Early Identification of ST-Segment Elevation Myocardial Infarction (STEMI) at Presentation: Comparative Diagnostic Performance of CBC-Derived Inflammatory Indices and High-Sensitivity Troponin T

Background/Objectives: Early identification of ST-segment elevation myocardial infarction (STEMI) at first medical contact remains challenging, as high-sensitivity troponin T may be insufficiently sensitive during the initial phase of myocardial injury. Readily available complete blood count (CBC)-derived inflammatory indices may provide complementary early diagnostic signals. This study aimed to evaluate whether baseline CBC-derived inflammatory indices differ between STEMI and NSTEMI and whether they provide adjunctive discriminatory information at presentation (0 h) in patients with acute coronary syndrome (ACS). Methods: A 12-lead electrocardiogram (ECG), high-sensitivity troponin T, and CBC were obtained at presentation from 252 patients with ACS (195 STEMI and 57 NSTEMI). Diagnostic performance was evaluated using receiver operating characteristic (ROC) curve analysis and 2 × 2 contingency tables to determine the area under the curve (AUC), sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and likelihood ratios. Results: High-sensitivity troponin T demonstrated the highest specificity (84.44%) and PPV (92.93%), supporting its role as a confirmatory biomarker; however, its low sensitivity (50.83%) and NPV (29.92%) may reduce its utility during early assessment. In contrast, WBC and neutrophil counts demonstrated relatively favorable discriminatory performance at presentation (AUC > 0.72; Youden’s index > 0.40). Among composite indices, NLPR demonstrated the highest sensitivity (88.66%) and NPV (53.19%), along with the lowest negative likelihood ratio (0.25), suggesting potential adjunctive value during early assessment. NLR, SII, SIRI, and adjusted NLR showed moderate performance, with aNLR providing a balanced sensitivity (67.01%) and specificity (74.55%). Conclusions: CBC-derived inflammatory indices, particularly neutrophil-based markers such as NLPR, may provide adjunctive discriminatory information during the early assessment of patients with ACS, particularly at first medical contact when baseline hs-Troponin T sensitivity may still be limited.