What are washout period and run in period of clinical trials？

Run in period and washout period are two commonly used concepts in clinical trials. They play an important role in trial design and data analysis.

Run in period: the lead-in period is a stage before the start of a formal trial, which is usually used to screen and exclude some participants who are not suitable for the trial. During the lead-in period, participants may receive a period of control treatment or other pretreatment to determine whether they meet the inclusion criteria of the trial. The data collected during this period will not usually be included in the final trial analysis, but it can help researchers identify those participants who may introduce confounding factors or affect the results in the trial.

Washout period: the washout period is a period of time set to exclude the influence of previously used treatments or drugs on the test results. During the washout period, participants stopped receiving the previous treatment to ensure that there was no residual treatment effect when they entered the trial. This can improve the internal effectiveness of the trial, so that the trial results can better reflect the real effect of the tested treatment, and will not be affected by other treatments.

The use of these two periods can help researchers better control the trial conditions, reduce confounding factors, and improve the reliability and effectiveness of the trial. The specific design of the lead-in period and the cleaning period will vary according to the nature of the test and research issues.