Red cell genotyping and the future of pretransfusion testing

Mapping anticipated advantages and disadvantages of implementation of extensive donor genotyping: A focus group approach

BACKGROUND AND OBJECTIVES

Current genotyping techniques allow typing of all relevant red cell, human leukocyte and platelet antigens in a single analysis. Even genetic markers related to donor health can be added. Implementation of this technology will affect various stakeholders within the transfusion chain. This study aims to systematically map the anticipated advantages and disadvantages of a national rollout of blood group genotyping of donors, which will affect the availability of rare donors and the implementation of an extensively typed blood transfusion policy.

MATERIALS AND METHODS

Two focus-group sessions were held with a wide representation of stakeholders, including representatives of donor and patient organisations. A dedicated software tool was used to collect the reflections of participants on genotyping for blood group antigens and extensive matching. Additionally, stakeholders and experts discussed various prepared propositions. All information collected was categorised.

RESULTS

From 162 statements collected, 59 statements (36%) were labelled as 'hopes' and 77 (48%) as 'fears'. Twenty-six (16%) statements remained unlabelled. The statements were divided in 18 categories under seven main themes: patient health, genotyping, privacy issues and ethical aspects, donor management, inventory management and logistics, hospital and transfusion laboratory and general aspects. The discussion on the propositions was analysed and summarised.

CONCLUSION

Stakeholders believe that a genotyped donor pool can result in a reduction of alloimmunization and higher availability of typed blood products. There are concerns regarding logistics, costs, consent for extended typing, data sharing, privacy issues and donor management. These concerns need to be carefully addressed before further implementation.

Logical Analysis of Multiple Single-Nucleotide-Polymorphisms with Programmable DNA Molecular Computation for Clinical Diagnostics

Analyzing complex single-nucleotide-polymorphism (SNP) combinations in the genome is important for research and clinical applications, given that different SNP combinations can generate different phenotypic consequences. Recent works have shown that DNA-based molecular computing is powerful for simultaneously sensing and analyzing complex molecular information. Here, we designed a switching circuit-based DNA computational scheme that can integrate the sensing of multiple SNPs and simultaneously perform logical analysis of the detected SNP information to directly report clinical outcomes. As a demonstration, we successfully achieved automatic and accurate identification of 21 different blood group genotypes from 83 clinical blood samples with 100 % accuracy compared to sequencing data in a more rapid manner (3 hours). Our method enables a new mode of automatic and logical sensing and analyzing subtle molecular information for clinical diagnosis, as well as guiding personalized medication.

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

BACKGROUND

Next-generation sequencing (NGS) technology has been recently introduced into blood group genotyping; however, there are few studies using NGS-based blood group genotyping in real-world clinical settings. In this study, we applied NGS-based blood group genotyping into various immunohaematology cases encountered in routine clinical practice.

METHODS

This study included 4 immunohaematology cases: ABO subgroup, ABO chimerism, antibody to a high-frequency antigen (HFA), and anti-CD47 interference. We designed a hybridization capture-based NGS panel targeting 39 blood group-related genes and applied it to the 4 cases.

RESULTS

NGS analysis revealed a novel intronic variant (NM_020469.3:c.29-10T>G) in a patient with an Ael phenotype and detected a small fraction of ABO*A1.02 (approximately 3-6%) coexisting with the major genotype ABO*B.01/O.01.02 in dizygotic twins. In addition, NGS analysis found a homozygous stop-gain variant (NM_004827.3:c.376C>T, p.Gln126*; ABCG2*01N.01) in a patient with an antibody to an HFA; consequently, this patient's phenotype was predicted as Jr(a-). Lastly, blood group phenotypes predicted by NGS were concordant with those determined by serology in 2 patients treated with anti-CD47 drugs.

CONCLUSION

NGS-based blood group genotyping can be used for identifying ABO subgroup alleles, low levels of blood group chimerism, and antibodies to HFAs. Furthermore, it can be applied to extended blood group antigen matching for patients treated with anti-CD47 drugs.

Molecular genotyping of Indian blood group antigens amongst regular voluntary blood donors of Surat city, Gujarat, India

BACKGROUND

There is paucity of data related to the prevalence of the rare blood group antigens amongst South Gujarat blood donor population due to unavailability and high cost of antisera. Therefore it is difficult to screen donors for such rare antigens by gold standard haemagglutination assay. The single nucleotide polymorphism (SNPs) of In^a and In^b antigens is the base of the PCR based detection methods that help to detect these alleles in regular voluntary blood donors.

MATERIALS & METHODS

Blood samples of 200 unrelated regular voluntary blood donors wee collected. DNA was extracted using phenol-chloroform method and genotyped for Indian (In^a/IN*01, In^b/IN*02) blood group alleles by Sequence Specific PCR. In^a antigen positivity was confirmed by serology test.

RESULTS

Four donors were found heterozygous for In^a antigen i.e. In (a + b+) by SS-PCR and their In^a positivity were confirmed by in-house polyclonal Anti-In^a reagent. SS-PCR was standardized using known heterozygous sample of a blood donor. The frequency of In^a antigen (2.0 %) was higher than Caucasians, lower than Iranians and Arabs while comparable to those reported among Indians of Mumbai city.

CONCLUSION

In absence or unavailability of antisera particularly for low frequency alleles like In^a, such PCR based method would be extremely helpful to prepare rare donor registry by screening blood donors' at large scale. Red cells of In^a positive donors can be used as in-house reagent red cells for screening and identification of corresponding antibody.

Molecular red cell genotyping of rare blood donors in South Africa to enhance rare donor-patient blood matching

BACKGROUND

Molecular red cell genotyping is devoid of serology limitations such as the scarcity of rare antisera and the possibility of inconclusive results due to biological interferences. Blood incompatibility can result in immune transfusion reactions such as haemolytic transfusion reactions or haemolytic disease of the foetus and newborn.

OBJECTIVE

The study aimed to use molecular red cell genotyping to identify rare blood group donors among South African blood donors.

METHODS

Red cell genotyping data were extracted retrospectively from the BIDS XT genotyping software in the Immunohaematology Reference Laboratory from January 2015 to August 2016. The ID CORE XT genotyping assay was used to identify the single nucleotide polymorphisms of 10 blood groups system alleles in 150 donors. Associations between the resultant genotypes and predicted phenotypes, ABO group, RhD type, race group and gender were studied.

RESULTS

Significant red cell genetic variability was noted among the numerous South African donor genotypes identified in this study. Genotyping further confirmed the presence of at least one of the 16 rare genotypes in 50 donors. Group O Black donors were associated with two rare blood types, while several other rare blood types were found only in White donors, supporting an association between ABO/Rh subtype, race group and rare blood types.

CONCLUSION

Targeted screening of donors for antigen-negative rare blood units for patients should be done to reduce the risk of haemolytic transfusion reactions and haemolytic disease of the foetus and newborn.

Preanalytic depletion of medicinal anti-CD38 antibody from patient plasma for immunohematology testing

Monoclonal antibodies such as daratumumab that target antigens that are also expressed on red blood cells impede blood group typing. The preferred approach to potential transfusion is to do prior extensive antigen typing of patients' red cells; however, this is not always possible. Ehrend et al describe a technique for absorbing the antibodies from serum to allow accurate red cell typing for transfusion.

HLA-DRB1 molecules and the presentation of anchor peptides from RhD, RhCE, and KEL proteins

BACKGROUND

Antigens from the Rh and Kell systems are recognized as the most immunogenic in clinical practice. This study evaluated the possible molecular mechanisms involved in the interaction of antigenic peptides with the DRB1 molecules, which help to explain the high frequency of anti-K and association of D + C antibodies in transfusion and incompatible pregnancy.

STUDY DESIGN AND METHODS

We included 201 patients with antibodies against antigens from the Rh and Kell systems and compare them with 174,015 controls. HLA-DRB1 genotyping and in silico analysis were performed. The NetMHCIIpan software was used to identify RhD-, RhCE-, and KEL-derived anchor peptides that bind to DRB1 molecules.

RESULTS

HLA-DRB1*15 is associated with an increased risk of D, C, E, and K alloimmunization, while the HLA-DRB1*01 and *12 alleles are overrepresented in patients with anti-C and anti-D, respectively. In silico analysis showed that three polymorphic points (60I, 68S, and 103S) common to C and D antigens can be presented by several DRB1 molecules, including DRB1*15:01. The DRB1*09:01 molecule, although not showing statistical significance, was able to interact strongly with almost all five anchor peptides from the sequence containing the polymorphic determinants of E antigen, except 217-WMFWPSVNS-225.

CONCLUSION

The DRB1*15 molecule has specific physicochemical characteristics in residues 11P and 13R in the P4 pocket that can favor the response to various antigenic peptides. Anti-K alloimmunization is unrestricted for interaction with specific DRB1 molecules, which suggests that almost all individuals in our population have DRB1 molecules capable of binding to KEL-derived anchor peptides and produce anti-K when stimulated.

ABO maternal-child discordance: Evidence of variable allelic expression and considerations for investigation

BACKGROUND

We report a case of apparent mother-child ABO group noninheritance. A Caucasian mother initially typed as group O and her infant group AB. Investigation ruled out preanalytical causes such as mislabeled samples and in vitro fertilization.

MATERIALS AND METHODS

Red blood cells were characterized by routine serologic testing. Genomic data were analyzed by targeted polymerase chain reaction-restriction fragment length polymorphism and Sanger sequencing. Transferase structures were modeled using PyMOL molecular visualization software.

RESULTS

Serologic testing initially demonstrated the mother was group O, father group AB, and infant group AB. Further testing of the maternal sample with anti-A,B demonstrated weak A expression. Molecular testing revealed the maternal sample had an ABO*O.01.01 allele in trans to an A allele, ABO*AW.29 (c.311T>A, p.Ile104Asn), determined by gene sequencing. The sample from the infant carried the same ABO*AW.29 allele in trans to a B allele, ABO*B.01.

CONCLUSION

ABO genotyping revealed an A transferase encoded by ABO*AW.29, with apparent variable activity. Although A antigen expression is well known to be weak in newborns, it was robust on the red blood cells (RBCs) of the AB infant and undetectable with anti-A on the mother. Variable expression of weak subgroups may reflect competition or enhancement by a codominant allele, as well as glycan chain maturation on red cells. Previous examples in group AB mothers with A_weak infants suggested that the decreased expression is primarily due to glycan immaturity. To our knowledge, this is the first reported case of the ABO*AW.29 allele presenting with weak A expression in a group A_weak mother and robust A expression in a group AB infant, suggesting the in trans allele is an important factor in determining transferase activity and may override age-related effects.

The Potential Significance of ABO Genotyping for Donor Selection in Kidney Transplantation

Background

The ABO blood group system is clinically important in kidney transplantation, but ABO genotyping fails to attract sufficient attention in some countries and regions. We identified one case of early graft dysfunction due to an ABO genotype mismatch. Here, we performed ABO genotyping in blood samples, analyzed grouping discrepancies, and investigated the weak A subgroup frequency in kidney transplantation candidates.

Methods

Blood samples from 302 uremic patients with grouping discrepancies and 356 uremic patients with type A blood were analyzed using standard serologic serotyping techniques. The ABO genotypes and alleles were analyzed by polymerase chain reaction sequence-specific primer (PCR-SSP) and sequence-based typing (PCR-SBT).

Results

All 302 uremic patients with grouping discrepancies carried weak ABO subgroup alleles and 77.48% carried irregular ABO antibodies. The discrepancy rate between serotyping and genotyping was 42.38%, and the mismatching rate of donor selection according to serotype reached 88.74%. And 2.53% of 356 uremic patients with type A blood were determined to be in the weak A subgroup, which was a higher percentage than that observed in the healthy Chinese population (0.53%) by serological screening, but much lower than that observed in Caucasians (20%).

Conclusion

We revealed the high risk of blood type misjudgment and genetically ABO-mismatched transplantation if serological test was performed only in blood-group typing. Improved precision of ABO genotyping is crucial for successful kidney transplantation and reasonable organ allocation.

Non-invasive prenatal testing for management of haemolytic disease of the fetus and newborn induced by maternal alloimmunisation

Anti-D immunoglobulin prophylaxis reduces the risk of RhD negative women becoming alloimmunised to the RhD antigen and is a major preventative strategy in reducing the burden of haemolytic disease of the fetus and newborn (HDFN). HDFN also arises from other maternal red cell antibodies, with the most clinically significant, after anti-D, being anti-K, anti-c and anti-E. Among the 39 human blood group systems advanced genomic technologies are still revealing novel or rare antigens involved in maternal alloimmunisation. Where clinically significant maternal antibodies are detected in pregnancy, non-invasive prenatal testing (NIPT) of cell-free fetal DNA provides a safe way to assess the fetal blood group antigen status. This provides information as to the risk for HDFN and thus guides management strategies. In many countries, NIPT fetal RHD genotyping as a diagnostic test using real-time PCR has already been integrated into routine clinical care for the management of women with allo-anti-D to assess the risk for HDFN. In addition, screening programs have been established to provide antenatal assessment of the fetal RHD genotype in non-alloimmunised RhD negative pregnant women to target anti-D prophylaxis to those predicted to be carrying an RhD positive baby. Both diagnostic and screening assays exhibit high accuracy (over 99 %). NIPT fetal genotyping for atypical (other than RhD) blood group antigens presents more challenges as most arise from a single nucleotide variant. Recent studies show potential for genomic and digital technologies to provide a personalised medicine approach with NIPT to assess fetal blood group status for women with other (non-D) red cell antibodies to manage the risk for HDFN.

Targeted exome sequencing designed for blood group, platelet, and neutrophil antigen investigations: Proof-of-principle study for a customized single-test system

BACKGROUND

Immunohematology reference laboratories provide red blood cell (RBC), platelet (PLT), and neutrophil typing to resolve complex cases, using serology and commercial DNA tests that define clinically important antigens. Broad-range exome sequencing panels that include blood group targets provide accurate blood group antigen predictions beyond those defined by serology and commercial typing systems and identify rare and novel variants. The aim of this study was to design and assess a panel for targeted exome sequencing of RBC, PLT, and neutrophil antigen-associated genes to provide a comprehensive profile in a single test, excluding unrelated gene targets.

STUDY DESIGN AND METHODS

An overlapping probe panel was designed for the coding regions of 64 genes and loci involved in gene expression. Sequencing was performed on 34 RBC and 17 PLT/neutrophil reference samples. Variant call outputs were analyzed using software to predict star allele diplotypes. Results were compared with serology and previous sequence genotyping data.

RESULTS

Average coverage exceeded 250×, with more than 94% of targets at Q30 quality or greater. Increased coverage revealed a variant in the Scianna system that was previously undetected. The software correctly predicted allele diplotypes for 99.5% of RBC blood groups tested and 100% of PLT and HNA antigens excepting HNA-2. Optimal throughput was 12 to 14 samples per run.

CONCLUSION

This single-test system demonstrates high coverage and quality, allowing for the detection of previously overlooked variants and increased sample throughput. This system has the potential to integrate genomic testing across laboratories within hematologic reference settings.

Genetic variability of blood groups in southern Brazil

We evaluated genetic variability among the blood groups Kell (c.578C > T and c.1790T > C), Kidd (c.838A > G), Duffy (c.125A > G, c.265C > T and c.1-67T > C), Diego (c.2561C > T), MNS (c.143T > C) and Rh (c.676G > C) in Rio Grande do Sul in southern Brazil. Genetic profiling from 382 volunteer blood donors was performed through allelic discrimination assays using a hydrolysis probe (TaqMan®) with a real-time PCR system. The sample was divided into two groups: Euro-Brazilian and Afro-Brazilian. A comparison with studies from other regions of Brazil and the 1000 Genomes Database showed significant differences for almost all polymorphisms evaluated in our population. Population differentiation between the Euro- and Afro-Brazilian groups was low (FST value 0.055). However, when each locus was evaluated individually, KEL*06 and FY*02N.01 allele frequencies were significantly higher in the Afro-Brazilian group than in the Euro-Brazilian group. Ethnic classification that uses phenotypic criteria to find blood units with rare antigens may be important when there is a need to detect blood units with an absence of Duffy antigens. There is also a greater probability of finding donors in the Afro-Brazilian group. Taken together, the data indicate strong European and African contributions to the gene pool, with intense admixture.

Hemolysis From Intravenous Immunoglobulin in Obese Patients With Kawasaki Disease

Objective: We assessed the risk of IVIG-associated hemolytic anemia in patients with acute Kawasaki disease (KD) and evaluated the risk of weight-based dosing in our obese patients. Methods: IVIG-associated hemolytic anemia was assessed in acute KD patients treated with IVIG at Rady Children's Hospital-San Diego. Patients in whom hemolytic anemia was suspected had a decrease in z-score of their hemoglobin (zHgb) at least two standard deviations below the cohort's mean change in zHgb from baseline to 2 weeks post-IVIG treatment. These patients were further evaluated for spherocytosis, blood type, need for transfusion, red cell distribution width, reticulocytosis, and direct Coombs test. Body mass index was calculated. Results: Of the 30 IVIG-resistant KD patients who received a second dose of IVIG, 2 (6.7%) developed hemolytic anemia after a total of 4 g/kg of IVIG dosed on actual body weight, or a mean of 4.6 g/kg of IVIG based on lean body mass. Compared to 496 non-obese KD patients who received a single dose of IVIG with no cases of hemolytic anemia, two (5.6%) of 36 obese KD patients developed hemolytic anemia after a single dose of IVIG (2 g/kg) dosed on actual body weight, or a mean of 2.7 g/kg IVIG based on lean body mass. Conclusions: In addition to following patients carefully for hemolytic anemia after a second dose of IVIG, physicians should consider IVIG dosing based on lean body mass for obese patients.

Evaluation of molecular typing and serological methods in solving discrepant results of weak and partial D (Rh) in South Egypt

INTRODUCTION

Rh discrepancies produced by partial and weak D phenotypes are a problem during routine testing. Some blood units with weak and partial D expression may be missed by serology. Overcoming the limitations of serology can be achieved by molecular typing. Our objective was to evaluate currently used serologic methods with the molecular analysis in solving discrepant results of weak and partial D (Rh) in South Egypt.

PATIENTS AND METHODS

Fifty blood donor and patient samples with undetermined D phenotype were subjected to serology to define their phenotype using identification (ID)-Card "ID-partial RhD typing set" using six monoclonal anti-D panels, followed by molecular typing using polymerase chain reaction sequence-specific primer kit.

RESULTS

Molecular typing confirmed most of the serology results; two samples previously resolved as partial D Type 3 and DFR by serological methods were clarified by molecular techniques - one sample as weak Type 4 and the other sample as weak Type 3. Among the weak D alleles found in our study, Type 4 was the most common, with a frequency of 20%, followed by Type 3 (14%), Type 1 (8%), Type 2 (6%), and finally, Type 5 with a frequency of 3%. The most common types of partial D were partial D Type D5 (14%) and Type D3 (10%).

CONCLUSION

Our study identified D variants (weak D and partial D categories) of the antigen D and determined the frequency and composition of partial D and weak D alleles in our population. Molecular typing also confirmed most of the results obtained from serological methods.

Blood group antigen and phenotype prevalence in the Korean population compared to other ethnic populations and its association with RBC alloantibody frequency

OBJECTIVES

This study aimed to analyse the allele frequency of blood group antigens in the Korean population and other ethnic populations and the association of blood group antigens with red blood cell (RBC) alloantibodies.

BACKGROUND

Blood group antigen genotyping can support patients undergoing frequent transfusions who have alloantibodies and antibodies against high-prevalence blood group antigens.

METHODS

Twenty-nine single nucleotide variations and 37 blood group antigens were tested. Samples requested for routine blood typing were collected from Jan to Apr 2016. Genotyping was performed on 145 Korean samples and was confirmed by bidirectional sequencing and serologic tests. The allele frequency data were compared with previous genotyping datasets (three datasets from Korea and one each from China, Europe, Asia, and the USA). Alloantibody frequencies and blood group antigens from the electronic medical record of 1772 cases were examined.

RESULTS

E antigen was higher in the Korean population compared to that of Asian and European populations. K, Kp^a , Fy^b and Do^a allele frequencies were lower compared to other ethnic populations. RBC alloantibodies with frequencies (%) greater than 1% from the 1772 cases were as follows: anti-E, 36·7%, anti-C, 17·7%; anti-c 7·39%; anti-M, 5·9%; anti-e, 5·2%; anti-Jk^a , 2·9%; and anti-Fy^a , 1·1%. Blood group antigens and alloantibody frequencies revealed inverse trends that did not reach statistical significance.

CONCLUSION

The allele frequency of blood group antigens assessed by high-throughput methods provided reliable and valuable information that could be used for maintaining donor pools and providing compatible blood for genotyped patients.

Genotyping of Dombrock and Lutheran blood group systems in blood donors from the southwestern region of the state of Paraná, Southern Brazil

Background

Lutheran and Dombrock are two blood group systems with low immunogenic antigens; they can cause mild-to-moderate transfusion reactions. For both, immunophenotyping is not performed in the pretransfusion routine in Brazil. In addition, the distribution of their antigenic frequencies is an important marker of ethnicity. Thus, the goal of this study was to carry out the genotyping of the LU*01, LU*02, DO*01 and DO*02 alleles of the Lutheran and Dombrock blood group systems in blood donors from the southwestern region of the state of Paraná, Southern Brazil.

Method

Genotyping was performed for 251 blood donors by specific allele-polymerase chain reaction. The genotype and allele frequencies were obtained through direct counting and compared with other Brazilian populations using the chi-square test with Yates correction.

Results

The distribution of genotype frequencies for LU were 0.4% for LU*01/LU*01, 6.8% for LU*01/LU*02 and 92.8% for LU*02/LU*02 and for DO, they were 19.9% for DO*01/DO*01, 44.6% for DO*01/DO*02 and 35.5% for DO*02/DO*02. The allele and genotype frequencies of LU and DO were similar to those expected for Caucasians, but the DO*01/DO*01 genotype frequency was different to other Brazilian populations. The rare LU*01/LU*01 genotype was found in a loyal blood donor.

Conclusion

The genotyping techniques allowed the evaluation of the LU*01, LU*02, DO*01 and DO*02 alleles in blood donors registered in the Hemotherapy Center of the southwestern region of Paraná, Southern Brazil, and contributed to a genotyped blood donor database.

Comprehensive blood group antigen profile predictions for Western Desert Indigenous Australians from whole exome sequence data

BACKGROUND

The distribution of RBC antigens, which define blood group types, differs among populations. In contrast to many world populations, blood group profiles for Indigenous Australians have not been well studied. As it is now possible to predict comprehensive blood group antigen profiles from genomic data sets, we aimed to apply this for Indigenous Australians and to provide a comparison to other major world populations.

STUDY DESIGN AND METHODS

Whole exome sequence data for 72 Western Desert Indigenous Australians was provided by the Telethon Kids Institute. Variants (against hg19) were annotated using computer software (ANNOVAR, Qiagen Bioinformatics) and filtered to include only variants in genes for 36 blood group systems, and the transcription factors KLF1 and GATA1. The RHCE*C allele and RHD zygosity were identified by copy number variant analysis of sequence alignments. The impact of missense variants was investigated in silico using a meta-predictor of disease-causing variants (Meta-SNP).

RESULTS

For 21 blood group systems the predicted blood group antigen frequencies were comparable to those for other major world populations. For 13 systems, interesting points of contrast were identified. Furthermore, we identified 12 novel variants, one novel D allele, and four rare variants with potential clinical significance.

CONCLUSION

This is the first systematic assessment of genomic data to elucidate blood group antigen profiles for Indigenous Australians who are linguistically and culturally diverse. Our study paves the way to understanding the geographic distribution of blood group variants in different Indigenous groups and the associated RBC phenotypes. This in turn is expected to guide transfusion practice for Indigenous individuals.

Methods for blood group antigens detection: cost-effectiveness analysis of phenotyping and genotyping

Background

Alloimmunization is a major problem in transfusion practice due to the clinical complications of the patients and the difficulty of choosing a unit of compatible blood product. Serological methods are widely used in blood banks, but they not always determine the phenotype. Thus, genotyping is an important complement to the serology tool as it allows one to predict the phenotype from deoxyribonucleic acid (DNA) with high accuracy.

Objective

To compare the centrifugation gel, microarray, Restriction Fragment Length Polymorphismone PCR (PCR-RFLP) and Sequence-Specific Primer PCR (PCR-SSP) techniques, in terms of cost, reaction time and reliability of the results.

Methods

The RHCE, Kidd, Kell and Duffy blood group systems were chosen to determine the approximate cost of each technique, considering the reagents used in both methods and considering only one sample. The time required for the development of each reaction was obtained at the Maringa Regional Blood Center and Immunogenetics Laboratory at the State University of Maringa. Data from Microarray reactions were obtained at the Campinas Blood Center. The results of phenotyping and genotyping of the 16 samples were compiled in a spreadsheet and compared.

Results

The PCR-SSP was more economical compared to other methods, and the serological method was faster than the molecular methods. However, all methods proved to be effective and safe in the detection of erythrocyte antigens.

Conclusion

Analyzing the advantages and limitations of the molecular and serological methods tested in this study, we note that both are important and complementary. However, the choice of a methodology depends on the reality and needs of each health service.

Red Blood Cell Agglutination for Blood Typing Within Passive Microfluidic Biochips

Pre-transfusion bedside compatibility test is mandatory to check that the donor and the recipient present compatible groups before any transfusion is performed. Although blood typing devices are present on the market, they still suffer from various drawbacks, like results that are based on naked-eye observation or difficulties in blood handling and process automation. In this study, we addressed the development of a red blood cells (RBC) agglutination assay for point-of-care blood typing. An injection molded microfluidic chip that is designed to enhance capillary flow contained anti-A or anti-B dried reagents inside its microchannel. The only blood handling step in the assay protocol consisted in the deposit of a blood drop at the tip of the biochip, and imaging was then achieved. The embedded reagents were able to trigger RBC agglutination in situ, allowing for us to monitor in real time the whole process. An image processing algorithm was developed on diluted bloods to compute real-time agglutination indicator and was further validated on undiluted blood. Through this proof of concept, we achieved efficient, automated, real time, and quantitative measurement of agglutination inside a passive biochip for blood typing which could be further generalized to blood biomarker detection and quantification.

Matching phenotypes to whole genomes: Lessons learned from four iterations of the personal genome project community challenges

The advent of next-generation sequencing has dramatically decreased the cost for whole-genome sequencing and increased the viability for its application in research and clinical care. The Personal Genome Project (PGP) provides unrestricted access to genomes of individuals and their associated phenotypes. This resource enabled the Critical Assessment of Genome Interpretation (CAGI) to create a community challenge to assess the bioinformatics community's ability to predict traits from whole genomes. In the CAGI PGP challenge, researchers were asked to predict whether an individual had a particular trait or profile based on their whole genome. Several approaches were used to assess submissions, including ROC AUC (area under receiver operating characteristic curve), probability rankings, the number of correct predictions, and statistical significance simulations. Overall, we found that prediction of individual traits is difficult, relying on a strong knowledge of trait frequency within the general population, whereas matching genomes to trait profiles relies heavily upon a small number of common traits including ancestry, blood type, and eye color. When a rare genetic disorder is present, profiles can be matched when one or more pathogenic variants are identified. Prediction accuracy has improved substantially over the last 6 years due to improved methodology and a better understanding of features.

Blood Group Distribution in Switzerland - a Historical Comparison

BACKGROUND

Ethnicities differ in prevalence of blood groups and antigens. Substantial donor-recipient mismatch within mixed-ethnic societies may render certain recipients at higher risk for alloimmunization. Data regarding antigen distribution within Switzerland by ethnicity is limited. We examined immigration patterns against the distribution of ABO blood groups using large cross-sectional Swiss samples spanning 70 years.

METHODS

Historical ABO blood group distribution data (1940-1945) from Swiss army personnel (n = 275,664) were sourced from the literature. Recent blood group phenotypes of 122,925 individuals who presented themselves at army recruitment centers (2004-2015) were obtained, alongside a validation sample of 175,202 patients from a university hospital. Two-sample tests with z-statistics assessing blood groups between samples were used.

RESULTS

The respective proportions of A (47.2% and 45.2%), B (8.4% and 9.8%), and AB (3.0 and 4.1) in the historical and recent army samples were significantly different (p < 0.001), while group O was not. Conclusion: ABO blood groups in Switzerland have remained stable despite substantial immigration with a changing foreign-national profile. Further research is needed to improve the understanding of antigen differences in newly introduced ethnic groups. Blood product requirements and public health initiatives aimed at recruiting blood donors would benefit from this information.

Importance of extended blood group genotyping in multiply transfused patients

Blood group antigen systems are not limited to the ABO blood groups. There is increasing interest in the detection of extended blood group systems on the red cell surface. The conventional method used to determine extended blood group antigens or red cell phenotype is by serological testing, which is based on the detection of visible haemagglutination or the presence of haemolysis. However, this technique has many limitations due to recent exposure to donor red cell, certain drugs or medications or other diseases that may alter the red cell membrane. We aimed to determine the red cell blood group genotype by SNP real time PCR and to compare the results with the conventional serological methods in multiply transfused patients. Sixty-three patients participated in this study whose peripheral blood was collected and blood group phenotype was determined by serological tube method while the genotype was performed using TaqMan^® Single Nucleotide Polymorphism (SNP) RT-PCR assays for RHEe, RHCc, Kidd and Duffy blood group systems. Discrepancies were found between the phenotype and genotype results for all blood groups tested. Accurate red blood cell antigen profiling is important for patients requiring multiple transfusions. The SNP RT-PCR platform is a reliable alternative to the conventional method.

RH genotypes among Malaysian blood donors

Background: RH genotyping studies have been conducted mainly in people of Caucasian and African descent. There is limited information regarding the molecular basis for RH genotypes in Malaysia.

Objectives: To investigate the prevalence and characteristics of RHCE genotypes among different ethnic groups in Malaysia.

Methods: A total of 1014 whole blood samples were obtained from donors from 4 different ethnic groups (360 Malays, 434 Chinese, 164 Indians, and 56 others). All samples were phenotyped for C, c, D, E, and e using standard serologic methods and genotyped using polymerase chain reaction (PCR)-based analysis.

Results: In the blood samples that we analyzed, the distribution of RH genotype antigens was significantly different among the various ethnic groups. Our findings showed that CCDee is the most common in Malaysian blood donors; 18.4% (187/1014) compared with other genotypes. The ccDEE genotype is more prevalent in the Chinese: 65.6% (82/125), and the ccee genotype is more prevalent in Indians: 47.1% (65/138). There were discrepancies between phenotypes and genotypes. There were 17 (1.7%) discrepancies in RH C/c genotyping results and of these 47% (8/17) occurred in Malays. Discrepancies in RH E/e results occurred in 3 samples (0.3%).

Conclusions: Our study provides a database for the distribution of RH genotypes of donors from the major ethnic groups in Malaysia. Methods used in this study are useful for comparing the phenotypes and genotypes. Further investigation should be conducted to study the causes of these discrepancies using other molecular based techniques.

Erythrogene: a database for in-depth analysis of the extensive variation in 36 blood group systems in the 1000 Genomes Project

Blood group genotyping has recently developed into a clinical tool to improve compatibility of blood transfusions and management of pregnancies. Next-generation sequencing (NGS) is rapidly moving toward routine practice for patient and donor typing and has the potential to remedy some of the limitations of currently used platforms. However, a large-scale investigation into the blood group genotypes obtained by NGS in a multiethnic cohort is lacking. The 1000 Genomes Project provides information on genome variation among 2504 individuals representing 26 populations worldwide. We extracted their NGS data for all 36 blood group systems to a custom-designed database. In total, 210 412 alleles from 43 blood group-related genes were imported and curated. Matching algorithms were developed to compare them to blood group variants identified to date. Of the 1241 non-synonymous variants identified in the coding regions, 241 are known blood group polymorphisms. Interestingly, 357 of the remaining 1000 variants are predicted to occur on extracellular portions of 31 different blood group-carrying proteins and some may represent undiscovered antigens. Of the alleles analyzed, 1504 were not previously described. The ABO/GBGT1/FUT2/FUT3 and GYPB/GYPC genes showed the highest degree of variation per kilobase coding sequence, and ACKR1 variants had the most skewed distribution across 5 continental superpopulations in the dataset. Results were exported to an online search engine, www.erythrogene.com, which presents data according to the allele nomenclature developed for clinical reporting by the International Society of Blood Transfusion. The established database deepens our knowledge on blood group polymorphism globally and provides a long-sought platform for future research.

Emerging strategies of blood group genotyping for patients with hemoglobinopathies

Red cell alloimmunization is a serious problem in chronically transfused patients. A number of high-throughput DNA assays have been developed to extend or replace traditional serologic antigen typing. DNA-based typing methods may be easily automated and multiplexed, and provide reliable information on a patient. Molecular genotyping promises to become cheaper, being not dependent on serologic immunoglobulin reagents. Patients with hemoglobinopathies could benefit from receiving extended genomic typing. This could limit post transfusional complications depending on subtle antigenic differences between donors and patients. Patient/donor compatibility extended beyond the phenotype Rh/Kell may allows improved survival of transfused units of red blood cells (RBC) and lead to reduced need for blood transfusion and leading to less iron overload and reduced risk of alloimmunization. Here we discuss the advantages and limitations of current techniques, that detect only predefined genetic variants. In contrast, target enrichment next-generation sequencing (NGS) has been used to detect both known and de novo genetic polymorphisms, including single-nucleotide polymorphisms, indels (insertions/deletions), and structural variations. NGS approaches can be used to develop an extended blood group genotyping assay system.

Advances in Blood Typing

The clinical importance of blood group antigens relates to their ability to evoke immune antibodies that are capable of causing hemolysis. The most important antigens for safe transfusion are ABO and D (Rh), and typing for these antigens is routinely performed for patients awaiting transfusion, prenatal patients, and blood donors. Typing for other blood group antigens, typically of the Kell, Duffy, Kidd, and MNS blood groups, is sometimes necessary, for patients who have, or are likely to develop antibodies to these antigens. The most commonly used typing method is serological typing, based on hemagglutination reactions against specific antisera. This method is generally reliable and practical for routine use, but it has certain drawbacks. In recent years, molecular typing has emerged as an alternative or supplemental typing method. It is based on detecting the polymorphisms and mutations that control the expression of blood group antigens, and using this information to predict the probable antigen type. Molecular typing methods are useful when traditional serological typing methods cannot be used, as when a patient has been transfused and the sample is contaminated with red blood cells from the transfused blood component. Moreover, molecular typing methods can precisely identify clinically significant variant antigens that cannot be distinguished by serological typing; this capability has been exploited for the resolution of typing discrepancies and shows promise for the improved transfusion management of patients with sickle cell anemia. Despite its advantages, molecular typing has certain limitations, and it should be used in conjunction with serological methods.

Evaluation of a high throughput method for the detection of mutations associated with thrombosis and hereditary hemochromatosis in Brazilian blood donors

Background

The aim of this study was to evaluate the OpenArray platform for genetic testing of blood donors and to assess the genotype frequencies of nucleotide-polymorphisms (SNPs) associated with venous thrombosis (G1691A and G20210A), hyperhomocysteinemia (C677T, A1298C), and hereditary hemochromatosis (C282Y, H63D and S65C) in blood donors from Sao Paulo, Brazil.

Methods

We examined 400 blood donor samples collected from October to November 2011. The SNPs were detected using OpenArray technology. The blood samples were also examined using a real-time PCR–FRET system to compare the results and determine the accuracy of the OpenArray method.

Results

We observed 100% agreement in all assays tested, except HFE C282Y, which showed 99.75% agreement. The HFE C282Y assay was further confirmed through direct sequencing, and the results showed that OpenArray analysis was accurate. The calculated frequencies of each SNP were FV G1691A 98.8% (G/G), 1.2% (G/A); FII G2021A 99.5% (G/G), 0.5% (G/A); MTHFR C677T 45.5% (C/C), 44.8% (C/T), 9.8% (T/T); MTHFR A1298C 60.3% (A/A), 33.6% (A/C), 6.1% (C/C); HFE C282Y 96%(G/G), 4%(G/A), HFE H63D 78.1%(C/C), 20.3% (C/G), 1.6% (G/G); and HFE S65C 98.1% (A/A), 1.9% (A/T).

Conclusion

Taken together, these results describe the frequencies of SNPs associated with diseases and are important to enhance our current knowledge of the genetic profiles of Brazilian blood donors, although a larger study is needed for a more accurate determination of the frequency of the alleles. Furthermore, the OpenArray platform showed a high concordance rate with standard FRET RT-PCR.

BOOGIE: Predicting Blood Groups from High Throughput Sequencing Data

Over the last decade, we have witnessed an incredible growth in the amount of available genotype data due to high throughput sequencing (HTS) techniques. This information may be used to predict phenotypes of medical relevance, and pave the way towards personalized medicine. Blood phenotypes (e.g. ABO and Rh) are a purely genetic trait that has been extensively studied for decades, with currently over thirty known blood groups. Given the public availability of blood group data, it is of interest to predict these phenotypes from HTS data which may translate into more accurate blood typing in clinical practice. Here we propose BOOGIE, a fast predictor for the inference of blood groups from single nucleotide variant (SNV) databases. We focus on the prediction of thirty blood groups ranging from the well known ABO and Rh, to the less studied Junior or Diego. BOOGIE correctly predicted the blood group with 94% accuracy for the Personal Genome Project whole genome profiles where good quality SNV annotation was available. Additionally, our tool produces a high quality haplotype phase, which is of interest in the context of ethnicity-specific polymorphisms or traits. The versatility and simplicity of the analysis make it easily interpretable and allow easy extension of the protocol towards other phenotypes. BOOGIE can be downloaded from URL http://protein.bio.unipd.it/download/.

A simple genotyping procedure without DNA extraction to identify rare blood donors

BACKGROUND

Transfusion-induced alloimmunization has severe clinical consequences including haemolytic transfusion reactions, impaired transfused RBCs longevity and greater difficulty in finding compatible blood. Molecular analysis of genomic DNA now permits prediction of blood group phenotypes based on identification of single nucleotide polymorphisms. Implementation of molecular technologies in donor centres would be helpful in finding RBC units for special patient populations, but DNA extraction remains an obstacle to donor genotyping.

MATERIALS AND METHODS

We propose a simple method compatible with high throughput that allows blood group genotyping using a multiplex commercial kit without the need for DNA extraction. The principle relies on pre-PCR treatment of whole blood using heating/cooling procedure in association with a recombinant hotstart polymerase.

RESULTS

In a prospective analysis, we yielded 5628 alleles identification and designated 63 donors with rare blood, that is either negative for a high-frequency antigen or with a rare combination of common antigens.

CONCLUSION

The procedure was optimized for simplicity of use in genotyping platform and would allow not only to supply antigen-matched products to recipients but also to find rare phenotypes. This methodology could also be useful for establishing a donor repository for human platelet antigens (HPA)-matched platelets since the same issues are involved for patients with neonatal alloimmune thrombocytopenia or post-transfusion purpura.

Molecular basis of Rh blood group system in the Malaysian population

BACKGROUND

Rh molecular studies have been previously mainly conducted in Caucasians and African population. There is a limited data on the molecular basis for Rh genotypes among Asians.

AIMS

This study aims to characterize the Rh genes and frequency of the various RH genotypes among blood donors in National Blood Centre (NBC), Kuala Lumpur.

MATERIALS AND METHODS

A total of 1014 blood samples were obtained from blood donors from four different ethnic groups (360 Malays, 434 Chinese, 164 Indians and 56 others). Serological and molecular analysis of all 1014 blood samples were performed. An automated deoxyribonucleic acid sequencing analysis was performed.

RESULTS

Rh phenotypes and RH genotypes showed heterogeneity and significant association with ethnicities. Discrepancies in allele D, C/c and E/e between phenotypes and genotypes results were observed. Discrepancy results in allele D showed significant association with the ethnic groups of the blood donors in NBC. There were multiple novel mutations (23) and published mutations (5) found in this study. Significant associations between discrepancy results and mutations were found in allele D and C/c.

CONCLUSION

Performing RH molecular analysis in Malaysian population provided the basic database for the distribution of Rh genotypes of donors from major ethnic groups in Malaysia.

Erythrocyte genotyping for transfusion-dependent patients at the Azienda Universitaria Policlinico of Naples

BACKGROUND AND OBJECTIVES

Although minor erythrocyte antigens are not considered clinically significant in sporadic transfusions, they may be relevant for multi-transfusion patients. When serological assay is not conceivable, molecular genotyping allows predicting the red blood cell phenotype, extending the typing until minor blood groups. The aim of this study was to evaluate the utility of blood group genotyping and compare the molecular typing of erythrocyte antigens with the established serological methods.

MATERIALS AND METHODS

We selected 225 blood donors and 50 transfusion-dependent patients at the Division of Immunohematology of the Second University of Naples. Blood samples were analyzed with NEO Immucor automated system and genotyped for 38 red blood cell antigens and phenotypic variants with the kit HEA BeadChip™. The comparative study was conducted for RhCE and Kell antigens whose typing is available with both methods.

RESULTS

We observed a good correlation between serological and molecular methods for donors that were concordant for 99.5% (224/225) and discordant for 0.5% (1/225). Patients resulted concordant only for 46.0% (23/50) and discordant for 54.0% (27/50); discrepancies were 46.0% (23/50) and 8.0% (4/50) for RhCE and Kell systems respectively. Through molecular genotyping we also identified polymorphisms in RhCE, Kell, Duffy, Colton, Lutheran and Scianna loci in donors and patients.

CONCLUSIONS

Blood group genotyping is particularly useful for poly-transfused patients. Molecular analysis confirms and extends serological test data and then allows us to obtain a better match. This molecular assay can be used in the future to prevent alloimmunization in transfusion-dependent patients.

Duffy and kidd genotyping facilitates pretransfusion testing in patients undergoing long-term transfusion therapy

Objective: Conventional serologic typing of red blood cell systems other than ABO and RhD can be inaccurate and difficult to interpret in patients who have recently undergone blood transfusion. While molecular-based assays are not used routinely, the usefulness of genotyping was investigated in order to determine patients who may benefit from this procedure.

Materials and Methods: Blood samples were taken from 101 patients with haemato-oncological, chronic renal, or gastroenterological diseases and from 50 donor controls; the samples were tested for Fya and Fyb by applying serologic and genetic methods. All patients had received 3 or more units of RBCs during the last 3 months. An average of 6.1 RBC units were transfused per patient. The average length of time from transfusion until blood sampling was 24.4 days. The haemagglutination test was applied for serological analysis, and the restriction length polymorphism assay was used for genotyping.

Results: In total, 33 (32.7%) patients showed positive reactions with anti-Fya or anti-Fyb while being negative genetically. False-positive Fya results were found in 23 samples, and false-positive Fyb in 10 specimens. During the last 3 months, significantly more RBC units were transfused to patients with discrepant results than to those with accurate phenotyping/genotyping results: median of 5 (mean ± SE: 6.85±0.69) versus median of 4 (mean: 5.71±0.51), respectively (p=0.025). The median length of time after the last transfusion was 25 days (mean: 28.72±2.23 days) in the group with accurate phenotyping/genotyping results versus a median of 14 days (mean: 15.52±1.95 days) in the group with discrepant results (p=0.001). Phenotypes and genotypes coincided in all donor samples.

Conclusion: Genotyping assays for the Duffy system should be considered if the patient underwent blood transfusion less than 3 or 4 weeks before the sample collection. If the time frame from RBC transfusion exceeds 6 weeks, Duffy phenotyping can provide accurate results.

BGMUT Database of Allelic Variants of Genes Encoding Human Blood Group Antigens

The Blood group antigen Gene MUTation (BGMUT) database documents variations in genes of human blood group systems. In March 2014, the database, accessible at www.ncbi.nlm.nih.gov/gv/mhc/xslcgi.cgi?cmd=bgmut, listed 1,545 alleles of 44 genes of 34 blood group systems. Besides allelic information, the BGMUT resource also presents comprehensive and current information on blood group systems. This review describes the database and notes its utility for the transfusion medicine and human genetics communities.

Blood product transfusions and reactions

Blood product transfusions are an essential component of the practice of emergency medicine. From acute traumatic hemorrhage to chronic blood loss necessitating transfusion for symptomatic anemia, familiarity with individual blood products and their indications for transfusion is an essential tool for every emergency physician (EP). Although the focus of this article is primarily on the transfusion of red blood cells, many of the concepts are applicable to the transfusion of all blood products. EPs must be fully familiar with both the individual blood components and the potential reactions and complications of these transfusions.

Molecular typing for the Indian blood group associated 252G>C single nucleotide polymorphism in a selected cohort of Australian blood donors

BACKGROUND

The Indian blood group antigens, In(a) and In(b), are clinically significant in transfusion medicine. However, antisera to type these antigens are difficult to obtain. The In(b) antigen is a high frequency antigen present in all populations, while the frequency of the antithetical In(a) ranges from 0.1% in Caucasians up to 11% in Middle Eastern groups. This antigen polymorphism is encoded by the single nucleotide polymorphism (SNP) 252G>C in CD44. The aim of this study was to establish and compare two genotyping methods to measure the frequency of the IN*A and IN*B alleles in a blood donor cohort.

MATERIALS AND METHODS

Donor blood samples (n=151) were genotyped by a novel real-time polymerase chain reaction (PCR) high-resolution meltcurve (HRM) analysis and a custom matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) assay. Samples with the rare IN*A allele were further investigated by nucleotide sequencing, red cell agglutination, and flow cytometry techniques.

RESULTS

In this study group, 149 IN*B homozygous and 2 IN*A/B heterozygous samples were detected with 100% concordance between HRM and MALDI-TOF MS methods. For PCR HRM, amplicon melting alone did not differentiate IN*A and IN*B alleles (class 3 SNP), however, the introduction of an unlabelled probe (UP) increased the resolution of the assay. Sequencing confirmed that the two non-homozygous samples were IN*A/B heterozygous and phenotyping by red cell agglutination, and flow cytometry confirmed both In(a) and In(b) antigens were present as predicted.

DISCUSSION

Genotyping permits conservation of rare antisera to predict blood group antigen phenotype. In PCR UP-HRM the IN*A and IN*B alleles were discriminated on the basis of their melting properties. The In(a) frequency in this selected donor population was 1.3%. Application of genotyping methods such as these assists in identifying donors with rare blood group phenotypes of potential clinical significance.

Transfusion complications in thalassemia patients: a report from the Centers for Disease Control and Prevention (CME)

BACKGROUND

Transfusions are the primary therapy for thalassemia but have significant cumulative risks. In 2004, the Centers for Disease Control and Prevention (CDC) established a national blood safety monitoring program for thalassemia. This report summarizes the population and their previous nonimmune and immune transfusion complications.

STUDY DESIGN AND METHODS

The CDC Thalassemia Blood Safety Network is a consortium of centers longitudinally following patients. Enrollment occurred from 2004 through 2012. Demographics, transfusion history, infectious exposures, and transfusion and nontransfusion complications were summarized. Logistic regression analyses of factors associated with allo- and autoimmunization were employed.

RESULTS

The race/ethnicity of these 407 thalassemia patients was predominantly Asian or Caucasian. The mean ± SD age was 22.3 ± 13.2 years and patients had received a mean ± SD total number of 149 ± 103.4 units of red blood cells (RBCs). Multiorgan dysfunction was common despite chelation. Twenty-four percent of transfused patients had previous exposure to possible transfusion-associated pathogens including one case of babesia. As 27% were immigrants, the infection source cannot be unequivocally linked to transfusion. Transfusion reactions occurred in 48%, including allergic, febrile, and hemolytic; 19% were alloimmunized. Common antigens were E, Kell, and C. Years of transfusion was the strongest predictor of alloimmunization. Autoantibodies occurred in 6.5% and were associated with alloimmunization (p < 0.0001). Local institutional policies, not patient characteristics, were major determinants of blood preparation and transfusion practices.

CONCLUSION

Hemosiderosis, transfusion reactions, and infections continue to be major problems in thalassemia. New pathogens were noted. National guidelines for RBC phenotyping and preparation are needed to decrease transfusion-related morbidity.

ABO blood type and stroke risk: the REasons for Geographic And Racial Differences in Stroke Study

BACKGROUND

ABO blood type is an inherited trait associated with coagulation factor levels and vascular outcomes.

OBJECTIVES

To assess the association of blood type with stroke and whether blood type contributes to racial disparities in stroke in the United States.

PATIENTS AND METHODS

The REasons for Geographic And Racial Differences in Stroke (REGARDS) Study recruited 30 239 participants between 2003 and 2007. Using a case-cohort design, blood type was genotyped in 646 participants with stroke and a 1104-participant cohort random sample. Cox models that adjusted for Framingham stroke risk factors were used to assess the association of blood type with stroke.

RESULTS

During 5.8 years of follow-up, blood types A or B vs. type O were not associated with stroke. Blood type AB vs. O was associated with an increased risk of stroke (adjusted hazard ratio [HR] 1.83, 95% confidence interval [CI] 1.01-3.30). The association of blood type AB vs. O was greater in those without diabetes (adjusted HR 3.33, 95% CI 1.61-6.88) than those with diabetes (adjusted HR 0.49, 95% CI 0.17-1.44) (P interaction = 0.02). Factor VIII levels accounted for 60% (95% CI 11%-98%) of the association of AB blood type and stroke risk.

CONCLUSION

Blood type AB is associated with an increased risk of stroke that is not attenuated by conventional stroke risk factors, and factor VIII levels were associated with 60% of the association. While blood type AB is rare in the US population, it is a significant stroke risk factor and may play an important role in stroke risk in these individuals.

Transfusion support of autoimmune hemolytic anemia: how could the blood group genotyping help?

Conventional pretransfusion testing based on hemagglutination assays can be challenging for patients with autoimmune hemolytic anemia (AIHA) because of the presence of auto-antibodies. It has been suggested that deoxyribonucleic acid-based methods could be more efficient in the selection of antigen-matched red blood cell units in those settings. Because of the high risk of alloimmunization of these patients and the labor-intensive nature of adsorption techniques, we decided to evaluate the feasibility of selecting antigen-matched units on the basis of RBC genotyping. We included in our routine RBC genotyping program samples from 7 patients with AIHA presenting a strongly positive direct antiglobulin test. This made the routine compatibility tests difficult. Most patients had previously received transfusions because of warm AIHA. Matched donor units were selected according to the genotype. For all but 1 patient, blood group genotyping could be done on time to allow antigen-matched transfusion. Four patients received antigen-matched red blood cell units based on RBC genotyping and for 1 patient the fact that no matched units were available led us to postpone the transfusion. After each transfusion, the recovery was recorded and considered satisfactory for all transfused patients.

Molecular approaches to transfusion medicine in Polynesians and Maori in New Zealand

In recent years, with the application of genotyping technology, there has been a substantial increase in the number of reported blood group alleles. This survey was designed to evaluate new molecular blood group genotyping methods and compile reference blood group data sets for Polynesian and Maori subjects. Subsequent analyses of these results were used to calculate probability of random match, to trace Polynesian ancestry and migration patterns and to reveal past and present episodes of genetic admixture. Genomic DNA samples from Maori and Polynesian subjects were drawn from the Victoria University of Wellington DNA Bank and genotyped using combination of commercial PCR-SSP kits, hybridization SNP assay services or sequence-based typing. This survey also involves compilation of serological ABO and Rhesus blood group data from RakaiPaaka Iwi tribal members for comparison with those generated during our molecular blood group study. We observed perfect consistency between results obtained from all molecular methods for blood group genotyping. The A, O, DCcEe, DCCee, MNs, K-k+, Jk(a+b-), Jk(a+b+), Fy(a+b-), Fy(a+b+), Di(a+b-), Co(a+b-) and Do(a-b+) were predominant blood group phenotypes in both Polynesians and Maori. Overall, our survey data show only small differences in distributions of blood group phenotypes between Polynesian and Maori groups and their subgroups. These differences might be associated with selection, population history and gene flow from Europeans. In each case, we estimate that patients with certain blood groups have a very low probability of an exact phenotypic match, even if the patients were randomly transfused with blood from donors of their own ethnicity. The best way to avoid haemolytic transfusion reaction in such cases is to perform a pretransfusion cross-match and recruit increased numbers of donors with rare phenotype profiles. The conclusion of this study is that application of molecular method covering as many known variants as possible may help to improve the accuracy blood group genotyping and potentially conserve the routine requirements of transfusion centres.

Ideal donors, imperfect results in sickle cell disease

In this issue of Blood, Chou et al report findings from an observational study of alloimmunization in patients with sickle cell disease (SCD) receiving blood transfusions from ethnically matched donors.

Red blood cell alloimmunization in sickle cell disease and in thalassaemia: current status, future perspectives and potential role of molecular typing

Red blood cell (RBC) transfusions are a milestone in the treatment for sickle cell anaemia (SSA) and for thalassaemia. RBC alloimmunization remains a major challenge of chronic transfusion therapy, and it can lead to adverse life-threatening events. The alloimmunization risk could depend on multiple factors such as the number of transfusions and, most of all, the genetic background. Different ethnic groups are predisposed to immunization because of a significant degree of RBC antigenic mismatch between donor and recipient. There is no universal agreement and standards for the most appropriate selection of RBC units in chronically transfused subjects. Current practice only deals with compatibility of ABO, Rh and K antigens. Molecular RBC antigenic matching extended to other blood group systems is an innovative strategy to ensure a better quality and effectiveness of transfusion therapy.