Cardiac troponin is central to the diagnosis of myocardial infarction and high-sensitivity cardiac troponin (hs-cTn) assays are the preferred choice for the assessment of patients with suspected acute coronary syndrome.

Since the introduction of hs-cTn assays in Europe in 2010, most hospitals have switched from contemporary sensitive cardiac troponin assays to a hs-cTn assay. The implementation of hs-cTn assays has led to an increase in the number of patients identified with myocardial injury. Although both hs-cTnI and hs-cTnT assays are recommended in current guidelines, the impact of switching from a hs-cTnI assay to a hs-cTnT assay on clinical practice is unknown. At this point, no studies have evaluated the impact of implementing sex-specific hs-cTnT thresholds on the diagnosis of myocardial infarction and outcome in clinical practice.

The investigators propose to determine the proportion of patients with and without myocardial injury admitted to the hospital before and after implementation of a hs-cTnT assay and to evaluate the impact on investigations, care and clinical outcomes in consecutive patients with suspected acute coronary syndrome.

Inclusion Criteria:

• Age 18 years and over
• Symptoms of possible acute coronary syndrome
• High-sensitivity cardiac troponin measured at presentation

Exclusion Criteria:

• Insufficient clinical information to perform record linkage
• Previous enrolment in the study
• Patients with ST-segment elevation myocardial infarction (STEMI)

All patients presenting to an Emergency Department or an Acute Medical Unit in NHS Lothian between October 25th 2020 and October 25th 2022 where the attending clinician measures cardiac troponin for suspected acute coronary syndrome will be identified by NHS Lothian staff or the research team using an existing screening tool embedded into the ordering of cardiac troponin testing.

We will compare the clinical impact of two guideline recommended high-sensitivity cardiac troponin assays in routine health care. We will not seek individual patient consent as this is an evaluation of a change in routine clinical care using approved tests, there are no specific research procedures, and we wish to evaluate performance in those patients in whom clinicians apply the test to avoid selection bias.