Information on Clinical Research Studies:
What Is a Clinical Study?
A clinical study involves research using human volunteers (also called participants) that is
intended to add to medical knowledge. There are two main types of clinical studies: clinical trials
(also called interventional studies) and observational studies (studies that collect data only such
as surveys). ClinicalTrials.gov includes both interventional and observational studies.
Clinical Trials
In a clinical trial, participants receive specific interventions according to the research plan or protocol created by the investigators. These interventions may be medical products, such as drugs or devices; procedures; or changes to participants’ behavior, such as diet. Clinical trials may compare a new medical approach to a standard one that is already available, to a placebo that contains no active ingredients, or to no intervention. Some clinical trials compare interventions that are already available to each other. When a new product or approach is being studied, it is not usually known whether it will be helpful, harmful, or no different than available alternatives (including no intervention). The investigators try to determine the safety and efficacy of the intervention by measuring certain outcomes in the participants. For example, investigators may give a drug or treatment to participants who have high blood pressure to see whether their blood pressure decreases.
Clinical trials used in drug development are sometimes described by phase. These phases are defined by the Food and Drug Administration (FDA).
Some people who are not eligible to participate in a clinical trial may be able to get experimental drugs or devices outside of a clinical trial through expanded access. See more information on expanded access from the FDA.
* National Library of Medicine (NLM) and ClinicalTrials.gov. (2019, March) Learn About Clinical Studies. Retrieved October 3, 2019, from http://www.clinicaltrials.gov/.