Comparison of the cardiac troponin I-cardiac troponin T-troponin C complex and cardiac troponin I and T in distinguishing myocardial infarction using a single sample at presentation

Abstract Objectives The potential relationship between cardiac troponin (cTn) composition and etiologies of myocardial injury may provide diagnostic insights for myocardial infarction (MI). We compared the performance of novel ternary cTnI–cTnT–TnC complex (ITC) assays with high-sensitivity (hs)-cTnI and hs-cTnT in differentiating MI patients at presentation. Methods Plasma samples from 1,210 patients with suspected MI were collected. Major cTn forms were quantified using long-cTnT ITC complex, hs-total ITC complex, hs-cTnI and hs-cTnT assay. We compared the assay performance 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 using established cut-off values. Results A total of 138 (11.4 %) patients were diagnosed with MI. 86 % patients had long-cTnT ITC complex concentration below the 99th percentile URLs (sensitivity: 0.818, specificity: 0.943, NPV: 0.975, PPV: 0.649). AUC was 0.959 for long-cTnT ITC complex, comparable to hs-cTnI (0.953) and superior to hs-total ITC complex (0.889) and hs-cTnT (0.927). Using established cut-off values, the long-cTnT ITC complex assay classified 10 % of patients as rule-in and 52 % as rule-out (sensitivity: 0.993, NPV: 0.998, specificity: 0.972, PPV: 0.760), which was comparable to hs-cTnI and better than hs-total ITC complex and hs-cTnT. In early-presenting patients, the long-cTnT ITC complex demonstrated enhanced discrimination and improved diagnostic performance. Conclusions The long-cTnT ITC complex assay demonstrated performance comparable to hs-cTnI and superior to hs-total ITC complex and hs-cTnT in distinguishing MI using a single sample at presentation. These findings suggest its potential utility in improving risk stratification and triage strategies, particularly among early-presenting patients.