Novel Systemic Marker Identifies Diabetes Patients at High Risk of DR

A new study found that, compared with insulin resistance, parameters indicative of β-cell function—specifically, postprandial C-peptide to glucose ratio (PCGR)—were more closely related to DR independent of diabetes duration than HbA1c or other confounding factors. This chart from the study show the AUC curves for PCGR (red line) vs. HbA1c (blue line). Monitoring this systemic marker could help identify patients with type 2 diabetes who require more frequent fundus screenings. Photo: Zheng Z, et al. Transl Vis Sci Technol. 2025;14(7):27. Click image to enlarge.  Fasting blood glucose levels are a mainstay of diabetes management, but a team of researchers from China argue that “postprandial” (i.e., after eating) testing also offers unique insights into disease status, especially as it relates to risk of  diabetic retinopathy (DR). While routine fundus screening and measurements are useful for detecting active lesions, few parameters have been shown to accurately predict DR risk in patients with type 2 diabetes mellitus. In a new study, researchers identified one promising systemic marker—postprandial C-peptide to glucose ratio—that could help distinguish patients more likely to develop this complication, particularly vision-threatening DR. The cross-sectional observational study, conducted in Beijing, included 1,078 hospitalized patients aged 30 to 80 years with type 2 diabetes. After screening for eligibility, data collected included fasting and postprandial C-peptide levels, glucose ratios and various parameters indicating β-cell function and insulin resistance. Of the study population, 52.9% were deemed to have no DR, 34.6% had mild to moderate nonproliferative DR (NPDR) and 12.4% experienced vision-threatening DR.The study found that the postprandial C-peptide to glucose ratio was a stronger predictor of DR severity compared to traditional markers like fasting C-peptide levels. Notably, the odds ratio for the presence of mild/moderate NPDR for each standard deviation increase in postprandial C-peptide to glucose ratio was 0.44, while for vision-threatening DR it was even more pronounced at 0.09. Receiver operating characteristic analysis further supported this finding, illustrating an area under the curve of 0.76 for DR and 0.83 for vision-threatening DR, which indicated a robust capacity of the postprandial C-peptide to glucose ratio to differentiate between the presence and absence of DR.“We found that, compared with insulin resistance, the parameters indicative of β-cell function were more related to DR independent of duration of diabetes, HbA1c and some other confounding factors,” the researchers wrote in their paper for Translational Vision Science & Technology. “More importantly,” they continued, “postprandial C-peptide to glucose ratio showed the most significant association with the occurrence and progression of DR, which could act as a promising systemic marker in predicting patients at a high risk of developing DR,” especially vision-threatening presentations.The researchers concluded that monitoring this easily obtainable clinical marker could help with individualized management and may identify patients who “require more frequent fundus follow-ups and more intensive hypoglycemic therapy.”Click here for the journal source. Zheng Z, Liu N, Zhang Y, et al. Postprandial C-peptide to glucose ratio as a promising systemic marker of diabetic retinopathy in type 2 diabetes. Transl Vis Sci Technol. 2025;14(7):27.  This article was developed by the editorial staff in conjunction with experts in the field. In the process, AI may have been among the editorial tools used to meet the goals of human editors, who approved all content.