Study design

Use the design that will generate a higher level of evidence where possible.

For example, when comparing between two interventions, randomised controlled trials (RCTs) are usually better than observational studies (e.g. cohort studies) because there are less confounding variables.

In a clinical trial, control groups should at least receive standard active treatment. *

‘Placebo’ or ‘no-treatment’ may be used as a control group if: ^(5,6)

• There are currently no proven effective standard intervention available; or
• There are compelling scientific reasons for using placebo or no-treatment control groups, AND doing so will not cause more harm to subjects compared to using standard active control.

For more information about different types of control groups, refer to the U.S. FDA Drug study designs information sheet.

* It is debatable whether ‘standard treatment / care’ should be the best existing treatment in the world, or one that is available locally. In very poor or rural areas, ‘standard treatment’ may be non-existent and clinical research is seen as opportunities for people to access better standards of healthcare. However, if ‘standard’ healthcare benefits offered as part of research are not sustainable or accessible once a study is completed, this could lead to harm. The choice must be carefully assessed on a case-by-case basis. ⁽⁷⁾

In a clinical trial, there should be genuine uncertainty over which intervention arm is better.

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