Improving the availability of stem cell donors - A letter and email intervention

Last registered on July 13, 2023

Pre-Trial

Trial Information

General Information

Title
Improving the availability of stem cell donors - A letter and email intervention
RCT ID
AEARCTR-0008938
Initial registration date
February 06, 2022

Initial registration date is when the trial was registered.

It corresponds to when the registration was submitted to the Registry to be reviewed for publication.

First published
February 07, 2022, 1:43 PM EST

First published corresponds to when the trial was first made public on the Registry after being reviewed.

Last updated
July 13, 2023, 7:17 AM EDT

Last updated is the most recent time when changes to the trial's registration were published.

Locations

Region

Primary Investigator

Affiliation
University of Tuebingen

Other Primary Investigator(s)

PI Affiliation
University of Tuebingen
PI Affiliation
Johns Hopkins University, Carey Business School
PI Affiliation
University of Technology Sydney
PI Affiliation
University of Cologne

Additional Trial Information

Status
In development
Start date
2022-02-14
End date
2023-12-22
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
Abstract
For many patients suffering from blood cancer, such as leukemia, who lack a related donor, a hematopoietic stem cell transplantation from a matching unrelated donor offers the best treatment and chance of survival. However, a substantial proportion of registered donors is unavailable to donate stem cells when invited to confirmatory typing (CT). At this decisive stage in the donation process, a matching patient has been found for the potential donor, and the donor is required to undertake medical checks to confirm genetic and medical suitability. Worldwide, unavailability ranges from about 25% to 50%. Reducing the unavailability rate can save lives, and is a key outcome of stem cell donation studies.
External Link(s)

Registration Citation

Citation
Haylock, Michael et al. 2023. "Improving the availability of stem cell donors - A letter and email intervention." AEA RCT Registry. July 13. https://doi.org/10.1257/rct.8938-2.0
Experimental Details

Interventions

Intervention(s)
In a natural field experiment, we randomly vary invitations to an existing activity of a major stem cell donor center, aimed at increasing the willingness of registered donors to be available at the confirmatory typing stage. The activity asks donors to fill out a health questionnaire, and to report any periods longer than three weeks that preclude donation. The experimental interventions comprise of an invitation, in form of a letter and an email, both with consistent framing, as well as the activity. We run two treatments and a baseline group. In the treatments, letters and emails are both framed so donors either belong to (i) a team of “quickly available donors,” or (ii) a team of “highly engaged” donors. The baseline group receives a letter (and email) with neither framing. The activity itself is the same for all invitees, and is voluntary. Not participating has no consequences for the donor. No one can participate in the activity who is not invited.
Intervention (Hidden)
In a natural field experiment (RCT), we randomly vary invitations to an existing activity of a major stem cell donor center, aimed at increasing the willingness of registered donors to be available at the confirmatory typing stage. The activity asks donors to fill out a health questionnaire, and to report any periods longer than three weeks that would preclude donation. The experimental interventions consist of an invitation by means of a physical letter followed by an email, both with the same framing and activity. We run two treatments and a baseline group. For internal evaluation purposes, the donor center runs another baseline group using the letter and email from prior to the intervention. In the treatments, letters and emails are both framed so that donors either belong to (intervention i) a team of “quickly available donors,” or (intervention ii) a team of “highly engaged” donors. The baseline group receives a letter (and email) with neither framing. The activity itself, completing a short medical survey and indicating unavailability dates, is the same for all invitees, and is voluntary. Not participating has no consequences for the donor, who will remain in the donor registry. No one can participate in the activity who is not invited.

As part of the intervention, we send the invitations to around 400,000 registered donors in the stem cell donor center. We evaluate the take-up rate (participation) in the activity, the frequency of reporting absences, and most importantly, whether a donor proceeds with confirmatory typing when called upon (primary outcome). The donor center is able to match administrative data on potential donors who are sent an invitation to participate in the activity. For instance, data includes information from when potential donors initially registered and data from the field experiment. All donor related data stays within the donor center.

This study can help answer the following primary research questions:
How does additional donor effort before a donation request affect subsequent donation availability?
How does donor identity (i.e. being an “engaged” or “quickly available” donor) matter for following through with donation, participating in the activity, and reporting absences?

Given the research questions, we will test for differences in outcomes between the three invitations sent out.

The trial end date is dependent on receiving 6,000 CT requests from the three treatment letters (based on our 400,000 invitations). When this number is reached, we will stop the trial. If this number is not reached by 5 years, the trial will also be stopped.

UPDATE:
Invitations to the experiment were stopped by the executive board of the donor center on June 22, 2022. Hence, data collection commenced after the first invitations were sent out and will be stopped either one and a half years after the last invitation was sent out (December 22, 2023) or after 150 CT requests per treatment arm have been collected (depending on what happens first).
Intervention Start Date
2022-02-14
Intervention End Date
2022-06-22

Primary Outcomes

Primary Outcomes (end points)
Our primary outcome variable is a potential donor’s availability at the confirmatory typing (CT) stage.
Primary Outcomes (explanation)
CT availability measures the donor’s availability (i.e., willingness to move forward) at the confirmatory typing stage to follow through with the stem cell donation process, after a matching patient needing a stem cell transplant has been identified, based on genetic characteristics (such as HLA loci, blood group, and immunity to cytomegolavirus). More specifically, CT availability includes going to a clinic for an extra medical screening, and filling out a health questionnaire.

Secondary Outcomes

Secondary Outcomes (end points)
Our secondary outcome variables include the take-up rate of the activities and unavailability reporting behavior.
Secondary Outcomes (explanation)
The take-up rate measures whether an invited registry member has actively agreed to take part in the activity. This measure will be evaluated continually.

Absence reporting behavior measures how often participants in each experimental group reported being absent.

Experimental Design

Experimental Design
In a natural field experiment, we randomly vary invitations to an existing activity of a major stem cell donor center, aimed at increasing the willingness of registered donors to be available at the confirmatory typing stage.
Experimental Design Details
In a natural field experiment, we randomly vary invitations to an existing activity of a major stem cell donor center, aimed at increasing the willingness of registered donors to be available at the confirmatory typing stage. The activity asks donors to fill out a health questionnaire, and to report any periods longer than three weeks that preclude donation. The experimental interventions comprise of an invitation, in form of a letter and an email, both with consistent framing, as well as the activity. We run two treatments and a baseline group. In the treatments, letters and emails are both framed so donors either belong to (i) a team of “quickly available donors,” or (ii) a team of “highly engaged” donors. The baseline group receives a letter (and email) with neither framing. The activity itself is the same for all invitees, and is voluntary. Not participating has no consequences for the donor. No one can participate in the activity who is not invited.
Randomization Method
For this activity, the donor center determined the frequencies of donor genotypes (for genes that are to date considered relevant for transplantation). For each genotype a certain number of donors are designated with a maximum allowed age. Thereby for more frequent genotypes the maximum age is set lower than for rare genotypes. The number of donors per genotype remains the same, but over the years people drop out of the desired age and so free spots are generated.

On a rolling basis an algorithm selects donors to fill up the free spots in the activity. For the intervention, the generation of a random number was implemented in the algorithm. Based on this number, the donor randomly receives a specific treatment for the intervention.
Randomization Unit
Individual (potential stem cell donor)
Was the treatment clustered?
No

Experiment Characteristics

Sample size: planned number of clusters
n/a
Sample size: planned number of observations
6,000 observations for primary outcome. Sample for analysis: We will send 133,333 invitations each year (comprising all experimental treatments), in 2022, and 133,333 in 2023, and 133,333 in 2024. In addition to our field experiment, the donor center will collect data on a control group of about 133,333 persons who are randomly not invited to the letter intervention, but share same characteristics as experimental subjects. Other data collected by the donor center: Additionally, the donor center will collect data on 133,333 invitations using the letter they used prior to the intervention, only for internal monitoring.
Sample size (or number of clusters) by treatment arms
2,000 from each experimental manipulation (plus ca. 2,000 from a control group (without invitation) constructed by the donor center).
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
For the experimental treatments, we plan to send around 400,000 invitations out over 4 years, which will in expectation lead to 6,000 CT requests in total. Estimated with past donor center data, there is a 1.5% probability of being requested within 2 years of receiving the letter. If we evaluate the results with a two-sided proportion test, and correct for multiple hypothesis testing over the two treatments and a control letter (giving alpha=0.025), we have a power of 0.8, and a minimum detectable effect size of 3.75pp (intention-to-treat), given a baseline availability rate of 80%. We also expect to add 2,000 CT requests to the data from the group that receives no letter in order to test for overall letter effects. The corresponding MDE in this case (comparing treatments to the control group that receives no letter) amounts to 4pp.
IRB

Institutional Review Boards (IRBs)

IRB Name
Ethics Committee of the Faculty of Economics and Social Sciences, University of Tuebingen
IRB Approval Date
2021-08-03
IRB Approval Number
A2.5.4-186_ns
IRB Name
Homewood Institutional Review Board, Johns Hopkins University
IRB Approval Date
2021-10-05
IRB Approval Number
HIRB00013790

Post-Trial

Post Trial Information

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Intervention

Is the intervention completed?
No
Data Collection Complete
Data Publication

Data Publication

Is public data available?
No

Program Files

Program Files
Reports, Papers & Other Materials

Relevant Paper(s)

Reports & Other Materials