The incidence of MACE was lower in the current study (3.1%) than in PRASFIT-ACS  (9.4%). Conversely, the incidences of cardiovascular death (1.8%), all-cause death (2.2%), and non-fatal ischemic stroke (0.7%) were slightly higher in the current study than those in PRASFIT-ACS  (1.3, 1.8, and 0.4%, respectively). The explanation for these differences may involve: (1) the difference in the duration of the observation period in each study, and (2) that PRASFIT-Practice I was an observational study reflecting the clinical use of prasugrel in a real-world setting. Thus, patients with severe conditions were included, whereas in the PRASFIT-ACS , such cases were excluded. The incidence of non-fatal MI was low in this study, which may also explain the low incidence of MACE compared with PRASFIT-ACS . A possible reason for this may be that naturally occurring MI as well as events judged according to CAG findings and markers of myocardial injury, including creatine kinase-MB, were evaluated in PRASFIT-ACS ; however, only cases of MI reported by investigators under the actual conditions of use were evaluated as events in this study.