Run in period

Run-in period is a period before a clinical trial is commenced, it can be passive "when a placebo or no treatment is given" or active "when treatment is used". The clinical data from this stage of a trial are only occasionally of value but can serve a valuable role in screening out ineligible or non-compliant participants, in ensuring that participants are in a stable condition, and in providing baseline observations. A run-in period is sometimes called a washout period if treatments that participants were using before entering the clinical trial are discontinued.