CBC-Derived Inflammatory Indices and Myocardial Injury Severity at Presentation in Acute Myocardial Infarction:...

Background: Early assessment of myocardial injury severity at presentation remains challenging in acute myocardial infarction (AMI). Complete blood count (CBC)-derived inflammatory indices may provide accessible adjunctive biomarkers reflecting early systemic inflammatory activation associated with myocardial injury. This study evaluated the association and discriminative performance of CBC-derived inflammatory indices for presentation-time myocardial injury severity. Methods: This retrospective study included 252 patients with AMI. CBC-derived inflammatory indices, including the neutrophil-to-lymphocyte ratio (NLR) and neutrophil-to-lymphocyte × platelet ratio (NLPR), were calculated from blood samples obtained at presentation (0 h). Correlation analysis, multivariable linear regression, logistic regression, incremental model analysis, and receiver operating characteristic (ROC) analysis were performed to assess associations with high-sensitivity Troponin T (hs-Troponin T) levels and high myocardial injury, defined as the highest hs-Troponin T tertile. Results: Both log NLR and log NLPR showed significant positive correlations with log hs-Troponin T (ρ = 0.422 and 0.396, respectively; p < 0.001). In multivariable linear regression adjusted for clinical variables and AMI subtype, log NLR (B = 0.88, p < 0.001) and log NLPR (B =0.77, p < 0.001) remained independently associated with log hs-Troponin T. Incremental model analysis demonstrated significant increases in explanatory performance after addition of log NLR (ΔR² = 0.137) and log NLPR (ΔR² = 0.121, p < 0.001). In logistic regression, log NLR (adjusted OR 2.77, 95% CI 1.65-4.66) and log NLPR (adjusted OR 2.46, 95% CI 1.53-3.95) were independently associated with high myocardial injury. ROC analysis demonstrated modest improvement in discrimination after incorporation of inflammatory indices, with AUC increasing from 0.709 for the baseline clinical model to 0.778 with log NLR and 0.770 with log NLPR. Supplementary reclassification analyses demonstrated improved classification performance. Conclusions: CBC-derived inflammatory indices, particularly NLR and NLPR, were independently associated with presentation-time myocardial injury severity in patients with AMI, even after adjustment for AMI subtype. Although improvements in ROC-based discrimination were modest, supplementary reclassification analyses suggested incremental value beyond conventional clinical variables and AMI subtype. These findings support the potential utility of CBC-derived inflammatory indices for early assessment of myocardial injury during AMI presentation.