People who call emergency medical services (EMS) with chest pain or other possible heart-related symptoms are often taken to hospital for further testing. However, only a small proportion of these patients are ultimately diagnosed with a serious heart condition such as a heart attack. This means that many patients undergo hospital transport and evaluation even though their risk is low.

In hospitals, a blood test called high-sensitivity cardiac troponin is commonly used to help diagnose or rule out heart attacks. It is not yet well established whether this type of test can be used safely and effectively earlier, in the prehospital setting.

This study will investigate whether it is feasible to measure high-sensitivity troponin in the ambulance and how well the test can identify patients at low risk of serious heart conditions. A small blood sample will be taken as part of routine care and analyzed using a portable device. The test result will not be used to guide treatment or decisions during the study.

The study will assess how well the test predicts heart-related events within 30 days and how practical it is to perform the test in real-life emergency settings. The results may help guide future research on how to improve early assessment and decision-making for patients with suspected heart disease.

This is a prospective observational diagnostic accuracy and feasibility study conducted in the Central Denmark Region.

Adult patients assessed by participating emergency medical services (EMS) units with symptoms suggestive of acute coronary syndrome (ACS), without ST-segment elevation on the prehospital electrocardiogram, and managed with planned transport to hospital are eligible for inclusion.

During routine EMS assessment, a venous blood sample (<0.5 mL) is obtained and analyzed using a portable point-of-care device for measurement of high-sensitivity cardiac troponin I (hs-TnI). The measurement is performed according to manufacturer instructions and local procedures. Troponin values are recorded for research purposes only and are not used to guide clinical decision-making. EMS personnel are not provided with interpretation guidance or clinical thresholds for hs-TnI.

Clinical assessment, treatment, triage, and transport decisions follow standard regional protocols and are independent of study participation.

Clinical data are obtained from prehospital records and hospital electronic health records. Final diagnoses, including acute coronary syndrome, are determined based on standard clinical evaluation, including serial in-hospital troponin measurements and other diagnostic procedures as clinically indicated.

The primary analysis evaluates the diagnostic performance of prehospital hs-TnI for identifying acute coronary syndrome and predicting major adverse cardiac events within 30 days. Diagnostic performance will be reported using sensitivity, specificity, positive and negative predictive values, likelihood ratios, and area under the receiver operating characteristic curve.

Secondary analyses assess associations between hs-TnI concentrations and clinical outcomes, including hospital admission, length of stay, coronary angiography, coronary revascularization, and 30-day mortality.

Feasibility outcomes include the proportion of successful blood sampling, the proportion of valid measurements, and the time from patient contact to availability of the biomarker result.

The study is designed to generate feasibility and diagnostic accuracy data to inform the design and statistical planning of future interventional studies in the prehospital setting.

The study has been assessed by The Central Denmark Region Committees on Health Research Ethics, which determined that the project does not require notification or approval under Danish legislation.

Inclusion Criteria:

• Age 18 years or older
• Assessed by one of the participating EMS units equipped for POCT sampling
• Presentation with symptoms suggestive of acute coronary syndrome
• Planned transport to hospital for further evaluation

Exclusion Criteria:

• ST-segment elevation on prehospital electrocardiogram
• Clinical condition requiring immediate life-saving intervention precluding study procedures
• Interhospital transport
• Prior inclusion in the study within 30 days

Patients are recruited from the prehospital emergency medical services (EMS) system in the Central Denmark Region, Denmark. Participants are identified during routine ambulance missions by EMS personnel in units equipped with point-of-care testing (POCT) devices and trained in study procedures. The study population reflects real-world prehospital patients encountered in a publicly funded, tax-supported healthcare system with universal access to emergency care. Patients are included consecutively during the study period based on operational availability of participating EMS units.

Individual participant data will not be made publicly available due to Danish data protection legislation (GDPR) and regional regulations governing the use of health data. The study relies on linked prehospital and hospital registry data obtained under specific approvals, which do not permit sharing of individual-level data outside the secure research environment. Data access is restricted to authorized personnel. Aggregated and anonymized results may be shared upon reasonable request and subject to relevant approvals.