Value of Serum Retinol-Binding Protein, Lipoprotein A and Inflammatory Nutritional Indexes and their Interactions in Predicting Acute Kidney Injury after Coronary Angiography

Background: Contrast-induced acute kidney injury (CI-AKI) is a serious condition that can arise after undergoing coronary angiography (CAG). This complication is primarily caused by the toxic impact of contrast agents on the kidneys, along with oxidative stress and inflammatory responses. Identifying reliable biomarkers for early prediction remains essential due to the limited accuracy of existing clinical risk scores. Methods: This retrospective case-control study included 365 patients undergoing CAG between December 2021 and December 2023. Patients were categorized into non-AKI (n = 320) and AKI (n = 45) groups based on post-procedural renal function. Biomarkers including serum retinol-binding protein (RBP), lipoprotein A (Lp(a)), interleukin-6 (IL-6), and nutritional markers were measured. Baseline demographics, lipid profiles, and procedure details were recorded. Results: Baseline characteristics revealed no significant differences between groups in terms of age, BMI, gender, and prevalence of hypertension or diabetes mellitus. Notably, RBP (41.83 ± 10.22 mg/L vs. 32.45 ± 8.76 mg/L, p < 0.001), Lp(a) (42.35 ± 13.87 mg/dL vs. 35.76 ± 11.54 mg/dL, p < 0.001), and IL-6 (6.23 ± 2.14 pg/mL vs. 4.87 ± 1.59 pg/mL, p < 0.001) levels were significantly higher in the AKI group. Total protein levels were significantly lower in the AKI group (6.88 ± 0.62 g/dL vs. 7.12 ± 0.54 g/dL, p = 0.006). Multivariate logistic regression identified RBP (OR 1.118, 95% CI 1.072–1.166, p < 0.001), Lp(a) (OR 1.047, 95% CI 1.014–1.080, p = 0.005), and IL-6 (OR 1.710, 95% CI 1.355–2.157, p < 0.001) as independent predictors of AKI, while higher total protein levels were protective (OR 0.497, 95% CI 0.257–0.960, p = 0.037). Conclusion: Serum RBP, Lp(a), IL-6, and total protein levels are valuable biomarkers for predicting CI-AKI after CAG. Elevated RBP, Lp(a), and IL-6 indicate higher risk, while higher total protein suggests protective effects.