Interventions to improve stem cell donor availability

Last registered on November 17, 2025
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Pre-Trial

Trial Information

General Information

Title
Interventions to improve stem cell donor availability
RCT ID
AEARCTR-0016801
Initial registration date
November 10, 2025

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
November 17, 2025, 6:59 AM EST

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

Locations

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Primary Investigator

Name
Yero Samuel Ndiaye
Affiliation
University of Cologne
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Other Primary Investigator(s)

PI Name
Daniel Wiesen
PI Affiliation
University of Cologne
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PI Name
Patrick Kampkoetter
PI Affiliation
University of Tuebingen
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PI Name
Axel Ockenfels
PI Affiliation
University of Cologne and MPI
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PI Name
Till Stange
PI Affiliation
University of Cologne
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Additional Trial Information

Status
In development
Start date
2025-11-11
End date
2026-06-30
Keywords
Behavior, Health
Additional Keywords
JEL code(s)
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
Abstract
This study tests whether behavioral narrative interventions and belief corrections increase stem cell donors' availability for confirmatory typing (CT). The research uses a factorial design testing 21 narrative treatments × 2 belief correction conditions + 1 video condition on stated CT availability to identify optimal intervention combinations. Narratives target altruism, cost reduction, and intention-action gaps, while belief correction addresses misconceptions about stem cell extraction methods. Primary outcomes are stated CT availability.
External Link(s)

Registration Citation

Citation
Kampkoetter, Patrick et al. 2025. "Interventions to improve stem cell donor availability." AEA RCT Registry. November 17. https://doi.org/10.1257/rct.16801-1.0
Sponsors & Partners
Experimental Details

Interventions

Intervention(s)
Behavioral narrative interventions, belief correction about stem cell extraction methods, and one video treatment designed to increase stem cell donor availability for confirmatory typing.
Intervention Start Date
2025-11-11
Intervention End Date
2026-06-30

Primary Outcomes

Primary Outcomes (end points)
Stated CT availability – willingness to donate if contacted
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Survey completion rates (1), knowledge about extraction methods (2), contact information updates (3), absence reporting (4), actual CT availability (5)
Secondary Outcomes (explanation)
These measure intervention engagement, intermediate behavioral changes, and knowledge acquisition that may predict actual donation availability and follow-through.

Experimental Design

Experimental Design
This RCT tests whether behavioral narrative interventions and belief corrections increase stem cell donors' availability for confirmatory typing (CT). The research uses a factorial design testing 21 narrative treatments × 2 belief correction conditions + 1 video condition on stated CT availability to identify optimal intervention combinations. Narratives target altruism, cost reduction, and intention-action gaps, while belief correction addresses misconceptions about stem cell extraction methods. Primary outcomes are stated CT availability.
Experimental Design Details
Not available
Randomization Method
Computer-generated random assignment
Randomization Unit
Individual donor level
Was the treatment clustered?
No

Experiment Characteristics

Sample size: planned number of clusters
Not applicable
Sample size: planned number of observations
minimum of 90,000 completed surveys (minimum of 2,000 per condition × 45 conditions)
Sample size (or number of clusters) by treatment arms
2,000 per factorial condition, 4,000 per narrative (with/without belief correction), 88,000 per belief correction treatment (pooled across all narratives), 2,000 for video treatment (all minimums respectively)
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
Assumed baseline: 90% state they are available for CT Assumed narrative effects: 1-5 percentage points Assumed belief correction effect: 2 percentage points Power achieved with n=2,000 per condition: Individual narratives: 91% power (average 19 of 21 detected, BH-adjusted) Belief correction main effect: >99% power Video effect: >99% power Joint test (any narrative works): >99% power Heterogeneity test (narratives differ): >99% power Minimum Detectable Effect (MDE) at 80% power: approximately 1.5 percentage points for individual narratives
Supporting Documents and Materials

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IRB

Institutional Review Boards (IRBs)

IRB Name
RESEARCH ETHICS REVIEW FACULTY OF MANAGEMENT, ECONOMICS, AND SOCIAL SCIENCES UNIVERSITY OF COLOGNE
IRB Approval Date
2025-10-08
IRB Approval Number
240124YN
Analysis Plan