Should changes in inclusion and exclusion criteria remain constant during recruitment?

Should changes in inclusion and exclusion criteria remain constant during recruitment?

• A. They should remain constant
• B. They should be changed regularly
• C. They should be changed to adapt to recruitment
• D. They should be broadened to reach more patients

Answer: (A)

In a clinical trial, eligibility criteria define who can participate. Once recruitment starts, those criteria should stay fixed to keep the study population consistent and the results interpretable. If eligibility rules change mid-recruitment, you risk enrolling different types of participants over time, which introduces selection bias and makes it difficult to determine whether observed effects are due to the intervention or the altered criteria. This threatens the trial’s internal validity and can distort outcome comparisons. If changes are ever necessary, they must go through a formal protocol amendment with ethics approval and, if needed, re-consent, rather than occurring during ongoing recruitment.

In a clinical trial, eligibility criteria define who can participate. Once recruitment starts, those criteria should stay fixed to keep the study population consistent and the results interpretable. If eligibility rules change mid-recruitment, you risk enrolling different types of participants over time, which introduces selection bias and makes it difficult to determine whether observed effects are due to the intervention or the altered criteria. This threatens the trial’s internal validity and can distort outcome comparisons. If changes are ever necessary, they must go through a formal protocol amendment with ethics approval and, if needed, re-consent, rather than occurring during ongoing recruitment.