PDR remains a leading cause of irreversible vision loss in individuals with T2DM. A retrospective analysis published in Diabetes Metabolic Syndrome and Obesity evaluated whether Hb and DBil levels can predict PDR in routine clinical care.

The study included 1,496 individuals with diabetic retinopathy treated at the South District of the First People’s Hospital of Hefei. Logistic regression, correlation analysis, restricted cubic spline modeling, and Mendelian randomization assessments were performed.

Each unit increase in Hb was associated with a 4.4 percent reduction in PDR risk, while each unit increase in DBil was associated with a 29.1% reduction. Risk decreased as hemoglobin rose up to approximately 133 g/L and plateaued beyond that threshold. A similar non-linear trend for direct bilirubin was observed with a turning point at 2.67 µmol/L.

A combined diagnostic model that included both biomarkers achieved an area under the curve (AUC) of 0.742, with sensitivity of 54.5% and specificity of 86.5%. Subgroup analyses revealed higher PDR prevalence with worsening anemia. Mendelian randomization supported a possible association between genetically predicted anemia and elevated PDR risk (odds ratio 1.06, 95 percent confidence interval 1.003–1.12).

These findings suggest that lower hemoglobin and direct bilirubin levels may help identify increased PDR risk. Confirmation in prospective, population-based studies is needed before clinical application.