The search for a suitable human leukocyte antigen (HLA)-matched unrelated adult stem cell donor (URD) or umbilical cord blood unit (UCB) is a complex process. The National Marrow Donor Program (NMDP) developed a search algorithm known as HapLogic, which is currently provided within the NMDP Traxis application. The HapLogic algorithm has been in use since 2006 and has advanced URD/UCB HLA-matching technology. The algorithm has been shown to have high predictive accuracy, which can streamline URD/UCB selection and drive efficiencies in the search process to the benefit of the stem cell transplantation community. Here, we describe the fundamental components of the NMDP matching algorithm, output, validation, and future directions.
The National Marrow Donor Program's Be The Match Registry(®) facilitates the worldwide utilization of unrelated donor (URD) grafts for patients in need of a hematopoietic cell transplantation. In this study, we estimate the URD match rate for patients of White (WH), Hispanic (HIS), Asian/Pacific Islander (API), and African American/Black (AFA) race and ethnic groups. We chose 1344 URD at random as "pseudo-patients" (PP) to estimate the likelihood of finding an 8/8 or 10/10 high-resolution HLA-A,-B,-C,-DRB1 (and -DQB1) matched URD. Searches were conducted in the Be The Match Registry database for each PP at 2 time points: 2009 and 2012. URD who were a potential match for a PP by low/intermediate resolution were HLA typed by sequence-based typing to resolve the matching status. The 8/8 match rate for WH PP improved from 68% in 2009 to 72% in 2012. Corresponding match rates were 41% to 44% for HIS, 44% to 46% for API, and 27% to 30% for AFA, for 2009 and 2012, respectively. The 2012 10/10 match rates were 67% for WH, 38% for HIS, 41% for API, and 23% for AFA. These results provide baseline 8/8 and 10/10 match rate estimates by race for patients seeking an URD.
Estimation of the National Marrow Donor Program's Be The Match Registry 8/8 (HLA-A, -B, -C, and -DRB1) high-resolution (HR) unrelated donor (URD) match rate was determined in a prior study for each of the 4 most frequent patient race/ethnic groups in the United States: white (WH), Hispanic (HIS), Asian/Pacific Islander (API), and African American (AFA). For patients without an 8/8 HLA-matched URD, a 7/8 match, with a single allele or antigen mismatch, is often accepted by many transplant centers. A follow-up study was designed to determine the 7/8 or better match rate among the 4 major race/ethnic groups, using the same study cohort. Of previously HR tested URDs in the Be The Match Registry, 1344 were randomly selected and treated as pseudo-patients where HR testing was performed to identify a 7/8-matched URD; 98% of WH and over 80% of non-WH race/ethnic groups (HIS, API, and AFA) had at least a 7/8 match identified. In most cases after first testing to identify an 8/8-matched URD, a 7/8-matched URD was identified after typing just 1 URD. Extending criteria to identify a 9/10 match (included HLA-DQB1) showed the 9/10 absolute match rate decreased between 14% and 21% from the 7/8 match rate for the non-WH groups. This study provides a baseline 7/8 and 9/10 or better HLA match rate that can be further supplemented using the additional worldwide URD inventory. URD match rate information can equip centers in clinical planning and the education of patients seeking a life-saving therapy.
Therefore, the HLA HFD that informs the HapLogic matching algorithm is thorough as UPH patient searches were infrequent. Since such patients are highly unlikely to have a fully 10/10 matched URD identified, this study supports the identification of alternative stem cell sources including cord blood or a mismatched URD early in the search process.
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