It is the job of the study recruiter to make sure each patient (a) meets eligibility criteria, and (b) fully understands and freely consents to the terms of participation in the study. Beyond that it is up to the patient to decide whether or not to participate in the study. You should not try to influence the patient’s decision one way or the other, but you should provide as much information and explanation as necessary to ensure they fully understand and genuinely consent to participate.
