EBM Episode 2: Outdated evidence

This is the second episode in our series on EBM. In it we explore what it means for evidence to be outdated.

Evidence is instrumental to ensure the efficacy of innovation in clinical care: new medicines, devices and diagnostics require evidence of their efficacy before they can be sold for clinical use.

Evidence could become outdated because clinical trials used to show efficacy rarely have enough participants to detect rare adverse events. For example, a new and effective medicine may kill 1 in 10,000 patients. It would gain approval because such rare event would not be detectable in a typical clinical trial.

Evidence could also become outdated when new data show that the efficacy is not as good as we thought. Post-market surveillance and trials that reproduce the research can reverse the results of the original trial.

When new evidence emerges about a superior alternative should lead to an update to reflect the new therapy. However, evidence is often not updated at all. When it is, the update process could take years. Every year, 7% of the evidence becomes outdated. We need faster, cheaper ways to update evidence.

How Quickly Do Systematic Reviews Go Out of Date? A Survival Analysis