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A clinical trial must follow a design that is chosen based on the goals stated in the research protocol.
Government agencies stipulate that an appropriate method for a clinical trial must be selected. Two of the main methods for conducting clinical trials are the uncontrolled clinical trial and the controlled clinical trial. Controlled clinical trials can be conducted in different ways.
An uncontrolled clinical trial is one without a control group, meaning that all the participants receive the same treatment.
By contrast, a controlled clinical trial separates participants into comparison groups. One group (the control group) receives the standard treatment or placebo, while the other group (the experimental group) receives the study treatment.
Several groups may receive the study treatment, for example, if different doses are being tested, or if the study treatment is given alone to one group, and in combination with another treatment to another group.
Different controlled clinical trial methods determine:
The clinical trial investigator and the research team know which participants are in the experimental group (receiving the treatment) and which are in the control group (receiving the placebo), but the participants do not know. In some cases, it may be the study participants who are aware of their group assignment, while the study physician and research team are not.
The single-blind and double-blind methods prevent research team members and/or participants from affecting trial results by accident because of their expectations or bias concerning the treatment.
When participants are assigned at random to the different groups in a controlled clinical trial, usually using random selection software, we refer to the study as a randomized controlled clinical trial.
Controlled clinical trials, whether randomized or non-randomized, open, single-blind or double-blind, can be conducted using either the crossover or parallel method.
Project participants receive the standard treatment (or placebo) followed by the study treatment or vice versa (randomized order). No doses are given during the period between the two treatments. This action ensures that there are no possible lasting effects from the first treatment.