Determination of 24 minor red blood cell antigens for more than 2000 blood donors by high-throughput DNA analysis

The Lombardy Rare Donor Programme

BACKGROUND

In 2005, the government of Lombardy, an Italian region with an ethnically varied population of approximately 9.8 million inhabitants including 250,000 blood donors, founded the Lombardy Rare Donor Programme, a regional network of 15 blood transfusion departments coordinated by the Immunohaematology Reference Laboratory of the Ca' Granda Ospedale Maggiore Policlinico in Milan. During 2005 to 2012, Lombardy funded LORD-P with 14.1 million euros.

MATERIALS AND METHODS

During 2005-2012 the Lombardy Rare Donor Programme members developed a registry of blood donors and a bank of red blood cell units with either rare blood group phenotypes or IgA deficiency. To do this, the Immunohaematology Reference Laboratory performed extensive serological and molecular red blood cell typing in 59,738 group O or A, Rh CCDee, ccdee, ccDEE, ccDee, K- or k- donors aged 18-55 with a record of two or more blood donations, including both Caucasians and ethnic minorities. In parallel, the Immunohaematology Reference Laboratory implemented a 24/7 service of consultation, testing and distribution of rare units for anticipated or emergent transfusion needs in patients developing complex red blood cell alloimmunisation and lacking local compatible red blood cell or showing IgA deficiency.

RESULTS

Red blood cell typing identified 8,747, 538 and 33 donors rare for a combination of common antigens, negative for high-frequency antigens and with a rare Rh phenotype, respectively. In June 2012, the Lombardy Rare Donor Programme frozen inventory included 1,157 red blood cell units. From March 2010 to June 2012 one IgA-deficient donor was detected among 1,941 screened donors and IgA deficiency was confirmed in four previously identified donors. From 2005 to June 2012, the Immunohaematology Reference Laboratory provided 281 complex red blood cell alloimmunisation consultations and distributed 8,008 Lombardy Rare Donor Programme red blood cell units within and outside the region, which were transfused to 2,365 patients with no untoward effects.

DISCUSSION

Lombardy Rare Donor Programme, which recently joined the ISBT Working Party on Rare Donors, contributed to increase blood transfusion safety and efficacy inside and outside Lombardy.

Alternative blood products and clinical needs in transfusion medicine

The primary focus of national blood programs is the provision of a safe and adequate blood supply. This goal is dependent on regular voluntary donations and a regulatory infrastructure that establishes and enforces standards for blood safety. Progress in ex vivo expansion of blood cells from cell sources including peripheral blood, cord blood, induced pluripotent stem cells, and human embryonic stem cell lines will likely make alternative transfusion products available for clinical use in the near future. Initially, alloimmunized patients and individuals with rare blood types are most likely to benefit from alternative products. However, in developed nations voluntary blood donations are projected to be inadequate in the future as blood usage by individuals 60 years and older increases. In developing nations economic and political challenges may impede progress in attaining self-sufficiency. Under these circumstances, ex vivo generated red cells may be needed to supplement the general blood supply.

Routine use of DNA testing for red cell antigens in blood centres

During the last decade a number of blood establishments started using molecular methods for typing a subset of their blood donors for minor red cell antigens as a part of their routine work. It can be expected that this development will continue and that DNA testing will take a significant role in future. A sufficient number of antigen-typing in the donor-database allows for the efficient supply of red cell units for patients who carry irregular antibodies directed to red cell antigens. Therefore blood centres often operate antigen typing programs for a subset of their repeat donors. Large-scale donor typing programs are labour-intensive and costly. DNA testing is a feasible alternative to standard serological assays. The most important advantage is the easy access to a spectrum of hundreds of antigens independent of the availability of serological reagents. Besides, that there are both positive, but also less favourable aspects, which are related to the different particular methods and platforms available for molecular testing. Several of them enable medium- and high-throughput applications and some are more cost-efficient than serology.

DNA-based methods in the immunohematology reference laboratory

Although hemagglutination serves the immunohematology reference laboratory well, when used alone, it has limited capability to resolve complex problems. This overview discusses how molecular approaches can be used in the immunohematology reference laboratory. In order to apply molecular approaches to immunohematology, knowledge of genes, DNA-based methods, and the molecular bases of blood groups are required. When applied correctly, DNA-based methods can predict blood groups to resolve ABO/Rh discrepancies, identify variant alleles, and screen donors for antigen-negative units. DNA-based testing in immunohematology is a valuable tool used to resolve blood group incompatibilities and to support patients in their transfusion needs.

Population genetics of GYPB and association study between GYPB*S/s polymorphism and susceptibility to P. falciparum infection in the Brazilian Amazon

BACKGROUND

Merozoites of Plasmodium falciparum invade through several pathways using different RBC receptors. Field isolates appear to use a greater variability of these receptors than laboratory isolates. Brazilian field isolates were shown to mostly utilize glycophorin A-independent invasion pathways via glycophorin B (GPB) and/or other receptors. The Brazilian population exhibits extensive polymorphism in blood group antigens, however, no studies have been done to relate the prevalence of the antigens that function as receptors for P. falciparum and the ability of the parasite to invade. Our study aimed to establish whether variation in the GYPB*S/s alleles influences susceptibility to infection with P. falciparum in the admixed population of Brazil.

METHODS

Two groups of Brazilian Amazonians from Porto Velho were studied: P. falciparum infected individuals (cases); and uninfected individuals who were born and/or have lived in the same endemic region for over ten years, were exposed to infection but have not had malaria over the study period (controls). The GPB Ss phenotype and GYPB*S/s alleles were determined by standard methods. Sixty two Ancestry Informative Markers were genotyped on each individual to estimate admixture and control its potential effect on the association between frequency of GYPB*S and malaria infection.

RESULTS

GYPB*S is associated with host susceptibility to infection with P. falciparum; GYPB*S/GYPB*S and GYPB*S/GYPB*s were significantly more prevalent in the in the P. falciparum infected individuals than in the controls (69.87% vs. 49.75%; P<0.02). Moreover, population genetics tests applied on the GYPB exon sequencing data suggest that natural selection shaped the observed pattern of nucleotide diversity.

CONCLUSION

Epidemiological and evolutionary approaches suggest an important role for the GPB receptor in RBC invasion by P. falciparum in Brazilian Amazons. Moreover, an increased susceptibility to infection by this parasite is associated with the GPB S+ variant in this population.

Benefits of blood group genotyping in multi-transfused patients from the south of Brazil

We evaluated the usefulness of blood group genotyping as a supplement to hemagglutination to determine the red blood cell (RBC) antigen profile of polytransfused patients with hematological diseases and renal failure. Seventy-nine patients were selected. They all received more than three units of blood and eight (10%) had already clinical significant alloantibodies occurring alone or in combination against Rh, K, Fya, and Di antigens. DNA was prepared from blood samples and RHCE*E/e, KEL*01/KEL*02, FY*01/FY*02 and JK*01/JK*02 alleles were determined by using PCR-RFLP. RHD*/RHD*Ψ and RHCE*C/c were tested using multiplex PCR. Discrepancies for Rh, Kell, Duffy, and Kidd systems were found between the phenotype and genotype-derived phenotype in 16 of the 38 chronically transfused patients. The genotypes of these patients were confirmed by DNA array analysis (HEA Beadchip(™); Bioarray Solutions, Warren, NJ). Genotyping was very important for the determination of the true blood groups of the polytransfused patients, helped in the identification of suspected alloantibodies and in the selection of antigen-negative RBCs for transfusion.

A Microsphere-Based Suspension Array for Blood Group Molecular Typing: An Update

SUMMARY: BACKGROUND: In a previous publication we described a method for Jk(a)/Jk(b), Fy(a)/Fy(b), S/s, K/k, Kp(a)/Kp(b), Js(a)/Js(b), Co(a)/Co(b), and Lu(a)/Lu(b) genotyping based on a microsphere suspension array. Here, an improved version of the assay is presented. METHODS: TWO MULTIPLEX POLYMERASE CHAIN REACTIONS (PCR) WERE DEVELOPED: one for amplification of samples routinely tested and the other for those systems that are tested less frequently. Each biotinylated PCR product is hybridized in a single multiplex assay. A total of 2,020 samples were analyzed, and the genotypes were compared to the blood group phenotypes. RESULTS: There have been no discrepancies with the serology results other than null and/or weak phenotypes. CONCLUSION: In its present form, the method presented here has the capacity to genotype hundreds of a samples in few hours with a high concordance rate with serology.

Future of molecular testing for red blood cell antigens

When one looks at the field of molecular pathology or transplantation, it is evident that molecular biology has made a positive impact on medicine. However, the progress in transfusion medicine has been slower and more cautious than in other areas of the clinical laboratory. To understand where the field may go in the next 10 years requires that the reader understand what technology is available now. Therefore, this article discusses the current state of the art for red-cell genotyping and newer, ever-evolving molecular technologies. Because it is impossible to present all of the molecular techniques and their variations in this article, the author selects a group of methodologies to review and speculates where the field of molecular immunohematology may be in 2020.

Blood still kills: six strategies to further reduce allogeneic blood transfusion-related mortality

After reviewing the relative frequency of the causes of allogeneic blood transfusion-related mortality in the United States today, we present 6 possible strategies for further reducing such transfusion-related mortality. These are (1) avoidance of unnecessary transfusions through the use of evidence-based transfusion guidelines, to reduce potentially fatal (infectious as well as noninfectious) transfusion complications; (2) reduction in the risk of transfusion-related acute lung injury in recipients of platelet transfusions through the use of single-donor platelets collected from male donors, or female donors without a history of pregnancy or who have been shown not to have white blood cell (WBC) antibodies; (3) prevention of hemolytic transfusion reactions through the augmentation of patient identification procedures by the addition of information technologies, as well as through the prevention of additional red blood cell alloantibody formation in patients who are likely to need multiple transfusions in the future; (4) avoidance of pooled blood products (such as pooled whole blood-derived platelets) to reduce the risk of transmission of emerging transfusion-transmitted infections (TTIs) and the residual risk from known TTIs (especially transfusion-associated sepsis [TAS]); (5) WBC reduction of cellular blood components administered in cardiac surgery to prevent the poorly understood increased mortality seen in cardiac surgery patients in association with the receipt of non-WBC-reduced (compared with WBC-reduced) transfusion; and (6) pathogen reduction of platelet and plasma components to prevent the transfusion transmission of most emerging, potentially fatal TTIs and the residual risk of known TTIs (especially TAS).

The relationship between blood groups and disease

The relative contribution of founder effects and natural selection to the observed distribution of human blood groups has been debated since blood group frequencies were shown to differ between populations almost a century ago. Advances in our understanding of the migration patterns of early humans from Africa to populate the rest of the world obtained through the use of Y chromosome and mtDNA markers do much to inform this debate. There are clear examples of protection against infectious diseases from inheritance of polymorphisms in genes encoding and regulating the expression of ABH and Lewis antigens in bodily secretions particularly in respect of Helicobacter pylori, norovirus, and cholera infections. However, available evidence suggests surviving malaria is the most significant selective force affecting the expression of blood groups. Red cells lacking or having altered forms of blood group-active molecules are commonly found in regions of the world in which malaria is endemic, notably the Fy(a-b-) phenotype and the S-s- phenotype in Africa and the Ge- and SAO phenotypes in South East Asia. Founder effects provide a more convincing explanation for the distribution of the D- phenotype and the occurrence of hemolytic disease of the fetus and newborn in Europe and Central Asia.

How to find, recruit and maintain rare blood donors

PURPOSE OF REVIEW

Since the early 1960s, it was recognized that patients with very complex serology may be limited in the availability of rare blood for transfusion. Over the years, there have been publications about the quest to meet those needs. Although the world's literature on how to find, recruit and maintain rare blood donors is not overwhelming, there are quite a few pearls. This review will seek out those pearls published in 2007-2009 and provides some insight from a perspective of having a responsibility for a nation of patients requiring rare blood for over 15 years.

RECENT FINDINGS

Most pertinent publications have focused on a particular country and the data gathered by a particular regional area or the national rare donor program. It is clear that the definition of 'rare' varies from country to country. A blood type rare in one country may not be considered rare in another. A few of the publications that will be reviewed are specific to donor recruitment or specific details regarding a particular blood type. Recently, with the advent of semi-automated equipment to assist in DNA analysis, there has been a volley of articles on the use of this equipment.Without effective rare donor programs, there is a risk that transfusion needs may not be met. Hemovigilance concentrates on adverse events related to blood transfusions, and the event that happens when rare blood is not available may be that the patient dies without the transfusion they need.

SUMMARY

The need for rare blood has been recognized for nearly 50 years, and there are some very effective programs across the world, but not all the areas of the world are equally supplied. The International Society of Blood Transfusion Working Party for Rare Donors is a vital link in the worldwide goal of providing rare blood to the patients who need it.

High-throughput red blood cell antigen genotyping using a nanofluidic real-time polymerase chain reaction platform

BACKGROUND

Serologic testing of donors to obtain antigen-negative blood for transfusion is limited by availability and quality of reagents. Where sequence variant information is available, molecular typing platforms can be used to determine the presence of a variant allele and offer a high-throughput format correlated to the blood group antigen. We have investigated a flexible high-throughput platform to screen blood donors for antigen genotypes in the African American population.

STUDY DESIGN AND METHODS

Genomic DNA from 427 African American donors was analyzed for single-nucleotide polymorphisms responsible for red blood cell (RBC) antigens E/e, Fy(a)/Fy(b), Fy gene promoter, Jk(a)/Jk(b), Lu(a)/Lu(b), K/k, Js(a)/Js(b), Do(a)/Do(b), Jo(a), and Hy using primer/probe sets (Taqman, Applied Biosystems) on a high-throughput genotyping platform (OpenArray, BioTrove). Where available, the phenotype obtained by serologic testing was compared to genotype data.

RESULTS

Serologic antigen types were available for 2037 of the 4270 genotypes generated. There were five discordant results. Three resolved with repeat serologic typing, one resolved after repeat genotyping, and one discordance was clarified by confirmation of the BioTrove genotype by Sanger sequencing. Triplicate determinations were made for each sample genotype and the results were identical more than 99% of the time.

CONCLUSIONS

The nanofluidic genotyping platform described here provides an accurate method for predicting blood group phenotypes. The user-specified array layout provides flexibility of target selection and number of replicate determinations and is suitable for screening antigen types.

Blood groups: the past 50 years

Since the first issue of TRANSFUSION in 1961, there has been a tremendous expansion in not only the number of blood group antigens identified but also in our knowledge of their biochemical basis, function, and more recently, associated DNA changes. As certain techniques became available, our ability to discover and elucidate blood group antigens and appreciate their contribution to biology became possible. In particular, Western blotting, monoclonal antibodies, cloning, and polymerase chain reaction-based assays have led to an explosion of our knowledge base. The study of blood groups has had a significant effect on human genetics where they serve as useful markers in genetic linkage analyses. Indeed blood groups have provided several "firsts" in certain aspects of genetics. Blood group-null phenotypes, as natural human knockouts, have provided valuable insights into the importance of red blood cell membrane components. This review summarizes key aspects of the discovery of blood groups; the inconsistent terminology that has arisen; and the contribution of blood groups to genetics, safe transfusion, transplantation, evolution, and biology.

The molecular genetics of blood group polymorphism

Over 300 blood group specificities on red cells have been identified, many of which are polymorphic. The molecular mechanisms responsible for these polymorphisms are diverse, though many simply represent single nucleotide polymorphisms (SNPs). Other mechanisms include the following: gene deletion; single nucleotide deletion and sequence duplication, which introduce reading-frame shifts; nonsense mutation; intergenic recombination between closely linked genes, giving rise to hybrid genes and hybrid proteins; and a SNP in the promoter region of a blood group gene. Examples of these various genetic mechanisms are taken from the ABO, Rh, Kell, and Duffy blood group systems. Null phenotypes, in which no antigens of a blood group system are expressed, are not generally polymorphic, but provide good examples of the effect of inactivating mutations on blood group expression. As natural human 'knock-outs', null phenotypes provide useful clues to the functions of blood group antigens. Knowledge of the molecular backgrounds of blood group polymorphisms provides a means to predict blood group phenotypes from genomic DNA. This has two main applications in transfusion medicine: determination of foetal blood groups to assess whether the foetus is at risk from haemolytic disease and ascertainment of blood group phenotypes in multiply transfused, transfusion-dependent patients, where serological tests are precluded by the presence of donor red cells. Other applications are being developed for the future.

Red cell genotyping and the future of pretransfusion testing

Over the past 20 years the molecular bases of almost all the major blood group antigens have been determined. This research has enabled development of DNA-based methods for determining blood group genotype. The most notable application of these DNA-based methods has been for determining fetal blood group in pregnancies when the fetus is at risk for hemolytic disease of the fetus and newborn. The replacement of all conventional serologic methods for pretransfusion testing by molecular methods is not straightforward. For the majority of transfusion recipients matching beyond ABO and D type is unnecessary, and the minority of untransfused patients at risk of alloimmunization who would benefit from more extensively blood group–matched blood cannot be identified reliably. Even if a method to identify persons most likely to make alloantibodies were available, this would not of itself guarantee the provision of extensively phenotype-matched blood for these patients because this is determined by the size and racial composition of blood donations available for transfusion. However, routine use of DNA-based extended phenotyping to provide optimally matched donations for patients with preexisting antibodies or patients with a known predisposition to alloimmunization, such as those with sickle cell disease, is widely used.

Blood group genotyping: from patient to high-throughput donor screening

Blood group antigens, present on the cell membrane of red blood cells and platelets, can be defined either serologically or predicted based on the genotypes of genes encoding for blood group antigens. At present, the molecular basis of many antigens of the 30 blood group systems and 17 human platelet antigens is known. In many laboratories, blood group genotyping assays are routinely used for diagnostics in cases where patient red cells cannot be used for serological typing due to the presence of auto-antibodies or after recent transfusions. In addition, DNA genotyping is used to support (un)-expected serological findings. Fetal genotyping is routinely performed when there is a risk of alloimmune-mediated red cell or platelet destruction. In case of patient blood group antigen typing, it is important that a genotyping result is quickly available to support the selection of donor blood, and high-throughput of the genotyping method is not a prerequisite. In addition, genotyping of blood donors will be extremely useful to obtain donor blood with rare phenotypes, for example lacking a high-frequency antigen, and to obtain a fully typed donor database to be used for a better matching between recipient and donor to prevent adverse transfusion reactions. Serological typing of large cohorts of donors is a labour-intensive and expensive exercise and hampered by the lack of sufficient amounts of approved typing reagents for all blood group systems of interest. Currently, high-throughput genotyping based on DNA micro-arrays is a very feasible method to obtain a large pool of well-typed blood donors. Several systems for high-throughput blood group genotyping are developed and will be discussed in this review.

Microarray Beads for Identifying Blood Group Single Nucleotide Polymorphisms

We have developed a high-throughput system for single nucleotide polymorphism (SNP) genotyping of alleles of diverse blood group systems exploiting Luminex technology. The method uses specific oligonucleotide probes coupled to a specific array of fluorescent microspheres and is designed for typing Jk(a)/Jk(b), Fy(a)/Fy(b), S/s, K/k, Kp(a)/Kp(b), Js(a)/Js(b), Co(a)/Co(b) and Lu(a)/Lu(b) alleles. Briefly, two multiplex PCR reactions (PCR I and PCR II) according to the laboratory specific needs are set up. PCR I amplifies the alleles tested routinely, namely Jk(a)/Jk(b), Fy(a)/Fy(b), S/s, and K/k. PCR II amplifies those alleles that are typed less frequently. Biotinylated PCR products are hybridized in a single multiplex assay with the corresponding probe mixture. After incubation with R-phycoerythrin-conjugated streptavidin, the emitted fluorescence is analyzed with Luminex 100. So far, we have typed more than 2,000 subjects, 493 of whom with multiplex assay, and there have been no discrepancies with the serology results other than null and/or weak phenotypes. The cost of consumables and reagents for typing a single biallelic pair per sample is less than EUR 3.-, not including DNA extraction costs. The capability to perform multiplexed reactions makes the method markedly suitable for mass screening of red blood cell alleles. This genotyping approach represents an important tool in transfusion medicine.

[Genotyping of blood group systems at the CNRGS. I: FY, JK, MNS systems]

AIM OF THE STUDY

Determination of blood group antigens from data obtained by using molecular methods (genotyping) has become an indispensable tool in the specialized immunohematology laboratories. The French National Reference Centre for Blood group typing (CNRGS) routinely performs genotyping of the FY, JK and MNS system (common genotyping), providing a phenotype deduced from genotyping data for FY1, FY2, JK1, JK2, MNS3 and MNS4 antigens.

PATIENTS AND METHODS

We performed a study to evaluate the common genotyping prescriptions referred to the CNRGS over the last three years.

RESULTS

Between February 2006 and February 2009, the CNRGS performed 2392 genotyping, including 981 common genotyping. Analysis of 172 common genotyping performed in 2008 showed that 63.8% of the prescriptions expressed a genotyping demand. Of the latter, 42.7% were genotyping prescriptions only, whereas 57.2% were prescriptions of genotyping associated with alloantibody identification. All prescriptions refer to blood group genotyping indications issued from guidelines, with no incorrect prescription, that are patients transfused within four months before blood sampling in 63.6% of cases or a positive direct antiglobulin test in 24.5% of cases. Lastly, 36% of the blood samples referred to the CNRGS had no genotyping prescription. Yet, common genotyping was performed by the CNRGS to get complete immunohematology data for antibody identification.

CONCLUSION

Usefulness of blood group genotyping in specialized immunohematology laboratories is obvious. However, the strategy for implementation of molecular methods remains to be defined. Use of high-throughput DNA analysis should change our way of working.

DNA array analysis for red blood cell antigens facilitates the transfusion support with antigen-matched blood in patients with sickle cell disease

BACKGROUND

Blood samples from patients with sickle cell disease (SCD) present to transfusion service with numerous antibodies, making the searching for compatible red blood cells (RBC) a challenge. To overcome this problem we developed an effective strategy to meet needs of supplying RBC-compatible units to SCD patients using DNA arrays.

METHODS

We selected DNA samples from 144 SCD patients with multiple (receiving > 5 units) transfusions previously phenotyped for ABO, Rh(D, C, c, E, e), K1, Fy(a) and Jk(a). We also selected DNA samples from 948 Brazilian blood donors whose ABO/RhD phenotype matched that of the patients. All samples were analysed by DNA array analysis (HEA Beadchip(TM), Bioarray Solutions) to determine polymorphisms associated with antigen expression for 11 blood group systems (Rh, Kell, Kidd, Duffy, MNS, Dombrock, Lutheran, Landsteiner-Wiener, Diego, Colton, Scianna); and one mutation associated with haemoglobinopathies.

RESULTS

Based on genotype results we were able to predict phenotype-compatible donors needed in order to provide compatible units to this group of patients. Based on their ABO/Rh phenotype we were able to find in this pool of donors compatible units for 134 SCD patients.

CONCLUSION

Blood group genotyping by DNA array contributes to the management of transfusions in SCD patients by facilitating the transfusion support with antigen-matched blood. It has the potential to improve the life of thousands of SCD-transfused patients by reducing mortality due to transfusion reactions and immunization.

Set-up and routine use of a database of 10,555 genotyped blood donors to facilitate the screening of compatible blood components for alloimmunized patients

BACKGROUND AND OBJECTIVES

Large-scale genotyping of blood donors for red blood cell and platelet antigens has been predicted to replace phenotyping assays in the screening of compatible blood components for alloimmunized patients. Although several genotyping platforms have been described, novel procedures and processes are needed to perform genotyping efficiently and to maximize its benefits for blood banks.

MATERIALS AND METHODS

Here we describe the processes and procedures developed to introduce large-scale genotyping in our routine operations.

RESULTS

Preliminary cost-benefit analysis indicated that genotyping must target frequent blood donors (> 3 donations/year) to be efficiently used. A custom-designed computer application was developed to manage the whole project. It selects frequent donors among recent donations, prints coded labels to identify blood samples sent to the external genotyping laboratory, and stores genotyping results. It can search for donors compatible for any combination of the 22 genotyped antigens as well as consult the current inventory for the presence of the corresponding blood components. The phenotype of recovered components is confirmed by standard serology techniques prior to shipment to hospitals.

CONCLUSION

Since October 2007, 10 555 blood donors have been genotyped. The database is used on a regular basis to find compatible blood components with a genotype-phenotype concordance of 99.6%.

Molecular biology of the Rh system: clinical considerations for transfusion in sickle cell disease

The last decade has witnessed an abundance of information detailing the genetic diversity of the RH locus which has exceeded all estimates predicted by serology. Well over 120 RHD and over 60 different RHCE alleles have been documented, and new alleles are still being discovered. For clinical transfusion medicine, RH genetic testing can now be used to determine RHD zygosity, resolve D antigen status, and detect altered RHD and RHCE genes in individuals at risk for producing antibodies to high-incidence Rh antigens, particularly patients with sickle cell disease (SCD).

Transfusion in the age of molecular diagnostics

DNA-based tests are increasingly being used to predict a blood group phenotype to improve transfusion medicine. This is possible because genes encoding 29 of the 30 blood group systems have been cloned and sequenced, and the molecular bases associated with most antigens have been determined. RBCs carrying a particular antigen, if introduced into the circulation of an individual who lacks that antigen (through transfusion or pregnancy), can elicit an immune response. It is the antibody from such an immune response that causes problems in clinical practice and the reason why antigen-negative blood is required for safe transfusion. The classical method of testing for blood group antigens and antibodies is hemagglutination; however, it has certain limitations, some of which can be overcome by testing DNA. Such testing allows conservation of antibodies for confirmation by hemagglutination of predicted antigen-negativity. High-throughput platforms provide a means to test relatively large numbers of donors, thereby opening the door to change the way antigen-negative blood is provided to patients and to prevent immunization. This review summarizes how molecular approaches, in conjunction with conventional hemagglutination, can be applied in transfusion medicine.

Applications and Experience with PCR-Based Assays to Predict Blood Group Antigens

DNA-based tests are increasingly being used to predict a blood group phenotype. This is possible because genes encoding 29 of the 30 blood group systems have been cloned and sequenced, and the molecular bases associated with most antigens have been determined. RBCs carrying a particular antigen, if introduced into the circulation of an individual who lacks that antigen, can elicit an immune response. It is the antibody from such an immune response that causes problems in clinical practice and the reason why antigen-negative blood is required for safe transfusion. The classical method of testing for blood group antigens and antibodies is hemagglutination; however, it has certain limitations, some of which can be overcome by testing DNA. Such testing allows conservation of antibodies for confirmation by hemagglutination of predicted antigen-negativity. High-throughput platforms provide a means to test relatively large numbers of donors, thereby opening the door to change the way antigen-negative blood is provided to patients. This chapter discusses how molecular approaches can be applied in transfusion medicine, and summarizes experiences of using laboratory developed tests and DNA arrays at the New York Blood Center.

Large-scale blood group genotyping: clinical implications

The molecular background of blood group antigen expression of the major clinically significant blood group antigens has been largely accomplished. Despite this large body of work, blood group phenotype prediction by genotyping has a marginal supporting role in the routine blood bank. It has however had a major impact in the prenatal determination of fetal blood group status in the management of haemolytic disease of the fetus and newborn. In the past few years several high throughput systems have been in development that have the potential capacity to perform genotyping on a mass scale. Such systems have been designed for use on donor- and patient-derived DNA and provide much more comprehensive information regarding an individuals blood group than is possible by using serological methods alone. DNA-based typing methodology is easier to standardize than serology and has the potential to replace it as a front line diagnostic in blood banks. This review overviews the current situation in this area and attempts to predict how blood group genotyping will evolve in the future.

New technologies to replace current blood typing reagents

PURPOSE OF REVIEW

This review summarizes recent developments in blood grouping and compatibility testing in transfusion medicine.

RECENT FINDINGS

Identification of the molecular characteristics of the major human blood groups has provided an opportunity to develop methods for blood group phenotyping using DNA-based technology. Various studies have demonstrated the feasibility of such an approach and have demonstrated the potential to change current procedures for identifying compatible blood, both in routine settings and in highly immunized patients, for whom compatible blood is difficult to obtain. In the obstetric setting, isolation of cell-free DNA from maternal plasma for fetal blood grouping provides a minimally invasive method for determining the risk for haemolytic disease in the newborn. Recombinant technology for synthesizing blood group proteins, although in its infancy, has the potential to change longstanding antibody identification procedures.

SUMMARY

The molecular revolution occurring throughout medicine is broadly manifest in all areas of transfusion medicine and should contribute to transfusion safety.