Simple donor message could expand stem cell transplant options

When a patient needs a stem cell transplant, finding a registered donor is only the first step. Some potential donors drop out before confirmatory typing, reducing the pool from which doctors can choose. Researchers from the University of Osaka and collaborators tested whether a small change in wording could help more donors continue. This study was published in the Journal of Economic Behavior & Organization.

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), the pre-donation test used to check whether a donor is suitable. Recruiting new donors is costly, so preventing dropout among people already registered is a major practical issue.

The team worked with the Japan Marrow Donor Program to conduct a randomized field experiment from September 2021 to February 2022. A total of 11,154 HLA match letters were assigned to four groups: standard letter only, a "matching difficulty" message, an "early coordination" message, or both messages. The analysis covered 11,049 coordinations involving donors living in Japan.

The matching difficulty message told donors that the number of registered donors compatible with one patient is limited. This raised the CT-reaching rate from 22.25% to 23.88%, a 1.63 percentage-point increase, or 7.3% in relative terms. The early coordination message did not significantly increase CT completion, and combining both messages weakened the effect, suggesting that simple information works best.

The effect is estimated to be equivalent to securing about 40,880 new donor registrations, offsetting roughly 40.9% of the projected five-year donor-pool decline of about 100,000 donors caused by the donation age limit. The finding offers a low-cost way to help doctors access a broader donor pool.

Without using money or pressure, one factual sentence can help donors' goodwill reach patients more reliably. We hope this evidence supports practical improvements in transplant coordination."

Professor Fumio Ohtake