Red blood cell count and cystatin C as the specific biomarkers for diabetic retinopathy from diabetes mellitus: a case–control study

Diabetic retinopathy (DR) is a common microvascular complication of diabetes mellitus (DM). However, the blood physiological indicators for this eye disease are less reported. Here, we systemically investigated healthy controls, DR patients and DM patients from 2014 to 2022 in Sichuan Provincial People's Hospital (Chengdu, China). We found the leukocyte count, urea, and direct bilirubin in the DR patients were significantly increased (P < 0.001) compared with the controls. The ratios of aspartate aminotransferase/alanine transaminase, total bilirubin, indirect bilirubin, and red cell distribution width were lower in the DR patients than in the controls (P < 0.001). Notably, Red blood cell count (mean [SD] = 4.54 [0.67] 10E12/L, OR = 0.75) was significantly decreased (P < 0.001), and cystatin C level (mean [SD] = 1.42 [1.13] mg/L, OR = 1.90) was significantly increased in the DR patients compared with the controls (P < 0.001). However, these two indicators were not significantly different between the DM patients and the controls (P = 0.87 and P = 0.14, respectively). Our results showed that red blood cell count and cystatin C are specific biomarkers for DR patients.