Prospective randomised clinical trial definition

If the outcome of interest is uncommon, however, the size of prospective investigation required to estimate relative risk is often too large to be feasible. In retrospective studies the odds ratio provides an estimate of relative risk.

You should take special care to avoid sources of bias and confounding in retrospective studies. Prospective investigation is required to make precise estimates of either the incidence of an outcome or the relative risk of an outcome based on exposure. Case-Control studies are usually but not exclusively retrospective, the opposite is true for cohort studies.

The following notes relate case-control to cohort studies:. This would make the results of a trial unreliable, as it could exaggerate or hide the effects of the treatment. Next Section: What is an observational study? What is a randomised clinical trial? Use the following four questions to determine the difference between a clinical study and a clinical trial: Does the study involve human participants?

Are the participants prospectively assigned to an intervention? Is the study designed to evaluate the effect of the intervention on the participants? Is the effect being evaluated a health-related biomedical or behavioral outcome? Note that if the answers to the 4 questions are yes, your study meets the NIH definition of a clinical trial, even if… You are studying healthy participants Your study does not have a comparison group e.

Resources to Clarify the Definition Case Studies These simplified case studies illustrate the differences between clinical trials and clinical studies. Decision Tree Print this decision tree for an easy reference for the four questions that identify a clinical trial. This page last updated on August 8, National Center for Biotechnology Information , U. Author manuscript; available in PMC Dec 1. Locascio , PhD 2. Joseph J. Author information Copyright and License information Disclaimer. Copyright notice.

The publisher's final edited version of this article is available at BJOG. See other articles in PMC that cite the published article.