NR: not reported. ACS: acute coronary syndrome. MI: myocardial infarction. CCU: coronary care unit. ER: emergency room. NSTEMI: non ST-elevation myocardial infarction. Median time since start of symptom at baseline in hours. Median symptom time 20 h if <20% change, and median symptom time 12 h if >20% change. Symptom time <8 h or <12 h respectively required for inclusion in study. 16% had a <20% cTnI change at 6 h.