Inflammatory Prognostic Index: A Novel Predictor of In-Stent Restenosis Following Drug-Eluting Stent–Percutaneous Coronary Intervention

<b>Background:</b> The Inflammatory Prognostic Index (IPI) is a novel biomarker integrating C-reactive protein (CRP), albumin, and white blood cell-derived ratios, reflecting systemic inflammation and nutritional status. Inflammation is central to in-stent restenosis (ISR). This study investigated the prognostic value of IPI in predicting ISR after drug-eluting stent (DES) implantation. <b>Methods:</b> We retrospectively analyzed 571 patients who underwent DES implantation and follow-up angiography at a median of 12 months (IQR 12-24) for recurrent angina or ischemia. Patients were grouped as ISR (+) (<i>n</i> = 218) and ISR (-) (<i>n</i> = 353). IPI was calculated as (CRP × neutrophil-to-lymphocyte ratio)/albumin. Logistic regression and ROC analyses assessed the predictive role of IPI. <b>Results:</b> ISR occurred in 38.1% of patients. The ISR (+) group showed a higher prevalence of hypertension and active smoking, as well as higher CRP, glucose, and neutrophil levels, but lower albumin and lymphocytes (all <i>p</i> < 0.05). Elevated IPI independently predicted ISR (OR = 2.90; 95% CI = 2.35-3.57; <i>p</i> < 0.001). ROC analysis showed an optimal cutoff of 1.275 (sensitivity 84.4%, specificity 74.5%). <b>Conclusions:</b> IPI, derived from routine laboratory tests, independently predicts ISR after DES implantation and may serve as a simple, inexpensive biomarker for coronary artery disease risk stratification.