Mandatory Companion Studies


Some national study groups and study sponsors want to require that participants in treatment studies also participate in other research activities, such as registries, data repositories, and collection of biological specimens and/or genetic materials. Such mandatory companion studies raise a serious ethical issue and conflict with regulations pertaining to human subjects research:

  • Participation in research should be voluntary.
  • Undue pressure is created if subjects are told they cannot receive a potentially beneficial (though experimental) treatment unless they also agree to participate in the additional study.

Preferred Method for Including a Companion or Ancillary Study

Participation in ancillary studies should not be required for enrollment in a study involving experimental treatment that might benefit subjects. The IRB generally will not approve such linked studies, but will instead ask that the ancillary study be made optional.

How to make provisions for separate voluntary consent:

  • The preferred method is to use a separate consent form.
  • Alternatively, describe the ancillary study in a separate section within the main consent form. Provide separate lines for subjects to initial if they agree to participate in the ancillary study.

Exceptions: When a Mandatory Companion Study May Be Allowed

Under the circumstances described below, participation in a companion study may be required as a condition of enrollment in the main study. Eligible participants who from the onset do not wish to participate in the ancillary study may be denied enrollment in the main study.


Last updated: September 27, 2023