Defining the Study Cohort: Inclusion and Exclusion Criteria
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A study cohort is a group of individuals with common characteristics who are initially defined, composed and then examined or tracked over a given time period. In a clinical trial, outlining the study cohort begins with clearly defined, study-specific eligibility criteria. Inclusion criteria and exclusion criteria together determine who is eligible to participate in the study. These selection or eligibility criteria are determined during the planning phase of the study, with the study goals of the clinical trial in mind. Establishing eligibility criteria primarily requires the precise definition of the primary and secondary study outcomes, which provides guidance for the sample size of the clinical trial that is required to detect a significant difference between the study intervention and control group. The eligibility criteria should be sufficiently narrow to ensure internal study validity, but sufficiently broad to allow for generalizability of the study results to the general population. In addition, eligibility criteria must be chosen carefully to allow for the feasible recruitment of study subjects into the clinical trial and must meet ethical criteria established by the National Institutes of Health (NIH).
KeywordsBelmont Report CONSORT Criteria Eligibility Exclusion Inclusion Patient selection
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