consider performing a single high-sensitivity troponin test only at presentation to rule out NSTEMI if the first troponin test is below the lower limit of detection 1.2.5.4 Ensure that patients understand that a detectable troponin on the first high-sensitivity test does not necessarily indicate that they have had an 1.2.5.5 Do not use biochemical markers such as natriuretic peptides and high- sensitivity C-reactive protein to diagnose an ACS. [2010] 1.2.5.6 Do not use biochemical markers of myocardial ischaemia (such as ischaemia-modified albumin) as opposed to markers of necrosis when assessing people with acute chest pain. [2010] 1.2.5.7 When interpreting high-sensitivity troponin measurements, take into account: the clinical presentation the time from onset of symptoms the resting 12-lead ECG findings the pre-test probability of NSTEMI the length of time since the suspected ACS the probability of chronically elevated troponin levels in some people that 99th percentile thresholds for troponin I and T may differ between sexes. 1.2.6 Making a diagnosis 1.2.6.1 When diagnosing MI, use the universal definition of myocardial infarction. This is the detection of rise and/or fall of cardiac biomarkers values [preferably cardiac troponin (cTn)] with at least one value above the 99th percentile of the upper reference limit and at least one of the following: symptoms of ischaemia new or presumed new significant ST-segment-T wave (ST-T) changes or new LBBB development of pathological Q waves in the ECG imaging evidence of new loss of viable myocardium or new regional wall motion abnormality identification of an intracoronary thrombus by angiography. [2010, amended 1.2.6.2 When a raised troponin level is detected in people with a suspected ACS, reassess to exclude other causes for raised troponin (for example, myocarditis, aortic dissection or pulmonary embolism) before confirming the diagnosis of ACS. 