A-006 Diagnostic performance of an investigational high-sensitivity cardiac troponin T and long-T ITC troponin complex assays for acute myocardial infarction in females and males

Abstract

High sensitivity cardiac troponin T and I (hs-cTnI, hs-cTnT) immunoassays measure the approximate total amount of the targeted troponin subunit and are used to aid in the diagnosis of myocardial infarction (MI). In the United States there is only one manufacturer who has an FDA-cleared hs-cTnT assay. Additionally, there is emerging evidence that selectively measuring the ternary troponin complex containing predominantly intact cTnT (long-T ITC) concentrations may provide more rapid detection of acute myocardial infarction (MI). In this study, we assessed the diagnostic performance of an investigational Mindray CL-1200i hs-cTnT chemiluminescence immunoassay for type 1 MI and type 2 MI (T1MI, T2MI) compared to our standard of care Abbott Alinity hs-cTnI assay and investigational Mindray hs-cTnI assay. We also investigated whether the long-T ITC complex assay can provide additional diagnostic specificity. Study participants presented to our emergency department with suspected acute coronary syndrome and were enrolled in the ‘Mindray hs-cTnI Assay Analytical and Clinical Evaluation for the Diagnosis and RIsk Assessment of Myocardial InfarctIon’ (MERITnI) (NCT05853042) trial. Lithium heparin plasma samples were collected for the measurement of long-T ITC complex, hs-cTnT, and hs-cTnI on the Mindray CL-1200i platform chemiluminescence immunoassay at 0- and 2-hours. Package insert defined overall and sex-specific 99th percentile upper reference limits were utilized. All patients were adjudicated by predetermined clinicians for MI or no MI according to the 4th universal definition of MI. Our cohort included 882 patients, 35.2% presented with chest pain, 5.3% presented with an MI, with nearly equal T1MI (2.7%) and T2MI (2.6%). The Mindray hs-cTnT assay demonstrated an overall sensitivity of 93.6% (95% confidence interval, 86.6-100), specificity of 43.1% (39.8-46.5), positive predictive value (PPV) of 8.5% (6.1-10.9) and negative predictive value (NPV) of 99.2% (98.2-100) for MI at baseline. Using serial 0/2 hour measurements did not statistically change the diagnostic performance of the hs-cTnT assay. By comparison, the standard of care Abbott hs-cTnI assay had an overall sensitivity of 85.1% (74.9-95.3), specificity of 77.4% (74.5-80.2), PPV of 17.5% (12.5-22.4) and NPV of 98.9% (98.1-99.7) for MI at baseline. The Mindray long-T ITC complex had similar diagnostic performance to hs-cTnT, with a specificity of 56.8% (53.4-60.1) at baseline. Absence of overlapping confidence intervals between hs-cTnT and long-T ITC complex at baseline suggests a statistically higher specificity at presentation for long-T ITC. The Mindray hs-cTnT immunoassay demonstrated comparable diagnostic performance to the Alinity hs-cTnI immunoassay. Additionally, the long-T ITC complex may provide additional specificity for MI at presentation.