Analysis of HLA Allelic and Haplotypic Frequencies in a Cohort of Bone Marrow Donors in Catalonia: Impact of Next-Generation Sequencing on Donor Registry Quality

Abstract

In haematopoietic stem cell transplantation (HSCT), the volunteer unrelated donor (VUD) has become the most common strategy in Europe, as improved outcomes are achieved through HLA compatibility at allelic-level resolution. In this context, the implementation of next-generation sequencing (NGS) in histocompatibility typing laboratories has significantly enhanced the quality of bone marrow registries, enabling a high level of resolution at a lower cost and improved performance. In this study, we analyse a large cohort of 21,787 bone marrow donors in Catalonia and present the observed HLA allelic and haplotypic frequencies, along with their linkage disequilibria. HLA-A, -B, -C, -E and -G were genotyped at full resolution, while -DRB1, -DQB1, -DQA1, -DPA1 and -DPB1 were genotyped at high resolution. We identified 236 new officially named HLA alleles, both coding and non-coding regions. This study highlights that the implementation of high-throughput HLA typing has led to an increase in the number of registered donors and an improvement in quality, which has been reflected in a rise in the number of effective donors.