When a patient requires a stem cell transplant, finding a registered donor is only the first step. Some potential donors drop out before confirmation typing, reducing the number of candidates available to physicians from. Researchers at Osaka University and their collaborators tested whether a small change in wording could encourage more donors to stick around. This study Economic Behavior and Organization Journal.
Hematopoietic stem cell transplantation is an important treatment for leukemia and other blood cancers, but donor availability remains a challenge worldwide. In Japan, many coordination processes stop before confirmatory typing (CT), a pre-donation test used to confirm whether a donor is suitable. Recruiting new donors is expensive, so preventing those who have already registered from dropping out is a major practical challenge.
The research team collaborated with the Japan Bone Marrow Donor Program to conduct a randomized field experiment from September 2021 to February 2022. A total of 11,154 HLA-matched letters were assigned to four groups: standard letters only, “difficult to match” messages, “early adjustment” messages, or both messages. The analysis included 11,049 adjustments involving donors residing in Japan.
The Match Difficulty message informed donors that there was a limited number of registered donors who could accommodate a single patient. This increased the CT reach rate from 22.25% to 23.88%, a relative increase of 1.63 percentage points or 7.3%. Early conditioning messages did not significantly improve CT completion rates, and combining both messages weakened the effect, suggesting that simple information was most effective.
This effect is estimated to be equivalent to securing approximately 40,880 new donor registrations, offsetting approximately 40.9% of the projected reduction in the donor pool of approximately 100,000 people over five years due to the donation age limit. This discovery provides a low-cost way for physicians to access a broader donor pool.
Without money or pressure, a fact-based statement can help ensure that the donor’s good intentions reach the patient. We hope that this evidence supports practical improvements in transplant coordination. ”
Professor Fumio Otake
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DOI: 10.1016/j.jebo.2026.107666
