A national proficiency scheme for human leucocyte antigen typing by next-generation sequencing

Background: Accurate human leucocyte antigen (HLA) typing is essential for solid organ transplantation (SOT) and hematopoietic stem cell transplantation (HSCT). Next-generation sequencing (NGS) is increasingly adopted by clinical laboratories performing HLA typing. To ensure reliable NGS-based HLA typing throughout China, a HLA-NGS proficiency testing (PT) scheme was set up. Methods: A panel of 10 DNA reference materials for 11 HLA loci were distributed to 24 participants. They were asked to submit NGS typing results for at least six loci including HLA-A, HLA-B, HLA-C, HLA-DRB1, HLA-DQB1, and HLA-DPB1. Information regarding individual laboratory's sample preparation method, NGS platform, and genotyping software was also collected. Results: Thirteen participants correctly identified HLA alleles in all samples. The total concordance rate for all HLA alleles typed was 99.2% (3390/3420). The overall discordance was 0.2% (3/1440) for Class I, and 1.4% (27/1980) for Class II loci. Further investigation of the typing mistakes pointed to poor sequencing coverage and wrong allele calls. The errors identified reflect the deficient aspect of NGS in HLA typing, which may have implications for quality improvement for relevant laboratories. Conclusions: The results of this PT underscore the necessity of regular participation in external quality assessment for clinical laboratories that perform HLA-NGS typing.