Control Subject in Clinical Research

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In scientific research, a control subject is someone who is used to provide a basis for comparison. When the individuals who serve as control subjects are aggregated together they are called the control group.

Control subjects may be used in clinical trials to gain more information about various health conditions and their treatments. Often, but not always, the control subject is a healthy volunteer who has no pre-existing medical conditions.

Control subjects are typically subject to inclusion criteria, meaning they must possess certain characteristics to fit the bill for the study at hand, and exclusion criteria, which are characteristics that might exclude them from acting as a control subject. Such characteristics include age, gender, medical condition and medical history.

How a Control Subject May Be Used

There are different ways in which a control subject may be used:

As a comparison to people with a particular condition: Control subjects may belong to a group of healthy individuals who are being studied to see how their symptoms, traits, or behaviors compare to a group of individuals who suffer from a certain health disorder. People who volunteer to serve as healthy control subjects are often paid for their participation in the study.

Receiving a placebo: In clinical trials regarding the safety and effectiveness of a new medication or treatment, control subjects will be individuals who have the same health problem as the study subjects, but who receive a placebo or undergo a "sham" treatment. This group may be referred to as "placebo-controls." In such studies, subjects are typically randomly assigned to either the treatment group or the placebo control group.​​

Comparison of a new to an old treatment: In this type of study, control subjects would receive an already proven form of treatment and then be compared to individuals receive a novel form of treatment.

Study Design Types and Effect on Control Subjects

There are a couple of different types of study designs that involve control subjects:

  • Blind design: Control subjects do not know they are in the control group or receiving a placebo.
  • Double-blind design: Neither the control subjects nor the people administering the treatment know who is receiving the placebo drug or sham or a comparison treatment.

Protection of Control Subjects

In quality clinical studies, there are processes in place to provide protection from harm to control subjects. Typically, informed consent is required, in which participants are given information about any possible risks or benefits of participating in the study. Some studies must have their designs, and therefore the treatment of control subjects approved of by institutional review boards (IRBs) and/or by various federal agencies before they can be conducted.

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