By Palesa Mokomele, Head of Community Engagement and Communication at DKMS Africa
For years, Black South African patients with blood cancer or blood disorders searching for a stem cell donor were told the odds were not in their favour. Their ancestry, the thinking went, carried too much genetic diversity for a donor search to reliably succeed. New research published in Blood Global Hematology says otherwise. The genetics, it turns out, are not the problem. What stands between many Black patients and a lifesaving transplant is the registry, and who is on it.
A study of nearly 57 000 South Africans mapped the HLA profiles of all four of the country’s population groups to calculate each community’s real odds of finding a match. HLA markers are what doctors use to determine whether a donor’s stem cells are compatible with a patient’s. In a same-community registry of a million donors, a Black South African patient’s probability of finding a full match is 80%. For a White patient, the figure is 81%.
The Registry Gap
The registry does not reflect the country it serves, and that gap is costing lives. South Africa is approximately 81% Black African and 7% White. In the study cohort, Black South Africans made up roughly 37% of donors and White South Africans 45%. Donor drives went where they were easiest to run, and the communities hardest to reach were left out.
The findings revealed large areas of the country where Black African donor representation is almost absent. Entire provinces contribute too few donors for researchers to meaningfully analyse matching patterns. Of the fifteen subpopulations large enough to analyse by language and province, seven were White communities.
The two least genetically diverse groups in the study were Afrikaans-speaking White people in Mpumalanga and isiXhosa-speaking Black Africans in the Western Cape. Because people in these communities are more genetically similar to one another, each new donor has a better chance of matching someone who needs them.
The registry is at least heading in the right direction. Fifty-six percent of new registrations come from people of colour. But it holds just 200,000 donors across all population groups, and the destination is a registry of a million Black African donors alone.
The Human Cost
Consider what that means for a patient like Sbahle, a six-year-old girl diagnosed with aplastic anaemia before she could pronounce the word. She has spent four years, most of her life, waiting for a donor. She is stable, back at school, and still without a match. Not long ago, a family in her position would have been told the odds were against them, and there was little to be done. We know better now.
For a patient still waiting, the donor who could save them may already be out there, alive, healthy, and simply not on the registry.
Not Everyone’s Odds Are the Same
The progress is not uniform. Coloured and Indian/Asian South Africans face a harder search: their greater genetic diversity means common profiles cover far less of the group, around 21% for Coloured patients, and full matches are rarer.
The outlook is not bleak. In a registry of 100,000 donors from their own group, a Coloured patient has roughly a 51% chance of a nine-out-of-ten match and 92% of an eight-out-of-ten. Advances in transplant medicine are also shifting what a near-match means in practice. Recent research has shown that post-transplantation cyclophosphamide, a drug used to prevent graft-versus-host disease, significantly reduces the impact of donor mismatches, to the point where a single mismatch may be clinically negligible. For Coloured and Indian/Asian patients who cannot find a full match, that development changes the calculation considerably.
From Research to Reality
This research also points to where investment should go. The biggest gains will not come from a new algorithm or a better search tool. They will come from signing up donors in the communities the registry has missed. That is slow, expensive, deeply unfashionable work, and it is the thing that actually gets a patient to a transplant.
Recruitment has to reach into Limpopo, KwaZulu-Natal, the Eastern Cape, the Northern Cape and the rural areas with no donor base at all, and it has to be permanent, not a run of once-off drives.
Science has now answered one of the biggest questions in stem cell transplantation: Black South Africans are not inherently harder to match. The challenge is building a registry that reflects the country itself. Every new donor brings that goal, and patients like Sbahle, closer.
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