Michael Haylock (University of Tübingen)

Understanding how to effectively cope with the availability of hematopoietic stem cell donors for confirmatory typing is important for stem cell donor registries and researchers alike. The uncertain time horizon from enrolling to actually becoming a donor is a particular challenge for registries. This paper evaluates the impact of a set of initiatives aimed at improving stem cell collections and CT availability of donors at DKMS, one of the largest registries worldwide.

A subset of registered donors receive invitation letters to initiatives prior to an actual request for a stem cell donation. Donor ``retyping'' initiatives asked for a blood sample and more medical information, with a specific patient in the background (``patient-centered'' retyping) or without. Donor ``retention'' initiatives asked for notification of longer absence from home, as a commitment device. Exploiting the near-random allocation of initiatives to donors based on observable medical characteristics, we find evidence that the initiatives enhance the availability of donors when they receive an actual request. Patient-centered retyping initiatives are associated with a 5.9 percentage-point increase in availability on average, 5.0 percentage points higher than non-patient related initiatives. Retention initiatives with a ``team'' framing increase availability by 1.2 percentage points, which is 2.0 percentage points larger than a neutral frame that has a marginally negative impact. Participation in any of the initiatives predicts subsequent donor availability, whereas non-participation predicts unavailability only in retention initiatives. We discuss the implications of our findings for stem-cell donor registries.