Clinical trials and clinical studies—What’s the difference? Hart’s Good Clinical Practice glossary series

Welcome to the Hart GCP knowledge series where we are reviewing key definitions found in the Good Clinical Practice (GCP) guidelines. In this entry, we are looking at the terms Clinical Trial and Clinical Study.

People often ask me what the difference is between these two terms.   In fact, usually they are considered interchangeable, but there are slight caveats to that interpretation.


The ICH E6 guidelines define a clinical trial/study as:

Any investigation in human subjects intended to discover or verify the clinical, pharmacological, and/or other pharmacodynamic effects of an investigational product(s), and/or to identify any adverse reactions to an investigational product(s), and/or to study absorption, distribution, metabolism, and excretion of an investigational product(s) with the object of ascertaining its safety and/or efficacy. The terms clinical trial and clinical study are synonymous.”

This definition applies generally to investigation of medical devices as well as pharmaceuticals intended for sale in countries that use ICH guidelines. Regulatory agencies in the US (FDA), Europe, and other countries use these guidelines to standardize evaluations of medical products prior to their approval for sale.


The National Institute of Health’s registration website for clinical trials, uses a definition with a bit more granularity because it sanctions a wide range of research studies. These studies are intended to add to the body of scientific and medical knowledge and are not necessarily related to evaluations of a product intended for sale. The website indicates that:

“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. includes both interventional and observational studies.”

The distinguishing characteristics of this definition are the terms interventional and observational. An interventional study involves researchers testing some kind of treatment or intervention, like a drug, device, or behavioral modification, and study participants are assigned specifically to receive that intervention, when they may not have if they weren’t in the study. An observational study may evaluate a treatment as part of routine care, but the intervention isn’t assigned to the patients as a part of the study. These studies often follow patients for some period and evaluated health outcomes related to the patient population.


So, you can use the terms clinical trial and clinical study interchangeably in most situations where you are working on a study for which the FDA or other regulatory agency requires compliance to ICH or GCP guidelines, but be aware that an NIH study may use slightly different terminology when referring to a clinical trial as an interventional study.

Thanks for tuning in to this episode of Hart Clinical Consultants’ glossary series!

Next time, we will explore comparator products, also known as study controls.

We Recently Updated Our Privacy Policy