Evidence-appraisal glossary
Explanatory trial
A randomized trial designed to test whether a treatment can work under ideal, tightly controlled conditions, using strict eligibility, close monitoring, and high protocol adherence. It measures efficacy rather than everyday effectiveness.
Also called: efficacy trial.
By selecting a narrow, well-defined group of participants and enforcing the protocol closely, explanatory trials give the treatment its best chance to show a true biological effect and keep confounding low. This is the classic design behind most drug-approval studies. The cost is generalizability: results from a carefully filtered population under ideal conditions may not carry over to the messier range of patients and adherence seen in routine care.
This is a plain-language methodology definition for reading research. It is general education, not medical advice.