High-sensitive cardiac troponin T (hs-cTnT) is a cornerstone for diagnosing acute myocardial infarction (AMI). However, it is often challenging to diagnose AMI in patients with elevated hs-cTnT before a rise or fall of hs-cTnT can be observed. The elevations of hs-cTnT are caused not only by AMI, but also by other cardiac or even non-cardiac diseases. Thresholds above the 99th percentile have been proposed to improve the specificity and to accelerate the rule in of myocardial infarction. This study aimed to find a more accurate cut-off value to rule in AMI in patients with elevated hs-cTnT.

Acute myocardial infarction (AMI) is a major cause of morbidity and mortality worldwide. In real clinical practice, early and accurate recognition of AMI is crucial to accelerate effective reperfusion therapy. High-sensitivity cardiac troponin T (hs-cTnT) is an important protein that regulates cardiomyocytes excitability, which can be proliferated in cardiomyocytes and released into the blood after myocardial injury or infarction. According to the fourth universal definition of AMI, a rise and/or fall of cTn values with at least one value above the 99th percentile URL is the essential precondition for diagnosing AMI. However, it is challenging for clinicians to diagnose AMI in patients with elevated hs-cTnT levels before a rise and/or fall of hs-cTnT values can be observed, particularly for those who present atypical symptoms and non-significant changes in electrocardiograms (ECG). When the 99th percentile upper reference limit (URL) is referred, it happens frequently that the elevations of hs-cTnT are not caused by AMI, but by other cardiac or even non-cardiac diseases. Therefore, thresholds above the 99th percentile have been proposed to improve the specificity and to accelerate the rule in of myocardial infarction.

This study aimed to find a higher and more accurate cut-off value of hs-cTnT to rule in AMI in a large volume of patients with elevated hs-cTnT.

Inclusion Criteria:

• Patients hospitalized from January 1,2015 to May 31,2023 in the First Affiliated Hospital of Nanjing Medical University with hs-cTnT concentrations over 14.0 ng/L were enrolled.

Exclusion Criteria:

• Patients who underwent major cardiac surgeries during the hospitalization.

Inpatients' data were obtained from hospital's Clinical Data Repository (CDR), which integrates patients' baseline characteristics, laboratory results, clinical diagnosis, and treatment information during the index hospitalization. And all of the patients hospitalized from January 1,2015 to May 31,2023 in the First Affiliated Hospital of Nanjing Medical University with hs-cTnT concentrations over 14.0 ng/L were enrolled.