Diagnostic Performance of Complete Blood Count Derived Indices for Acute Coronary Syndrome in Emergency Department Patients With Acute Chest Pain: A Single‐Center Retrospective Diagnostic Accuracy Study

ABSTRACT Background and Aims Acute coronary syndrome (ACS), as one of the cardiovascular diseases, plays a significant role in patient mortality. Although appropriate diagnostic methods have been introduced for ACS, it still remains a challenge for physicians. Therefore, utilizing additional markers and ratios for the diagnosis of ACS can be beneficial. Hence, our study was conducted with the aim of evaluating the diagnostic value of indices and ratios derived from the complete blood count (CBC) test. Methods In this retrospective diagnostic accuracy study, 360 patients presenting with acute chest pain to the emergency department of Allameh Bohlool Hospital were evaluated. Patients were classified into ACS (n = 167) and Non‐ACS (n = 193) groups based on the final clinical diagnosis. CBC‐derived parameters, including leukocyte count, neutrophil count, monocyte count, platelet count, mean platelet volume (MPV), neutrophil‐to‐lymphocyte ratio (NLR), monocyte‐to‐lymphocyte ratio (MLR), and platelet‐to‐lymphocyte ratio (PLR), were assessed. Diagnostic performance was evaluated using receiver operating characteristic (ROC) curve analysis. Multivariable logistic regression models were developed to determine independent associations and assess the incremental diagnostic value of CBC‐derived markers beyond clinical variables. Results Patients with ACS had significantly higher leukocyte count, neutrophil count, monocyte count, MPV, NLR, and MLR levels compared with Non‐ACS patients (all p < 0.01). Among individual biomarkers, neutrophil count demonstrated the highest diagnostic performance (AUC = 0.720; 95% CI, 0.668–0.772), followed by leukocyte count (AUC = 0.704; 95% CI, 0.651–0.758) and NLR (AUC = 0.669; 95% CI, 0.613–0.725). After adjustment for clinical variables, leukocyte count (adjusted OR = 1.64; 95% CI, 1.41–1.91; p < 0.001) and neutrophil count (adjusted OR = 1.68; 95% CI, 1.42–1.99; p < 0.001) remained independently associated with ACS. Addition of leukocyte count to the clinical model significantly improved discrimination (AUC increased from 0.787 to 0.850; ΔAUC = 0.063; DeLong p < 0.001). Conclusion In this study, selected CBC‐derived parameters, particularly neutrophil count, leukocyte count, and NLR, showed statistically significant but limited discriminatory ability for ACS. These indices may be considered adjunctive inflammatory markers, but their diagnostic performance is insufficient for use as stand‐alone tests and should be interpreted alongside clinical assessment, ECG, and cardiac troponin testing.