Reducing the unavailability of stem cell donors

Michael Helk, Patrick Campcott, Mario Maxis, Robert Slonem, Daniel Wiesen 02 July 2022

For patients suffering from leukemia or other blood diseases, a hematopoietic stem cell transplant from a combined, unrelated donor often offers the best chance of survival. However, the unavailability of potential stem cell donors who have already joined the donor registry is an important challenge, which hinders the donation process and, consequently, reduces the chances of survival of many patients (e.g. Gratwohl et al. 2015).

Unlike other medical donations, a stem cell donation is a multi-stage process (e.g. Bergstrom et al. 2009). First, potential donors sign up for a stem cell donor registry and provide the first aid information used to determine who they can donate to. Second, registry members can be contacted weeks, months, or even years later if they are a potential biological match for the patient. If they are contacted, they will receive a request for ‘confirmatory typing’ from a transplant center to determine if they are actually genetically and medically suitable for hematopoietic stem cell transplantation. This mandatory confirmatory typing step is the determining point for deciding whether to follow through on a grant on behalf of a potential donor. Third, replacement occurs if they are a match and agree to donate.

After registration, potential donors do not make a mandatory commitment to donate stem cells at some point in the future. Therefore, the donation process is characterized by uncertainty about when the grant opportunity will be implemented. This unique setup exacerbates commitment issues for donors, as it differs from other medical contributions such as blood donation, which occurs with commitment (e.g. Lacetera and Macis 2008, Lacetera et al. 2012).

The tendency of donors not to follow their non-binding commitments (e.g. attrition) at the confirmation-typing stage is a significant problem for stem cell donor registries around the world. In Western countries, losses range from 23% to 56% (e.g. Lown et al. 2014, Anthias et al. 2020). Attrition delays the process of finding a suitable donor and increases the waiting time for many replacements, which can negatively affect a patient’s survival rate. Thus, understanding how the initiative to collect additional information from donors affects the likelihood of being followed through the grant process is crucial for donor registry managers.

In our study (Haylock et al. 2022), we analyzed a set of initiatives implemented by DKMS Germany, a leading stem cell donor registry with more than 11 million registered donors, in an effort to address this challenge. Initiatives target individuals who have signed up to the donor registry but have not yet been selected for confirmed typing and are likely to affect donor commitments. Participating in the initiative involves some costly steps. For example, registry members are asked to send biological material through buccal swabs, draw blood for genetic retyping, and / or report long absence dates in advance.

Specifically, we examine DKMS’s three initiatives: ‘expected’, which prompts potential donors to retype; ‘Status update’, which asks potential donors to report the date of unavailability (such as due to pregnancy or being abroad); And ‘Status Update-Blood’, which requests to be re-typed through a blood draw and asks donors to report their unavailability. Although initiatives vary depending on the efforts of donors, they all aim to reduce delays at the guaranteed typing stage.

We analyzed 91,479 requests for confirmatory typing issued by potential donors registered in DKMS Germany between 2013 and 2018. Our data contains donor-related and registry-related information that DKMS registry members use to determine if they are invited to participate in the initiative.

We first examined whether invitations affected registry members’ desire to be available for certain typing, regardless of whether they accepted the invitation. We do this by comparing the percentage of unavailable people between those who were invited and those who were not invited at each initiative. Given how DKMS chose to invite individuals to the initiative, and provided a lot of information about each person, we were able to compare people who were invited to an initiative to other identical individuals who were not invited.

We further tested that groups of individuals who chose to participate in the initiative were less likely to be unavailable than members of the DKMS registry who did not receive an invitation to the initiative. This group of initiative participants can no longer be considered identical to those who have not been invited, as they have indicated to DKMS by joining an initiative that they are more motivated to help. And here’s the point: these initiatives not only provide DKMS with useful information from updated health and availability information, but also help DKMS identify more motivated registry members.

Invitation Invitation Effect (‘Direct’ Effect)

Our analyzes show that the unavailability of donors at the unconditional, confirmatory typing stage for their actual participation in initiatives was significantly lower for potential donors who were invited to an initiative than non-invitees. Figure 1 shows the average level of unavailability for each venture and for those who were not invited to the venture: on average, 22.9% of registry members who were not invited to a venture were unavailable when asked to follow up with confirmation typing, where only ‘status update-blood’ 17.6 of the registry members invited to participate in are unavailable.

Figure 1 Unavailability of potential donors for confirmatory typing through the initiative, unconditional participation in an initiative (sample average)

Formula: Haylock et al. (2022)

In our official statistical analysis, we need to ‘adjust’ to the differences between the registry members who did not receive and did not receive the invitation to the initiative. Following this adjustment, our statistical analyzes indicate that the availability of invited donors to the initiative, including rewriting (status update-blood and potential), was 3.2 and 2.5 percentage points (pp) higher than those who were not invited (both one-percent). Level significant). Since for members who did not receive invitations the unavailability at the confirmation typing stage was 22.9%, the lower unavailability of members who received ‘Status Update-Blood’ and ‘Expected’ invitations decreased by 14.0% (3.2 / 22.9) and 10.9% (2.5 / 22.9) respectively. However, asking for additional information without re-typing (status update) did not significantly affect donor availability.

Participants in the initiative are more likely to follow (‘predictive’ effect)

Ensuring participation in an initiative strongly reduces donor unavailability at the typing stage. For all initiatives, Figure 2 shows that, on average, donors who choose to participate are significantly less likely to be unavailable for certain typing than non-participants.

Figure 2 Unavailability of potential donors for enterprise confirmation typing, conditional on participation in an initiative (sample average)

Formula: Haylock et al. (2022)

After resolving the differences between participants and non-participants, our analyzes indicate that the re-typing initiative (potential) and the re-typing plus blood-draw initiative (status update-blood) led to 4.3 and 8.2 percentage points higher availability, respectively (both). Highly statistically (significant) compared to registry members who did not receive an invitation to the initiative. Participating in the ‘Status Update’ initiative increased availability by 3.8 percentage points, but this estimated impact was not statistically significant. Thus, those who did not receive an invitation to an initiative were 16.6% (3.8 / 22.9) and 35.8% (8.2 / 22.9) less likely to be unavailable than those who did not receive an invitation to an initiative, indicating a significant improvement in finding stem cell donors faster.

Our research on the effects of initiatives managed by stem cell donor registries provides practical insights for managing these registries. In particular, the link between the unavailability of confirmatory typing and the participation of registered donors in an initiative is positive and large-scale. This represents a valuable opportunity for registries to employ such initiatives to find available donors more quickly and successfully.

In addition, participating in a donor’s decision requires updating information on an initiative that provides practical information in the registry that would not otherwise be available. Depending on the time it takes for participating donors to report future absences, for example, the registry may avoid wasting time trying to reach these donors when it is not available. This makes the donation process more efficient (i.e. significantly faster). As a result, donor registries should be given the opportunity to make such information available to the Search Coordinator and the Transplant Center. These insights can help managers of donor registries inspire potential donors to follow through with their donations.


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