The diagnostic utility of High-Sensitivity Cardiac Troponin T in acute coronary syndrome

Abstract

Background: Coronary artery disease (CAD), its acute form, and acute coronary syndrome (ACS) are the leading cause of death all over the world. For initial assessment of a patient with ACS, ECG, imaging techniques and serum biomarkers all contribute in confirming the diagnosis. Cardiac Troponin (cTn) I and T are the current gold standard for the detection of myocardial necrosis. However, there is also emerging evidence suggesting that with the use of sensitive or high-sensitive cTn assays, a blood sample collected 2 or 3 h after presentation might be appropriate for an earlier rule in and rule out diagnosis of AMI compared with the recommended second blood draw 6-9 h after admission using conventional Troponin assay. Aim: The aim of this study was to examine the ability of High-Sensitivity Cardiac Troponin T for early detection of AMI in comparison with conventional Troponin assay. In addition, to study the clinical utility of kinetic changes of High-Sensitivity Cardiac Troponin T for diagnosis of ACS. Methods: This study was conducted on sixty subjects. Fifty patients who presented to emergency department in Ain-Shams University Hospital complaining of chest pain were highly suspicious to have acute cardiac ischemia, having no or non-specific ECG changes and their Cardiac Troponin I level on admission was below the test threshold value (100 ng/L). In addition, ten subjects serving as a healthy control group were also recruited. The fifty patients were subdivided into subgroup A which included 16 patients, with hs-TnT < 14 ng/L (99th percentile) on admission. For this group no second sample was needed. The second subgroup B included 34 patients with hs-cTnT ≥ 14 ng/L on admission. After 6-8 h, patients of group I-B were reassessed by routine cardiac markers and hs-TnT, in addition to one case of group I-A who was highly suspicious to be MI. Later, patients were reclassified after confirmatory cardiological diagnosis into group C, including cases of UA (n = 17) and group D, representing cases of NSTEMI (n = 33). Results: Results of the current study revealed that median serum levels of hs-TnT showed highly significant difference between patients with ACS and healthy subjects, and also between patients with NSTEMI and those with UA. Receiver operating characteristic (ROC) curve analysis was applied to assess the diagnostic performance of hs-TnT in discriminating patients from control group. The best cutoff was 4.8 ng/L. This cutoff had a diagnostic sensitivity, specificity, PPV, NPV and efficiency of 96%, 100%, 100%, 83.3% and 96.7% respectively. Another receiver operating characteristic (ROC) curve analysis was applied to assess the diagnostic performance of hs-TnT for discriminating NSTEMI patients from UA patients. The best diagnostic cutoff for hs-TnT was 13.7 ng/L. This had a diagnostic sensitivity, specificity, NPV, PPV and efficiency of 97%, 88.2%, 93.8%, 94.1% and 94% respectively. Conclusion: Our study demonstrated highly significant absolute and relative kinetic changes in hs-TnT levels in patients with AMI. The hs-TnT can be used for early rule in patients with MI as it could detect 97% of cases with MI whose Troponin I was negative and could detect 100% of cases of MI after 6-8 h compared to Troponin I which could detect only 21.2% of cases. This can be of great importance in the future introduction and use of the new high sensitive assay as a non-invasive reliable diagnostic tool to replace the currently used invasive diagnostic techniques for patients with ACS.