Evaluating Platelet-to-Lymphocyte Ratio and Systemic Immune-Inflammation Index as Distinctive Biomarkers in Type 2 Diabetes Mellitus Patients With and Without Proteinuria: A Retrospective Study

Background Diabetic kidney disease (DKD), a leading cause of chronic kidney disease (CKD) and end-stage renal disease globally, is driven by metabolic and inflammatory processes. Systemic immune-inflammation index (SII) and platelet-to-lymphocyte ratio (PLR) are emerging biomarkers that integrate inflammatory and hematological components, potentially reflecting severity of renal dysfunction. Methods This retrospective study analyzed 160 patients from January 2023 to December 2023 with type 2 diabetes mellitus (T2DM), equally divided into proteinuria and non-proteinuria groups. SII and PLR levels were compared between groups, and their correlations with urine albumin-to-creatinine ratio (ACR) and protein levels were evaluated using statistical measures, including Pearson's correlation and regression analyses. Results SII and PLR levels were significantly higher in the proteinuria group (SII: 1,305,266 vs. 456,957.4 cells per microliter; PLR: 252.09 vs. 99.74, p<0.001 for both). SII and PLR exhibited strong positive correlations with urine ACR (SII: r=0.8537, PLR: r=0.8362) and protein levels (SII: r=0.834, PLR: r=0.841, p<0.01 for both). Regression analysis revealed a complex, nonlinear association between these biomarkers and increasing proteinuria severity, indicating their dynamic behavior across protein categories. HbA1c demonstrated a parabolic relationship with urine ACR, with progressively larger effects at higher levels, highlighting its role in worsening renal dysfunction. Conclusion SII and PLR are robust markers of inflammation and renal injury in T2DM, showing strong associations with proteinuria and urine ACR. These indices, alongside HbA1c, may aid in early detection and monitoring of DKD progression, particularly in resource-constrained settings.