The use of serial measurement of cardiac troponin (cTn) is recommended by international guidelines for the diagnosis of myocardial infarction (MI) since 2000. However, the are some relevant differences among the recommendations proposed by the three different international guidelines published in 2020-2021 for the management of patients admitted to the Emergency Department (ED) with a clinical suspicion of a non-ST-segment elevation MI (NSTEMI). In particular, there is no agreement among these authoritative international guidelines about the cut-off or absolute change values to be used for diagnosis of MI. Another important controversial issue is whether there are, at present time, sufficient evidences on the diagnostic accuracy and cost effectiveness related to cut-off values suggested for the most rapid algorithms (0-1 or 0-2 hours) recommended for the rule-in/rule-out of NSTEMI. Finally, another important issue concerns the possible bias existing between the demographic and clinical characteritics of the patients enrolled in some multicenter trials compared to those routinely admitted to ED of the city Hospitals of some European countries, including Italy, for the diagnosis of NSTEMI. Considering the recommendations from these international guidelines, the Study Group of Cardiac Biomarkers, supported by the Italian Scientific Societies SIBioC Società Italiana di Biochimica Clinica), ELAS (Italian Society of the European Ligand Assay Society) and SIPMeL (Società Italiana di Patologia Clinica e medicina di Laboraratorio), decided to revise the document previously published in 2013 about the management of patients admitted to ED with suspect NSTEMI, and so to prepare suggestions more specifically designed for the clinical institutions operating in the healthcare system in Italy.