Randomized Control Trials
Scientist Explains with Dr. Tarek Rajji
April 14, 2021
Randomized Controlled Trials (RCTs) are clinical studies in humans that test whether a proposed treatment is beneficial and whether its benefits outweigh the harms or side effects.
Let’s consider an example where a clinical trial is testing a treatment X. The trial will typically include two groups, group A and group B. People assigned to Group A receive the treatment X that is being tested, which might be a drug, medical device or lifestyle program. People in Group B are the comparison group, where either they receive a “placebo” (i.e., no active treatment) or another typical, well-established treatment for the condition (let’s call this treatment Y) to test whether treatment X works better than or as well as treatment Y. A placebo typically “looks” like the active treatment but has no significant effects. For example, a clinical trial testing a drug for the treatment of Alzheimer’s disease might have a placebo that is a pill with the same colouring, sizing and labelling as the active drug, but with no active ingredients.
What does “randomized” mean? This means people in the study are randomly assigned (e.g., deciding by a “coin flip”) to Group A or B. So if there are 100 people in the study, 50 people would be randomly assigned to group A and 50 to group B. This helps to ensure the groups are as similar as possible in their age, gender, and other relevant attributes.
What does “controlled” mean? These clinical trials have at least one “control” or comparison group (e.g., Group B) where participants receive a placebo or the typical care for their condition. This helps researchers compare whether the proposed treatment X is safer and more effective than what the control group receives.
What does “blinded” mean? Participants and research team members—particularly those who are assessing the participants and those who analyze the outcomes of the trial and care for participants—are blinded to the treatment conditions. This means that they are unaware of whether a participant is receiving the treatment X being tested (i.e., they are in Group A) or not (i.e., they are in Group B). Blinding ensures that this knowledge does not influence the outcomes of the study. Blinding is only broken after the trial is complete or if there are safety concerns.
