Application of Blood Group Genotyping by Next-Generation Sequencing in Various Immunohaematology Cases

Simultaneous high throughput genotyping of 36 blood group systems using NGS based on probe capture technology

Human blood group antigen has important biological functions, and transfusion of incompatible blood can cause alloimmunization and may lead to serious hemolytic reactions. Currently, serological methods are most commonly used in blood group typing. However, this technique has certain limitations and cannot fully meet the increasing demand for the identification of blood group antigens. This study describes a next-generation sequencing (NGS) technology platform based on exon and flanking region capture probes to detect full coding exon and flanking intron regions of the 36 blood group systems, providing a new high-throughput method for the identification of blood group antigens. The 871 capture probes were designed for the exon and flanking intron sequences of 36 blood group system genes, and synchronization analysis for 36 blood groups was developed. The library for NGS was tested using the MiSeq Sequencing Reagent Kit (v2, 300 cycles) by Illumina NovaSeq, and the data were analyzed by the CLC Genomics Workbench 21.0 software. A total of 199 blood specimens have been sequenced for the 41 genes from 36 blood groups. Among them, heterozygote genotypes were found in the ABO, Rh, MNS, Lewis, Duffy, Kidd, Diego, Gerbich, Dombrock, Globoside, JR, LAN, and Landsteiner-Wiene blood group systems. Only the homozygous genotype was found in the remaining 22 blood group systems. The obtained data in the NGS method shows a good correlation (99.98 %) with those of the polymerase chain reaction-sequence-based typing. An NGS technology platform for 36 blood group systems genotyping was successfully established, which has the characteristics of high accuracy, high throughput, and wide coverage.

Next Generation Sequencing of Red Blood Cell Antigens in Transfusion Medicine: Systematic Review and Meta-Analysis

Molecular analysis of blood groups is important in transfusion medicine, allowing the prediction of red blood cell (RBC) antigens. Many blood banks use single nucleotide variant (SNV) based methods for blood group analysis. While this is a well-established approach, it is limited to the polymorphisms included in genotyping panels. Thus, variants that alter antigenic expression may be ignored, resulting in incorrect prediction of phenotypes. The popularization of next-generation sequencing (NGS) has led to its application in transfusion medicine, including for RBC antigens determination. The present review/meta-analysis aimed to evaluate the applicability of the NGS for the prediction of RBC antigens. A systematic review was conducted following a comprehensive literature search in accordance with the Preferred Reporting Items for Systematic Review and Meta-Analysis guidelines. Studies were selected based on predefined criteria and evaluated using Strengthening the Reporting of Observational studies in Epidemiology guidelines. The characteristics and results of the studies were extracted and meta-analysis was performed to verify the agreement between results from standard molecular methods and NGS. Kell (rs8176058), Duffy (rs2814778, rs12078), or Kidd (rs1085396) alleles were selected as a model for comparisons. Additionally, results are presented for other blood group systems. Of the 864 eligible studies identified, 10 met the inclusion criteria and were selected for meta-analysis. The pooled concordance proportion for NGS compared to other methods ranged from 0.982 to 0.994. The sequencing depth coverage was identified as crucial parameters for the reliability of the results. Some studies reported difficulty in analyzing more complex systems, such as Rh and MNS, requiring the adoption of specific strategies. NGS is a technology capable of predicting blood group phenotypes and has many strengths such as the possibility of simultaneously analyzing hundred individuals and gene regions, and the ability to provide comprehensive genetic analysis, which is useful in the description of new alleles and a better understanding of the genetic basis of blood groups. The implementation of NGS in the routine of blood banks depends on several factors such as cost reduction, the availability of widely validated panels, the establishment of clear quality parameters and access to bioinformatics analysis tools that are easy to access and operate.

Prevalence and molecular basis of null blood group phenotypes in the Korean population: Analysis using a public database

BACKGROUND

Null phenotypes are characterized by complete absence of all antigens within a blood group system and caused by null variants (e.g., nonsense, frameshift, initiation codon, and canonical splice site variants) in the genes encoding the antigens. Knowing the prevalence and molecular basis of null phenotypes is essential to establish a rare donor program, and the aim of this study was to reveal the prevalence and molecular basis of null phenotypes using the Korean Reference Genome Database (KRGDB) containing whole-genome sequences of 1722 Korean individuals.

STUDY DESIGN AND METHODS

Population allele frequencies of null alleles in 39 blood group systems except ABO, MNS, Rh, Lewis, and FORS were obtained from the KRGDB. The prevalence of null phenotypes was calculated using Hardy-Weinberg equation.

RESULTS

The prevalence of null phenotypes were estimated to be less than 0.001% in all blood group systems except JR and SID. The prevalence of the Jr(a-) and Sd(a-) phenotypes were estimated to be 0.0453% and 0.2323%, respectively. The most frequent null allele of the JR system was ABCG2*01N.01, accounting for approximately 85% of null alleles.

DISCUSSION

Our approach using a public database allowed us to investigate the prevalence and molecular basis of null phenotypes in the Korean population, which will serve as a guide for establishing a rare donor program in Korea. Considering the clinical significance, Jr(a-) is an important null phenotype that should be typed in the Korean population, and molecular assays targeting the most frequent allele ABCG2*01N.01 may be useful in detecting this phenotype.

[External Quality Control in Immunohematology of National Medical Center's Blood Bank. History and present]

For the proper functioning of the Immunohematology Area, an External Quality Control was established since 1973 through a program that evaluates the performance of the laboratories of the Blood Bank and transfusion services that carry out immunohematology tests. This program consists of sending panel cells to participating blood banks or services, which are phenotyped erythrocyte samples previously studied as problem cases but whose results are unknown by the participating laboratories. The processes in which the program is of most importance are determination of the ABO group, determination of Rh, performance of the direct and indirect Coombs test, and pre-transfusion compatibility tests. It was carried out an observational and retrospective study of the results obtained in the 2020 period from 104 units participating in the Immunohematology Quality Control Program of the National Medical Center's Blood Bank. A panel of cells was sent for external quality control of immunohematology every 45 days, resulting in 9 panels for each unit in the studied period. Compliance with the program was observed in the general result (79.6%), i.e., there was a decrease in the participation of the registered units. Of a maximum score of 100% to be obtained, it was observed a general result of 95.3% compliance of the participating units. The results obtained confirm the good general training of the immunohematology laboratories of the participating units. Yet, as in any external control program, it becomes clear that obtaining an erroneous result is a risk that can occur in any laboratory.