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Compensating Clinical Trial Participants: The Basics

Many clinical trial protocols include plans to compensate participants for their contribution to the research. According to FDA’s information sheet Payment and Reimbursement to Research Subjects, participant payment is a recruitment incentive and “is not considered a benefit that would be part of the weighing of benefits or risks.” Additionally, in its Informed Consent FAQs OHRP states that “remuneration to subjects may include compensation for risks associated with their participation in research and that compensation may be an acceptable motive for agreeing to participate in research.”

IRBs are tasked with reviewing the amount of payment, as well as the method and timing of disbursement, to ensure that the payment plan does not present potential undue influence. Participant compensation is often a complicated matter, so in this blog I’ll attempt to clarify some issues by shedding light on what an IRB considers during its review.


Bear in mind that compensation is not the same as reimbursement. Consider the following definitions:

Payment to subjects for participating in a study. It may be considered a recruitment incentive or a way of acknowledging the time and burdens imposed on subjects. Compensation plans require IRB review for assessment of whether they present any undue influence.

Re-payment for actual costs accrued by the subject while participating in the study (e.g., parking, transportation, mileage reimbursement, childcare, etc). This often requires the submission of receipts. Reimbursement does not generally raise the same concerns as compensation regarding undue influence since participants are being “paid back” money they have spent.

Compensation should be based on time invested and inconvenience. It may also be based on types of risks and procedures. However, compensation should not be considered a way of offsetting risks. The term undue influence is critical here; according to OHRP, undue influence “often occurs through an offer of an excessive or inappropriate reward or other overture in order to obtain compliance.”

IRB Review of Participant Compensation

IRB review should focus on whether the payment plan may compromise a participant’s evaluation of the risks or may affect the voluntariness of his or her decision to enroll and/or to remain in the study. Such concerns may arise, for instance, where an excessive and inappropriate amount of money is offered to participants.

When the research targets economically disadvantaged participants, payment proposals are typically subject to a higher level of IRB scrutiny. Payment may be more important for those to whom it will make a significant financial difference, so this participant population may be more susceptible to undue influence. On a similar note, for studies that enroll minors as participants, the IRB will want to know whether the compensation is intended for the parent/guardian, the minor participant, or both. When providing compensation to minor participants, the IRB will consider what is age-appropriate: for instance, gift cards may be appropriate for older children, while toys/gifts may be more appropriate for younger children.

Notably, the regulations do not define standard compensation limits. Because IRBs are tasked with evaluating compensation plans without defined regulatory standards, many IRBs have developed internal standards to provide for consistency in reviewing compensation.  It is important to understand your reviewing IRB’s standards and provide a rationale for your proposed plan.

Considerations When Developing a Compensation Plan

As mentioned earlier, each IRB maintains its own policies on participant compensation, so it’s important to know what is and is not permissible according to the study’s IRB of record. With that in mind, here are some general considerations for researchers developing a compensation plan:

In determining the amount of compensation to provide, take into account the amount of time each visit takes and the procedures to be performed at each visit. For instance, it may be appropriate to compensate participants a higher amount for study visits that require them to stay in the clinic overnight. Outside of the study visits, it may also be appropriate to compensate participants if they will be expected to complete detailed and time-consuming activities such as lengthy survey or study diary entries.

Credit for payment should generally be prorated, accruing as the study progresses, and payment should not be contingent on maintaining compliance over the course of the entire study. The reason for this is that withholding payment until completion of the study may adversely impact a subject’s right to withdraw from the study at any time. Payment may not always need to be exactly evenly prorated among study visits, but the overall plan should be assessed for potential undue influence. A completion bonus may be permissible as long as it is not so large that it unduly induces participants to stay in the study when they would otherwise have withdrawn. IRBs may have different policies for how large completion bonuses may be, based on, for instance, a percentage of the overall compensation.

Note that small incremental increases in compensation are not necessarily an indicator of potential undue influence and may be acceptable. Additionally, large differences may be acceptable if more involved and burdensome procedures are performed later in the study. Let’s look at a couple examples:

When developing any potential compensation plan, always measure it against the potential for undue influence and how it may impact a potential participant’s voluntariness and willingness to participate in the research.

If you have specific questions about your compensation plans for an upcoming study, contact Business Development or your Coordinator.



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