High-Sensitivity C-Reactive Protein and its Association with Diabetic Retinopathy: A Cross-sectional Study

Chronic low-grade inflammation is implicated in diabetic microvascular complications, but the relationship between circulating high-sensitivity C-reactive protein (hs-CRP) and diabetic retinopathy (DR) in type 2 diabetes mellitus (T2DM) remains incompletely defined. We evaluated whether plasma hs-CRP levels are independently associated with DR presence and severity in a cohort of T2DM patients.

In this analytical cross-sectional study, 149 T2DM patients referring to endocrinology and ophthalmology clinics at Babol University of Medical Sciences (April 2022-June 2023) were categorized into no DR (n=50), non-proliferative DR (NPDR; n=49), and proliferative DR (PDR; n=50) groups. Comprehensive ophthalmic examination classified DR stage. We measured hs-CRP (low: 0-1 mg/L, moderate: 1-3 mg/mL, high:>3 mg/mL), HbA1c, fasting blood sugar (FBS), and total cholesterol in fasting blood samples. Statistical analysis was performed with SPSS v.22.

Mean hs-CRP concentrations rose progressively with DR severity: 2.71±1.14 mg/L (no DR), 4.89±5.31 mg/L (NPDR), and 10.60±9.24 mg/L (PDR; P=0.023). After adjusting for age, sex, diabetes duration, HbA1c, BMI, hypertension, smoking, cholesterol, and treatment, each 1 mg/L increase in hs-CRP was associated with 1.40-fold higher odds of DR (OR 1.40; 95% CI 1.08-1.94; P=0.011). Other independent predictors included longer diabetes duration (OR 1.19 per year; 95% CI 1.10-1.29; P<0.001), higher HbA1c (OR 1.62 per %; 95% CI 1.06-2.48; P=0.023), and female sex (OR 3.25; 95% CI 1.11-9.52; P=0.031).

High hs-CRP levels correlate with DR severity in T2DM, highlighting inflammation's role and potential for early detection strategies.