Clinical Trial Design

Before a clinical trial can begin, the researchers conducting the trial must determine a design. The clinical trial design is the blueprint for how the study’s experiments will be conducted, including the number of volunteers required in each phase, the treatment plan, the kinds of controls that will be used in the study and how the data will be analyzed.

Why is Clinical Trial Design Important?

Clinical trials are expensive and time-consuming, so researchers want to be sure that a trial will generate enough data—of the right kind—to make solid conclusions regarding the product’s safety and effectiveness. A well-designed clinical trial provides this information without spending more time and money than necessary.

Types of Clinical Trial Designs

Researchers categorize clinical trial designs in many different ways. At the broadest level of classification, however, clinical trials can be separated into controlled trials and observational trials:

  • Controlled clinical trial design: A group of volunteers receiving the new treatment is compared to a control group of volunteers, who may be given a placebo or an existing treatment.
  • Observational clinical trial design: Volunteers are given the new treatment, but they aren’t compared to a control group. Instead, researchers monitor them for changes in their condition over time.

Randomized and Blind Clinical Trials

Among controlled clinical trials, many are designed to be “randomized” and “blind.” In a randomized trial, volunteers are arbitrarily assigned to either the treatment group or the control group. If the volunteers aren’t told which group they’ve been assigned to, then the trial is categorized as blind, as well. In some trials—known as “double-blind” studies—not even the medical professionals know which volunteers belong to which group.

When possible, most trials are designed to be controlled, randomized and double-blind; these design elements allow researchers to draw more definitive conclusions about the treatment in question.


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