A-028 Comparison of the Cardiac Troponin I-T-C complex and cTnI and cTnT in Distinguishing Myocardial Infraction at Presentation

Abstract Background The potential relationship between cardiac troponin (cTn) fragment composition and the etiologies of myocardial injury indicate that characterization of cTn composition or targeting specific cTn fragments may provide diagnostic insights beyond total cTn levels and improve the diagnosis of myocardial infarction (MI). We analyzed the ternary cTnI–cTnT–TnC complexes (ITC), total cTnI and total cTnT in the circulation and compared the performance of the novel ITC complex assays with the widely used high-sensitivity (hs)-cTnI and hs-cTnT in differentiating MI patients at presentation. Methods Plasma samples were collected from 1210 patients presenting to the emergency department (ED) with symptoms suggestive of MI. The final diagnosis was adjudicated based on all available clinical records. Major cTn forms in the circulation were quantified using hs-cTnI, hs-cTnT, and ITC complex assays including long-cTnT ITC complex assay and hs-total ITC complex assay. We compared the performance of the ITC complex assays with hs-cTnI and hs-cTnT based on the 99th percentile upper reference limits (URLs), evaluated their area under the receiver operating characteristic curve (AUC), and assessed their ability to differentiate MI patients using established cut-off values. Results Among the study cohort, 138 (11.4%) patients were diagnosed with MI. The concentration of all cTn forms were significant higher in MI patients compared to non-MI patients. 86% patients had long-cTnT ITC complex concentration below the 99th percentile URLs, with the sensitivity 0.818 (95%CI: 0.746–0.874), specificity 0.943 (95%CI: 0.927–0.955), NPV 0.975 (95%CI: 0.964–0.983) and PPV 0.649 (95%CI: 0.575–0.716). Diagnostic accuracy, quantified by AUC values, was 0.959 (95% CI: 0.942–0.975) for the long-cTnT ITC complex, comparable to hs-cTnI (0.953, 95% CI: 0.934–0.971) and superior to both the hs-total ITC complex (0.889, 95% CI: 0.858–0.920, P < 0.001) and hs-cTnT (0.927, 95% CI: 0.904–0.948, P < 0.001). Using established cut-off values, the long-cTnT ITC complex assay classified 10% of patients as rule-in and 52% as rule-out, with a sensitivity of 0.993 (95% CI: 0.960–0.998), NPV of 0.998 (95% CI: 0.991–0.999), specificity of 0.972 (95% CI: 0.960–0.980), and PPV of 0.760 (95% CI: 0.678–0.826), which was comparable to hs-cTnI and better than hs-total ITC complex and hs-cTnT. In patients with a short chest pain onset time, the long-cTnT ITC complex assay demonstrated improved discrimination and enhanced diagnostic performance, as reflected by higher AUC values and more effective patient classification based on the 99th percentile URLs and established cut-off values. Conclusion The long-cTnT ITC complex assay demonstrated performance comparable to hs-cTnI and superior to both the hs-total ITC complex and hs-cTnT in distinguishing MI at presentation. Notably, its diagnostic advantages were more pronounced in patients at early presentation after symptom onset, highlighting its potential utility in optimizing rapid triage strategies in the ED.