Limitations
This study has some limitations. First, we may have missed important low value practices that were not identified in the scoping review or suggested by clinical experts. For example, no practices related to surgical procedures were identified although significant variability in orthopedic surgical intensity among trauma centres was reported in a recent study.92 Second, by using a staged approach for the inclusion of studies with the most rigorous evidence, we may have missed some relevant studies. However, for practices with associated systematic reviews or RCTs, we also included studies with a lower level of evidence that were published more recently. Lastly, studies with a high level of evidence were not found for all practices and most studies were of low methodological quality or had a high risk of bias.