Current systemic predictors for diabetic retinopathy (DR) – such as HbA1c, blood pressure, and lipid profiles – explain only part of the risk, limiting their utility for early, individualized intervention. Now, a cross‑sectional TVST study of 1,078 hospitalized T2DM patients has sought to evaluate C‑peptide (CP)–related indices, focusing on the postprandial C‑peptide to glucose ratio (PCGR), as predictors of DR and vision‑threatening DR (VTDR).
In the Beijing-based study, participants underwent standardized systemic and ophthalmic evaluations, including ultra‑widefield fundus photography and OCT. CP indices – fasting CP (FCP), postprandial CP (PCP), delta CP, fasting and postprandial CP/glucose ratios (FCGR, PCGR), HOMA‑B, and HOMA‑IR – were compared across DR stages (no DR, mild/moderate nonproliferative DR, VTDR). Logistic regression models adjusted for age, sex, diabetes duration, HbA1c, SBP, and insulin use.
The results showed that PCGR had the strongest inverse association with both DR and VTDR, reinforcing the link between impaired β‑cell function – rather than insulin resistance – and DR development in T2DM.
In terms of clinical implications, PCGR is inexpensive, easily derived from routine postprandial CP and glucose testing, and could help identify high‑risk patients for closer retinal monitoring and earlier intervention. This could position PCGR as a promising, accessible biomarker for DR risk stratification in T2DM, with particular value in predicting progression to VTDR beyond conventional risk factors.
