HLA Matching Finds Suitable Donors for Majority of Hematopoietic Stem Cell Transplant Candidates
A study reported by Gragert et al in The New England Journal of Medicine indicates that most candidates for hematopoietic stem cell transplantation in the United States will have a suitable adult donor on the basis of HLA matching, although many will not have optimal donors. Few will have optimal cord blood matching, but most will have units with one or two HLA mismatches.
The study used HLA data from the National Marrow Donor Program (NMDP) donor and cord-blood unit registry to predict the likelihood of identifying a suitable adult donor or cord-blood unit according to 21 racial/ethnic groups. Predictive models incorporated degree of HLA matching, adult donor availability, and cord-blood unit cell dose.
HLA-Matched Adult Donors
The models indicated that most candidates for hematopoietic stem cell transplantation will have an HLA-matched or minimally mismatched adult donor. Likelihoods of an adult donor with an 8/8 HLA match ranged from 75% for white Europeans, 52% for Native North Americans, and 49% for Native South or Central Americans to 19% for black Caribbean patients, 18% for Africans, and 16% for Black South or Central Americans. Likelihoods of an adult donor with a ≥ 7/8 HLA match were much higher, ranging from 97% for white Europeans to 71% for Africans.
Cord-Blood Units
The greatest likelihoods for identifying a cord-blood unit with a 6/6 HLA match were 17% for white Europeans ≥ 20 years of age and 38% for white Europeans < 20 years of age. Likelihoods for all racial/ethnic groups for identifying cord-blood units with a ≥ 5/6 HLA match ranged from 23% to 53% for patients aged ≥ 20 years and from 56% to 80% for patients aged < 20 years. Likelihoods for a ≥ 4/6 HLA match ranged from 81% to 96% for patients aged ≥ 20 years and from 95% to 99% for those aged < 20 years.
The investigators concluded: “Most patients likely to benefit from [hematopoietic stem cell transplantation] will have a donor. Public investment in donor recruitment and cord-blood banks has expanded access to [hematopoietic stem cell transplantation].”
Loren Gragert BS, BA, is the corresponding author for The New England Journal of Medicine article.
The study was funded by the Department of the Navy and the Department of Health and Human Services. For full disclosures of the study authors, visit www.nejm.org.
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