There could be a variety of answers to the title drawn from the repertoire of popular music, ranging from a dusting to a life embodied. In the setting of evidence-based medicine … like almost every question that’s asked … the answer is probably “It Depends”.
If our question regards the use of a significantly toxic or complex therapy, where other options exist, I’d be wanting a fair bit of ‘good’ evidence to swing me to using the new thing. For example, if you’re trying to prevent mucositis after chemotherapy, and wanting to use a specialised intraoral laser needing extra visits three times per week and a team of dentist and dental therapist to deliver it, I’d be tempted to demand high quality randomised clinical trials showing it was clinically effective, practical and worth the resource investment. If you were trying to do the same thing, but the intervention was the delivery of flavoured ice intraorally … yep … I do mean giving kids and ice-pop or a slushy … then I’d be much happier to take some adult trials and a bit of data from somewhere to say kids weren’t harmed by frozen squash.
What’s going on underneath the engine here is a way of trading ‘risks’. We are comparing the chance of positive and negative outcomes, and our confidence in the estimates of those. Now this is too simple a way to split these, but the ‘positive’ generally refers to better patient outcomes, including experience as well as medical measurables, and ‘negative’ refers to the iatrogenic harms, the monetary expenditures, and the resource use, including the ‘opportunity costs’. ‘Opportunity cost’ is the posh way of saying ‘A dentist can’t be in two places at once’
If you use this type of lens to look at decisions where what’s acceptable level of evidence somewhere is unacceptable elsewhere, it may help demystify, and subsequently allow you to explain much more clearly how things are being concluded and save angst.