Association of estimated glomerular filtration rate with proliferative diabetic retinopathy: a systematic review and meta-analysis.

Background: Proliferative diabetic retinopathy (PDR) is a serious vision-threatening complication of diabetes. Chronic kidney disease (CKD), measured by estimated glomerular filtration rate (eGFR), shares similar pathophysiological mechanisms with diabetic retinopathy, including inflammation, oxidative stress, and vascular dysfunction. However, the strength of the association between eGFR and PDR remains unclear. This review evaluates the association between reduced eGFR and the risk of PDR in individuals with diabetes.

Methods: A comprehensive literature search was conducted in PubMed, Embase, and Web of Science, from inception to October 2024. Observational studies reporting both eGFR values and PDR status were included. Study quality was assessed using the Newcastle-Ottawa Scale. Pooled standardized mean differences (SMD) were calculated using a fixed-effects model when heterogeneity was low (I² ≤ 50%). Subgroup analyses based on eGFR estimation method Modification of Diet in Renal Disease (MDRD) and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI), sensitivity analyses, and meta-regression for diabetes duration and HbA1c were conducted. Publication bias was evaluated using funnel plots and Egger's test.

Results: A total of 11 studies were included, comprising 602 patients with PDR and 5,475 individuals without diabetic retinopathy. The pooled SMD for eGFR between PDR and non-PDR groups was - 0.43 (95% CI - 0.52 to - 0.34; P < 0.0001), indicating significantly lower eGFR in PDR patients. Heterogeneity was moderate (I² = 42.3%). Subgroup analysis showed an SMD of - 0.58 (95% CI - 1.02 to - 0.14; I² = 0%) using the MDRD formula and - 0.43 (95% CI - 0.58 to - 0.28; I² = 80.4%) with the CKD-EPI formula. Meta-regression revealed a significant negative association between diabetes duration and PDR proportion (P = 0.0155), but no association with HbA1c (P = 0.7798). The prediction interval ranged from - 0.53 to - 0.33. Funnel plot asymmetry suggested potential publication bias (P < 0.05).

Conclusions: This systematic review and meta-analysis found a significant association between reduced eGFR and PDR in patients with diabetes, with consistent findings across studies and eGFR estimation methods. Though heterogeneity suggests caution in interpretation. Additional prospective using standardized methodologies are needed to clarify causality and enhance risk prediction.