Red cell genotyping precision medicine: a conference summary

Probabilistic mathematical modelling to predict the red cell phenotyped donor panel size

In the last decade, Australia has experienced an overall decline in red cell demand, but there has been an increased need for phenotyped matched red cells. Lifeblood and mathematicians from Queensland universities have developed a probabilistic model to determine the percentage of the donor panel that would need extended antigen typing to meet this increasing demand, and an estimated timeline to achieve the optimum required phenotyped (genotyped) panel. Mathematical modelling, based on Multinomial distributions, was used to provide guidance on the percentage of typed donor panel needed, based on recent historical blood request data and the current donor panel size. Only antigen combinations determined to be uncommon, but not rare, were considered. Simulations were run to attain at least 95% success percentage. Modelling predicted a target of 38% of the donor panel, or 205,000 donors, would need to be genotyped to meet the current demand. If 5% of weekly returning donors were genotyped, this target would be reached within 12 years. For phenotyping, 35% or 188,000 donors would need to be phenotyped to meet Lifeblood’s demand. With the current level of testing, this would take eight years but could be performed within three years if testing was increased to 9% of weekly returning donors. An additional 26,140 returning donors need to be phenotyped annually to maintain this panel. This mathematical model will inform business decisions and assist Lifeblood in determining the level of investment required to meet the desired timeline to achieve the optimum donor panel size.

DEL in China: the D antigen among serologic RhD-negative individuals

BACKGROUND

Providing RhD-negative red cell transfusions is a challenge in East Asia, represented by China, Korea, and Japan, where the frequency of RhD-negative is the lowest in the world.

FINDINGS

Among 56 ethnic groups in China, the RhD-negative frequency in Han, the prevalent ethnicity, is 0.5% or less, similar to most other ethnic groups. The Uyghur ethnic group has the highest reported RhD-negative frequency of up to 4.7%, as compared to 13.9% in the US. However, an estimated 7.15 million RhD-negative people live in China. The RhD-negative phenotype typically results from a loss of the entire RHD gene, causing the lack of the RhD protein and D antigen. The DEL phenotype carries a low amount of the D antigen and types as RhD-negative in routine serology. The DEL prevalence in RhD-negative individuals averages 23.3% in the Han, 17% in the Hui and 2.4% in the Uyghur ethnicities. The Asian type DEL, also known as RHD*DEL1 and RHD:c.1227G > A allele, is by far the most prevalent among the 13 DEL alleles observed in China.

CONCLUSION

The purpose of this review is to summarize the data on DEL and to provide a basis for practical strategy decisions in managing patients and donors with DEL alleles in East Asia using molecular assays.

The efficacy of ethnic specific blood groups genotyping for routine donor investigation and rare donor identification in Taiwan

BACKGROUND

Large-scale single nucleotide variation (SNV)-based blood group genotyping assays have been made available for over a decade. Due to differences in ethnic groups, there is much diversity in clinically important blood group antigens and genetic variants. Here, we developed a robust matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF)-based blood group genotyping method on MassARRAY system.

STUDY DESIGN AND METHODS

A total of 1428 donors were enrolled into three groups: (a) reagent red cell donors; (b) rare donor or common antigen-negative donors; and (c) group O, R₁ R₁ /R₂ R₂ donors. Forty-two SNVs were designed for determining nine blood groups, with X/Y chromosome in two multiplex reactions, on MassARRAY 96-well format system. Further targeted sequence analyses were performed by Sanger sequencing.

RESULTS

WHO reference reagent (NIBSC code: 11/214) was tested for concordance with the provided genotype results. Among the donors, concordance rate was over 99%. Alleles of important phenotypes such as Mi(a+), Di(a+), and Asian-type DEL and alleles of rare blood groups such as Fy(a-), Jk(a-b-) and s- were screened. Three types of discrepancies were found. Serologically, the 'N' antigen was expressed on genetically MM with GYP*Mur red blood cells and caused genuine discrepancies (9.5%). Genetically, allele dropout (ADO) was caused by rare SNV in the primer for Ss genotype (2.1%) and partial insertion of RHD genes (0.9%) led to difficulties in predicting phenotypes.

CONCLUSION

Hemo panel module and MassARRAY System in 96-well format showed good performance in terms of large-scale blood group genotyping and phenotype predictions. Implementation of this method is effective for routine blood group genotype screening of donors.

Red Cell Transfusions in the Genomics Era

Red cell genotyping has become widely available and now contributes to support transfusion of patients with hematologic diseases. This technology has facilitated the immunohematologic approach to antibody prevention, detection and identification. Donors, particularly rare donors, are most efficiently screened and identified by red cell genotyping. In transfused patients with challenging serologic reactivity, antibodies are more reliably identified when molecular typing information is available. Red cell genotyping of both donors and patients augments the selection of blood components. This technology, serving at the core of a real-time database inventory, is resulting in blood supply efficiencies. However, there is limited published evidence on the extent to which red cell genotyping has translated into improved clinical outcomes. Red cell alloimmunized patients may benefit the most in enhanced safety. For patients with antibodies to high-prevalence antigens, other than Rh, blood centers realized supply-chain efficiencies in the past decade. Prospective clinical trials and cost-effectiveness studies would contribute to further clarifying the optimal role of molecular testing in providing transfusion support for patients with hematologic diseases.

The role of genomics in transfusion medicine

PURPOSE OF REVIEW

To summarize recent advances in red blood cell (RBC) blood group genotyping, with an emphasis on advances in the use of NGS next generation sequencing (NGS) to detect clinically relevant blood group gene variation.

RECENT FINDINGS

Genetic information is useful in predicting RBC blood group antigen expression in several clinical contexts, particularly, for patients at high-risk for allosensitization, such as multiple transfused patients. Blood group antigen expression is directed by DNA variants affecting multiply genes. With over 300 known antigens, NGS offers the attractive prospect of comprehensive blood group genotyping. Recent studies from several groups show that NGS reliably detects blood group gene single nucleotide variants (SNVs) with good correlation with other genetic methods and serology. Additionally, new custom NGS methods accurately detect complex DNA variants, including hybrid RH alleles. Thus, recent work shows that NGS detects known and novel blood group gene variants in patients, solves challenging clinical cases, and detects relevant blood group variation in donors.

SUMMARY

New work shows that NGS is particularly robust in identifying SNVs in blood group genes, whereas custom genomic tools can be used to identify known and novel complex structural variants, including in the RH system.

Developments beyond blood group serology in the genomics era

Blood group serology and single nucleotide polymorphism-based genotyping platforms are accurate but do not provide a comprehensive cover for all 36 blood group systems and do not cover the antigen diversity observed among population groups. This review examines the extent to which genomics is shaping blood group serology. Resources for genomics include the Human Reference Genome Sequence assembly; curated blood group tables listing variants; public databases providing information on genetic variants from world-wide studies; and massively parallel sequencing technologies. Blood group genomic studies span the spectrum, from bioinformatic data mining of huge data sets containing whole genome and whole exome information to laboratory investigations utilising targeted sequencing approaches. Blood group predictions based on genome sequencing and genomic studies are proving accurate, and have shown utility in both research and reference settings. Overall, studies confirm the potential for blood group genomics to reshape donor and patient transfusion management strategies to provide more compatible blood transfusions.

Transfusion Support of Minority Patients: Extended Antigen Donor Typing and Recruitment of Minority Blood Donors

One of the most important and persistent complications of blood transfusion is red blood cell (RBC) alloimmunization. When a patient is exposed to RBC antigens that differ from their own they can form alloantibodies to these foreign antigens. Blood group antigens are highly conserved and follow ancestral patterns of inheritance that may demonstrate population restriction. Minority populations who require chronic transfusion are at particularly high risk of alloimmunization when the blood donor population does not share the same ancestral background, resulting in exposure to non-self RBC antigens. It is incumbent on blood collectors to support patients with risk factors for alloimmunization as well as patients who have already formed alloantibodies. Increasing utilization of RBC genotyping may represent an opportunity to improve access to RBC units from donors that match the extended RBC phenotype of all possible patients.

Red blood cells, still vital after all these years: Commentary on Canadian Blood Services' International Symposium 2017

Canadian Blood Services (CBS), Canada's national blood transfusion service, has for many years sponsored an annual conference, for the education and awareness of interested participants, showcasing the latest evidence-based understanding of both basic science and clinical issues in transfusion medicine and science. The 15th iteration of this symposium took place September 9, 2017 and focused on some of the vital aspects of red blood cells (RBC), in line with the" 3Rs" concept, namely the provision of the Right red blood cell (RBC) product to the Right patient at the Right time. Presentations touched upon: the evolution of blood banking in North America; the monocyte monolayer assay as a predictor of post-transfusion hemolysis; hemoglobin-based oxygen carriers; RBC alloimmunization; serological approaches to complex RBC antibody problems; randomized clinical trials related to the age of stored RBC; RBC genotyping; pathophysiology, prevention and treatment of hemolytic disease of the fetus and newborn (HDFN); and testing and timing in perinatal serology. This commentary provides summaries of all speakers' presentations annotated with relevant references. Special thanks are due to all contributors for their praiseworthy approaches in sharing their experiences and knowledge on this interesting scientific/clinical and management theme.