical coherence tomography angiography (OCTA) examinations, including renal function, 24-h urine protein quantification, and macular flow imaging, were collected. DKD pathology biopsies were graded as stages 1–4, and differences and correlations of the parameters were compared between groups. The grading was transformed into early (stage 1) and late (stages 2–4), and regression analyses were conducted to develop a model, draw a nomogram, and test efficacy.
Results: This study included 157 eyes from 157 individuals in total. Urinary microalbumin and to urinary creatinine ratio (mALB/NCR) increased with pathological grading, whereas while glomerular filtration rate was decreased (p < 0.01). Corresponding retinal blood flow in superficial, deep, and full paracentral rings was decreased, which correlated with pathological grading (p < 0.01), with the highest blood flow density in the whole layer (r2 = –0.707). Meaningfully, in the early DKD model (area under the curve =0.929 (0.889–0.970), p < 0.01), whole-layer blood flow density, mALB/NCR, and diabetes duration were statistically significant.
Conclusions: The decrease in macular retinal blood flow density detected by OCTA is closely associated with the increase in pathological grading of DKD and can be used as a noninvasive parameter for monitoring early changes in DKD.

引言：本研究旨在探讨糖尿病肾病（diabetic kidney disease, DKD）患者的眼底血流参数与病理活检严重程度的相关性。
方法：收集完成肾脏病理活检及光学相干断层扫描血管成像（optical coherence tomography angiography, OCTA）检查的2型糖尿病患者临床数据，涵盖肾功能、24小时尿蛋白定量及黄斑部血流成像资料。将DKD病理活检结果划分为1~4期，对比各组参数的差异与相关性。进一步将分期重新归类为早期（1期）与晚期（2~4期），开展回归分析以构建预测模型、绘制列线图并验证其效能。
结果：本研究共纳入157名受试者的157只患眼。尿微量白蛋白与尿肌酐比值（mALB/NCR）随病理分期升高而升高，而肾小球滤过率则随之降低（P<0.01）。旁中心凹区浅层、深层及全层视网膜血流密度均呈下降趋势，且与病理分期显著相关（P<0.01），其中全层血流密度的相关性最高（r²=-0.707）。尤为重要的是，早期DKD预测模型的曲线下面积为0.929（0.889~0.970），P<0.01，全层血流密度、mALB/NCR及糖尿病病程均具有统计学意义。
结论：光学相干断层扫描血管成像（OCTA）检测得到的黄斑部视网膜血流密度降低，与DKD病理分期升高密切相关，可作为监测DKD早期病变的无创性评估参数。