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What is a Control or Control group? Understanding the Basics of Randomized Clinical Trials

In a randomized clinical trial participants are arbitrarily assigned to control or study group - no biases are involved here. Source: ucsf.edu

To take a well informed decision to participate or not to participate in a clinical trial, it is essential that you clearly understand the various terms used by the clinical research coordinator while trying to explain the various aspects and protocol of the research study. Though, the research coordinator will try to explain these terms in the best possible way, it always helps to have a fair knowledge beforehand. Hence, we present the post on “what is a control or control group,” the latest addition in our ongoing clinical primer series.

A control or control group may be defined as a group of clinical trial participants who do not receive the drug or treatment being investigated as part of the trial.

To explain the above statement in simple layman’s language, researchers of certain clinical trials prefer to divide the participants into 2 groups, one the experimental group and the other called the control group. During the course of the clinical trial, the participants of the experimental group are administered with the study drug or treatment procedure, whereas the control group is not provided with the study drug.

So “Why is a control group required?” You might wonder why are participants enrolled into a medical research if they will not be given the experimental treatment at all or what purpose do the control participants serve? Well, actually the control group plays an essential role in several clinical studies and serves as standard or baseline for ascertaining the effectiveness of the study drug. By comparing the data obtained from the experimental group with that of the control group, the researchers can nullify the external factors (factors other than the study drug) that may be affecting the overall condition of the participants. For example, in a study involving a drug for asthma patients, by having a control group the researchers can be assured that the improvements in the condition of the participants is caused by the drug and not by factors like change in weather and/or season.

Are the inclusion/exclusion criteria for control group and experimental groups different? No, in fact, according to clinical trial protocols there must be no difference in the participants of the 2 groups. The idea is to keep all variables other than the drug administered as similar as possible.

So How are the two groups selected?

The selection of participants into experimental or control group is completely randomized (akin to tossing the coin) and many times decided by a computer based program. These studies are hence, called as randomized studies. You have a 50:50 chance of being a part of either of the groups. Also, in many such trials, no one from the research team can in anyways influence the selection process (a process known as blinding).

What kind of treatment do the participants of control group receive?

The participants of the control group will not be provided with the experimental drug. Apart from that, depending upon the study protocol, the participants either may be administered with the presently established standard form of treatment or may be administered with a placebo (learn more about  “What is a placebo”).

How does this information affect me?

Now several studies include control and experimental groups; and there is no way, through which you can determine what group you will be selected. Hence, always enquire with your research coordinator whether the clinical trial includes control groups or not and participate in the trial only if you are comfortable with the fact that you may not really get to test the new drug and be just a part of the control group.

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  2. What Should People Consider Before Participating in a Trial? Understanding the Basics of Clinical Trial Studies
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  4. What are Side Effects and Adverse Reactions in Clinical Trials?
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