The right approach increases willingness to donate stem cells

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Collection of stem cells at the DKMS Collection Center in Cologne.
Collection of stem cells at the DKMS Collection Center in Cologne.

Every year, more than 20,000 people in Germany die from blood cancer. In children, blood cancer is even the most common type of cancer. Donations of stem cells from bone marrow or blood increase the chance of survival for people suffering from leukemia or other forms of blood cancer. However, it can take years between the registration of those willing to donate and their actual donation. Many volunteers are reluctant to donate when the stem cells are actually collected. An international team of researchers has now shown that renewed contact between registration and donation significantly increases the availability of donors. This effect is strongest when a blood sample is also requested.

The results have been published in the American Journal of Health Economics and provide important information for donor registries worldwide to improve their placement rates. Researchers from the University of Tübingen, Johns Hopkins University, the University of Technology Sydney, the Universities of Cologne and Essen-Duisburg as well as employees of the world’s largest donor database DKMS were involved in the study.

DKMS has a register of more than 12 million willing donors in the USA, Germany, Poland, the UK, South Africa, Chile and India. The researchers were able to analyze a data set of 91,670 willing donors from 2013 to 2018 whose biological characteristics matched those of a patient with blood cancer. They were then asked again about their willingness to donate stem cells as part of the confirmatory typing process, one of the key steps on the path to stem cell donation. DKMS contacted some of these people with various letters asking for additional data or blood samples. For example, recipients were asked to update information on previous illnesses or to note stays abroad and pregnancies that would have prevented a donation in an emergency. A subgroup was also asked to provide an additional blood sample for retyping in order to complete the genetic information. The other registered persons were not contacted again by DKMS for cost reasons and formed the control group for the study.

When a blood sample was requested in addition to the new letter, the number of registrants who were subsequently reluctant to donate fell by 37 percent. It is quite astonishing that we were able to identify such positive effects despite the additional effort involved in taking a blood sample. The donors are reminded of their ability to help by being contacted again and they probably feel more motivated as a result," says Professor Patrick Kampkötter from the Department of Economics at the University of Tübingen, explaining the results of the study.

"At DKMS, we knew that every additional contact with potential donors during the study period was important - but not that the increase in their availability was so much higher. Now this finding has been scientifically proven and evaluated, every donor registry can consider whether the costs of the additional effort involved in making contact again are in proportion to the effect," says Alexander Schmidt, Chief Medical Officer at DMKS.

Unlike a simple blood donation, a stem cell donation requires a "genetic twin" of donor and recipient to be found, in which twelve specific genes must match - otherwise the risk of a fatal immune response in the recipient is too great. Once this "genetic twin" has been found - if necessary after a worldwide search - and the donor drops out or is unavailable due to travel or pregnancy, the database loses valuable time in the search for another match. In the meantime, the chance of survival for patients with blood cancer who urgently need suitable stem cells for their therapy is decreasing. Being able to differentiate between the availability of donors in advance and increase their motivation therefore saves a donor register valuable time.

A common ethnic origin between donors and recipients also increases the probability of a genetic match. Statistically, the willingness to donate differs considerably between ethnic groups. In Germany, 75 percent of those registered with DKMS are willing to donate in an emergency, whereas in the USA only half are willing on average, and among some ethnic groups such as African-Americans or Hispanics only around 30 percent. "Improving the availability of stem cell donors is therefore of great medical and economic benefit to donor registries in countries such as the USA," says Mario Macis from Johns Hopkins University in Baltimore, Maryland, USA.


Michael Haylock, Patrick Kampkötter, Mario Macis, Jürgen Sauter, Susanne Seitz, Robert Slonim, Daniel Wiesen, Alexander H. Schmidt: Reducing Registry Members’ Attrition When Invited to Donate: Evidence From a Large Stem Cell Registry. American Journal of Health Economics.