Aim: To provide 2 field high resolution HLA typing for deceased donors (DD).
Method: HLA DD typing was performed using standard RT-PCR and GenDx Turbo Next Generation Sequencing. Here we report the implementation of NGS for DD typing at SWID. From Nov. 1 '23 through April 30 '24 a total of 140 DD typings were performed by both NGS and RTPCR. TAT's were monitored for NGS as well as discrepancies in typing, resolution of ambiguities and new alleles.
Results: The average TAT from DNA extraction to reporting results using NGS is 4.5 hr. NGS resolved ambiguities seen in RTPCR which were impactful particularly in the Class II region. For ex. NGS typing called a DRB1*04:08, 04:11 outright whereas the RTPCR gave many DR4 ambiguities that had clinical impact. Although there was good correlation between RTPCR and NGS there were clinically relevant discrepancies. The most significant ones involved RT-PCR assigning HLA proteins whereas NGS called null alleles. These assignments unnecessarily restricted access for patients who had listed those antigens as avoids. NGS has also identified at least two new alleles - one at B locus and one at DPA.
Conclusion: With the change in the CMS final rule allowing VXM in lieu of a physical crossmatch accurate high resolution HLA typing of deceased donors (DD) has become increasingly important. Currently the most common method for HLA DD typing is RT-PCR which does not provide hi res results. The constraint for onboarding next generation sequencing (NGS) for deceased donors has been the length of time it takes to perform the assay. With the advent of newer techniques TAT is no longer an issue. The 2 field hi res data provided by Turbo NGS at SWID has allowed the HLA and clinical team to better assess offers for highly sensitized patients particularly those who have allele level antibodies and thus provided appropriate donor selection for this cohort of patients. Furthermore, having high res typing may speed up the allocation process in some scenarios where crossmatches are required to assess donor compatibility. Validation and staff training was quick as the lab was already routinely performing NGS. This technology is easy to integrate into the DD workflow and although it takes a little longer than standard RTPCR the increased level of resolution is worth pursuing as a community. Currently reporting is at the serological equivalent level but this will change when NGS becomes adopted by UNOS.
