This study is a prospective, diagnostic, cohort study within the standard care of acute coronary syndrome (ACS) patients. It compares the analytical performance of Siemens® point-of-care high sensitive troponin I testing in venous, plasma and capillary sample types. The investigators hypothesize that there is a good correlation between the Siemens® POC HS cTnI assay results for the three sample types and that the bias between different POC sample types reduces from ~10% to ≤ 5% when using heparinized transfer device for the capillary sample.

In September 2019, the validation study 1.0 started, in which the cTnI result of the Siemens POC device on three sample types are compared. Interim analysis of the sample comparison was performed by regression analysis using Passing and Bablock, and calculating the Pearson correlation coefficient.

The Li-hep Plasma vs Li-hep venous blood show a very good correlation of 1.00-1.03 with an R of >0.99, so the results between these sample types can be used interchangeably. For the capillary sample vs the Li-hep sample (both blood and plasma) the slope is 8-12% higher. With a 8-12% higher response, the capillary test results may not be interchangeably used with the other 2 sample types.

It is remarkable that capillary samples give a higher response, since it was anticipated that the result may be slightly lower due to the possible dilution by interstitial fluid. The investigators hypothesize that the presence of the Li-heparin anti-coagulant in the venous draw lead to a slight reduction of the apparent cTnI concentration. By using a heparin coated transfer device for the capillary samples instead of an uncoated transfer device, this hypothesis will be tested.

Inclusion Criteria:

• Age 18 years or older.
• Referred to cardiac ED with chest pain suspected of ACS; inclusion at arrival (T=0) or one hour after arrival (T=1).
• Subacute STEMI or NSTEMI patients admitted at the CCU who have an indication for coronary angiography but do not need rescue/emergency PCI.
• STEMI patients who already underwent rescue/emergency PCI; inclusion post PCI.

Exclusion Criteria:

• Out of hospital cardiac arrest.
• Patients with sudden onset tachycardia and a frequency of 110 bpm or higher (supraventricular or ventricular).
• Patients who are hemodynamically unstable or in which an acute non-coronary diagnosis is suspected, e.g. pulmonary embolism, thoracic aortic dissection etc.
• Patients recently already admitted for the same set of symptoms at a previous healthcare institution before being transferred to the participating clinical site.
• Patients not willing or not able to provide informed consent due to their medical condition as judged by the physician.

All patients presented at our cardiology ED or coronary care unit (CCU) are eligible for inclusion if they are 18 years or older and suspected of having an ACS based on history, examination, ECG and regular troponin results from the central laboratory.