Under the current clinical algorithm at Singapore General Hospital, ambulatory chest pain patients (CPP) receive an initial evaluation upon presentation to the ER that includes an ECG and blood draw. The lab spins and holds the blood to await add-on orders for cardiac markers if clinically-indicated. Other chest pain patients arriving by ambulance may have ECG taken in the ambulance and the results faxed ahead to the ER. Those that have an initial ECG consistent with an ST-elevation myocardial infarction (STEMI) receive immediate intervention. Patients that do not have STEMI identified are evaluated by an ER physician as soon as possible for clinical signs and symptoms of ACS, as well as, other diagnoses that require clinical treatment and/or hospital admission. Patients with suspected ACS require serial Troponin measurements as essential information for the rule-in or rule-out of a non-ST elevation myocardial infarction (NSTEMI). After seeing the patient, the ER physicians will add-on an hsTnT measurement to the sample drawn at presentation and held in the lab. This second hsTnT value is drawn two hours after presentation. Using the current standard of care hsTnT assay and the universal definition, an acute MI at Singapore General Hospital is defined as a troponin rise and/or fall with at least one value above 30pg/mL with symptoms suggestive of myocardial ischemia. There is no clear definition of the amount of rise or fall that is required. The reference range for a single troponin T measurement at Singapore General Hospital is currently defined as abnormal if above 30pg/mL. This study will compare the ARCHITECT hsTnI assay and Beckman Coulter ACCESS AccuTnI+3 assays using respective Abbott ARCHITECT and Beckman Coulter UniCel DxI 800 immunoassay systems, with hsTnT using Roche analyzer.