Participant Recruitment

Most Commonly Used Terms in Clinical Trials

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Samantha Trolli

Published 20 May 2022 - Updated 20 May 2022

Most Commonly Used Terms in Clinical Trials - Infiuss Health


        The terms and methods used in clinical trials can be daunting to a potential participant. In a previous blog, we discussed the barrier of health literacy and how it increases the gap between diversity and clinical trials. In this blog, we are reaching to close the gap by providing a source of reference for potential participants. Below you can find some of the most commonly used terms in clinical trials. 

Types of studies:  
Pilot Study: A small-scale version of the main study. The point of a pilot study is to ensure variables are set in place before the full-scale research begins. 

Observational Study: A type of a clinical study when the researcher only observes the participants/subjects and does not have control over the outcome. 

Prevention Trial: A trial focused on the prevention of disease. These trials offer treatment to healthy or high-risk individuals, offer them treatment, and follow them over many years to test if the treatment was preventative of a specific disease. 

Treatment Trial: When treatments are tested in phases to ensure they are safe and effective before being offered to the public. This type of trial is typically how new medications are studied. 

Cohort/Longitudinal Study: This type of study focuses on a group of people over a period of time. 

Case-Control Study: An example of an observational study. Two groups of participants/subjects are compared, one group with a disease (case) and the other without the disease (control). Researchers then aim to see the differences in their environments to determine a cause for the disease.  

Cross Sectional Study: Instead of following a group of participants over time, a cross-sectional study looks at multiple groups at one time. This is an easier way to execute a longitudinal study by having each group range in age. 

Types of Participant Groups:
Arm: A group of participants in a clinical trial that can either receive treatment/intervention or not receive any treatment/intervention based upon the trial’s methods. 

Cohort: A group of participants in an observational study. 

Control group: A group in a clinical trial in which participants do not receive the treatment/intervention for means of comparison to the treatment group. When participating in an observational study, the control group is the cohort without disease. 

Treatment/Experimental group: A group in a clinical trial in which participants do receive the treatment/intervention for means of comparison to the control group. 

Case group: In observational studies, a group of participants with disease or condition.  

General Vocabulary: 
Phase: The stage of a clinical trial, based on the FDA. There are five phases to a clinical trial: 

             Early Phase 1: Development and discovery of new treatments

             Phase 1: Answering the questions, is this treatment safe?

             Phase 2: The effectiveness of the treatment is evaluated while keeping safety in mind. 

            Phase 3: The new treatment is compared to existing treatments. FDA drug review occurs here. 

             Phase 4: Continuous research on the developed treatment to ensure safety and efficiency. 

Placebo: Often referred to as a sugar pill, a placebo is given to the control group for accurate comparison in the trial. Both the participants/subject and researcher do not know which group is receiving the inactive form of treatment (the placebo).  

Variables: In all types of research, variables are any thing (person, place, thing, or phenomenon) that the researcher is trying to measure. 

             Independent: A variable which the researcher controls in the study 

             Dependent: The variable that is changed due to the change in the independent variable. 

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