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Human Subjects

Policies & Guidance

Enrollment Into Competing Studies

Two studies should count as “competing” when the following two conditions hold:

  • The inclusion and exclusion criteria overlap significantly: in other words, a significant percentage of the patients who will qualify for enrollment in one (or both) of the studies will also qualify for enrollment in the other, and
  • The population of patients eligible for the studies is limited, in other words, if both studies successfully recruit, they will have enrolled a significant percentage of all individuals who are eligible for at least one of the studies.

Some cases will be clear, as when two studies being conducted would recruit every eligible patient at the proposed sites. Of note, competing studies are typically ones where potential subjects must have specific diseases or stages of disease to qualify.

Studies would not count as competing where the inclusion and exclusion criteria are so broad that many persons in the general population would qualify as potential subjects, or where normal volunteers are needed for two different studies. In both cases, criterion (b) will not be satisfied.

Considerations / Approaches:

When an investigator has determined that a situation of competitive enrollment exists, the following shall be considered when designing a sound recruitment strategy:

Participant choice – In an effort to uphold the Belmont Report principle of respect for persons, investigators need to consider subject autonomy. As such, investigators should disclose to the potential participant the existence of any and all competing studies for which the participant qualifies and of which the investigator is aware. Investigators shall not withhold information about alternative studies, nor shall investigators actively avoid learning about other available studies. As part of the informed consent process, potential subjects must be made aware of alternatives, including other research projects for which they may qualify.

Recruitment goals – Unless recruitment goals may be reasonably achieved, the possible benefit to science and society is reduced or eliminated. Accordingly, investigators are encouraged to consider a strategy that does not undermine the ability of a trial to achieve its recruitment goals. A departmental approach is suggested below.

Department, division or unit priority – Relevant IU departments, divisions, and units are encouraged to implement mechanisms to avoid allowing multiple studies to compete for the same limited pool of potential subjects. To do so, units may consider implementing methods for prioritizing which studies should be started or postponed, based on issues of recruitment, when necessary.

Bias – The IRB is required to assess a trial’s potential benefits to science and society and thus potential bias that could undermine study results is of rightful concern to the IRB. As such, investigators have an obligation to consider whether participants are representative of the wider population, and to ensure an appropriate study design and recruitment methods. While a proposed recruitment strategy may involve allowing investigators and/or subjects to choose between studies, investigators should be prepared to justify the proposal, including how the proposed methods preclude the potential for bias.


Investigators, when faced with a situation of competitive enrollment, must present a recruitment strategy to the IRB that considers the above approaches and offers justification as to the chosen method(s).

The IRB will utilize this guidance to consider the proposed strategy, and may approve, require revisions to, or disapprove the proposal as is needed to ensure the adequate protection of subjects.

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