Emerging strategies of blood group genotyping for patients with hemoglobinopathies

Low-cost molecular methodology for blood group antigens identification and genotyping contribution to transfusion efficacy in multiple transfused patients

BACKGROUND

Blood transfusions usually result in the production of alloantibodies, complicating subsequent transfusions. Many blood group systems, in addition to ABO and Rh, can lead to the production of irregular antibodies in multiple transfused patients.

OBJECTIVES

The aim of this work was to standardize a molecular biology methodology for identified some alleles of KEL, FY, JK and DI blood group system; the transfusion efficacy of chronically transfused patients with phenotype-matched blood was also evaluated.

METHODS

A PCR-SSP was developed and validated using Sanger sequencing. The genotype and frequencies of 141 multiple transfused patients treated at blood banks of Maringá were compared with the blood donor's population to assess the availability of compatible blood bags. The clinical history of 29 patients on a phenotype-compatible transfusion regimen was followed to assess pre- and post-genotyping alloimmunization.

RESULTS

The PCR-SSP was effective in identifying the genotypes under study. Significant differences were observed in genotype and allele frequencies for FY and JK. Compatible bags were identified for all patients. Most patients (93.1%) did not develop new alloantibodies after erythrocyte genotyping.

CONCLUSION

Erythrocyte genotyping proved to be important both in the search for positive blood bags for rare alleles and in the prevention of alloimmunization.

SLC44A2 Frequency, a New TaqMan Real-Time Polymerase Chain Reaction Method for HNA-3A/3B Genotyping, and a New Application of Droplet Digital PCR

Background: Human neutrophil antigen-3A (HNA-3A) and human neutrophil antigen-3B (HNA-3B) are generated by a single-nucleotide polymorphism (rs2288904, c.461G > A) in exon 7 of the choline transporter-like protein-2 gene (CTL2, also known as SLC44A2). Antibodies to HNA-3 can be generated following blood transfusion or other factors resulting in exposure to HNA-3 antigens. These antibodies can cause transfusion-related acute lung injury (TRALI) or neonatal alloimmune neutropenia (NAIN). This study describes a sensitive and specific TaqMan real-time polymerase chain reaction (PCR) method to screen for the HNA-3 genotype using specific primers and probes designed to detect allelic polymorphisms. Considering the high sensitivity and accuracy of droplet digital PCR (ddPCR) in the identification of the rare SLC44A2*2 allele, we used this technique to identify blood donors with the rare HNA-3B antigen and calculate the allele frequency of SLC44A2 in mixed populations with different proportions.

Methods: DNA samples purified from 208 donors in northwest China were subjected to TaqMan real-time PCR to detect allelic polymorphisms in SLC44A2. The results were confirmed by Sanger sequencing. The rare HNA-3B antigen was detected by ddPCR. SLC44A2 frequency was determined by two-channel ddPCR.

Results: The genotypes of all DNA samples were detected by the TaqMan real-time PCR using specific probes for HNA-3, and the results were consistent with the Sanger sequencing results in respect to the HNA-3A and HNA-3B polymorphisms. The allele frequencies of SLC44A2*1 and SLC44A2*2 in the 208 donors in northwest China were 64.9% (95% confidence interval [CI], 59%–70.8%) and 35.1% (95% CI, 29.2%–41%), respectively. The ratio of SLC44A2*2 alleles was accurately detected in all blood pools by ddPCR but not by TaqMan real-time PCR. This allowed for the SLC44A2 frequency in the population to be accurately inferred.

Conclusion: This new method of detecting SLC44A2 alleles was highly sensitive and specific, as confirmed by Sanger sequencing. ddPCR using the designed probes resulted in successful detection of the rare HNA-3B antigen. Furthermore, we successfully detected the rare HNA-3B antigen and inferred the SLC44A2 frequency by ddPCR using the probes that we designed.

Next-generation sequencing of 35 RHD variants in 16 253 serologically D- pregnant women in the Finnish population

Fetal RHD screening for targeted routine antenatal anti-D prophylaxis has been implemented in many countries, including Finland, since the 2010s. Comprehensive knowledge of the RHD polymorphism in the population is essential for the performance and safety of the anti-D prophylaxis program. During the first 3 years of the national screening program in Finland, over 16 000 samples from RhD- women were screened for fetal RHD; among them, 79 samples (0.5%) containing a maternal variant allele were detected. Of the detected maternal variants, 35 cases remained inconclusive using the traditional genotyping methods and required further analysis by next-generation sequencing (NGS) of the whole RHD gene to uncover the variant allele. In addition to the 13 RHD variants that have been previously reported in different populations, 8 novel variants were also detected, indicating that there is more variation of RHD in the RhD- Finnish population than has been previously known. Three of the novel alleles were identified in multiple samples; thus, they are likely specific to the original Finnish population. National screening has thus provided new information about the diversity of RHD variants in the Finnish population. The results show that NGS is a powerful method for genotyping the highly polymorphic RHD gene compared with traditional methods that rely on the detection of specific nucleotides by polymerase chain reaction amplification.

Blood group genotyping in alloimmunized multi-transfused thalassemia patients from Iran

Objectives

Serological methods may not be reliable for RBC antigen typing, especially in multi‐transfused patients. The blood group systems provoking the most severe transfusion reactions are mainly Rh, Kell, Kidd, and Duffy. We intended to determine the genotype of these blood group system antigens among Iranian alloimmunized thalassemia patients using molecular methods and compare the results with serological phenotyping.

Methods

Two hundred patients participated in this study. Blood group phenotype and genotype were determined using the serological method and PCR‐SSP, respectively. The genotypes of patients with incompatibility between phenotype and genotype were re‐evaluated by RFLP‐PCR and confirmed by DNA sequencing.

Results

Discrepancies between phenotype and genotype results were found in 132 alleles and 83 (41.5%) patients; however, there was complete accordance between the three genotyping methods. Most discrepancies were detected in Rh and Duffy systems with 47 and 45 cases, respectively, and the main discrepancy was in the FY*B/FY*B allele when serologically showed Fy(a+b+). All 39 undetermined phenotypes, due to mixed‐field reactions, were resolved by molecular genotyping.

Conclusion

Molecular genotyping is more reliable compared with the serological method, especially in multi‐transfused patients. Therefore, the addition of blood group genotyping to serological assays can lead to an antigen‐matched transfusion in these patients.

Genomic analyses of KEL alleles in alloimmunized thalassemia patients from Iran

OBJECTIVES

Serological methods are unreliable for red blood cells (RBCs) antigen typing in multi-transfused thalassemia patients due to the presence of donor RBCs in the recipient's circulation and interfering antibodies. Kell blood group system is important in transfusion medicine and Kell antibodies have shown as the most prevalent antibodies in thalassemia patients. We intended to determine the genotype of Kell antigens among Iranian alloimmunized thalassemia patients using molecular methods and compare the results with serological phenotyping.

METHODS

Two hundred thalassemia patients participated in this study. Blood group phenotype was performed by the serological method, while the genotype was determined for KEL*01, KEL*02, KEL*03, and KEL*04 alleles using PCR-Sequence Specific Primer (PCR-SSP) method. The genotypes of patients with incompatibility between phenotype and genotype were re-evaluated by Restriction Fragment Length Polymorphism-PCR (RFLP-PCR) and confirmed by DNA sequencing in all cases.

RESULTS

Ten patients were found with discrepancies between genotype and phenotype; however, there was a complete agreement between the results of SSP-PCR, RFLP-PCR, and DNA sequencing. Six discrepancies were found in the KEL*01/KEL*02 allele when serologically phenotyped as K-k+. One patient with K-k- and three patients with Kpa-Kpb + phenotype were identified as KEL*01/KEL*02 and KEL*03/KEL*04, respectively.

CONCLUSION

It can be concluded that molecular genotyping is more reliable compared with the serological method, especially in the patients who have received multiple transfusions. Therefore, using a combination of these techniques can lead to a better matched transfusion in these patients.

Molecular Blood Group Screening in Donors from Arabian Countries and Iran Using High-Throughput MALDI-TOF Mass Spectrometry and PCR-SSP

Background and Aims

Only little is known about blood groups other than ABO blood groups and Rhesus factors in Arabian countries and Iran. During the last years, increased migration to Central Europe has put a focus on the question how to guarantee blood supply for patients from these countries, particularly because hemoglobinopathies with the need of regular blood support are more frequent in patients from that region. Therefore, blood group allele frequencies should be determined in individuals from Arabian countries and Iran by molecular typing and compared to a German rare donor panel.

Methods

1,111 samples including 800 individuals from Syria, 147 from Iran, 123 from the Arabian Peninsula, and 41 from Northern African countries were included in a MALDI-TOF MS assay to detect polymorphisms coding for Kk, Fy(a/b), Fy_null, C_w, Jk(a/b), Jo(a+/a-), Lu(a/b), Lu(8/14), Ss, Do(a/b), Co(a/b), In(a/b), Js(a/b), Kp(a/b), and variant alleles RHCE*c.697C>G and RHCE *c.733C>G. Yt(a/b), S-s-U-, Vel_null, Co_null, and RHCE *c.667G>T were tested by PCR-SSP.

Results

Of the Arabian donors, 2% were homozygous for the FY *02.01N allele (Fy_null), and 15.7% carried the heterozygous mutation. However, 0.8% of the German donors also carried 1 copy of the allele. 3.6% of all and 29.3% of Northern African donors were heterozygous for the RHCE *c.733C>G substitution, 0.4% of the Syrian probands were heterozygous for DO *01/DO *01.-05, a genotype that was lacking in German donors. Whereas the KEL *02.06 allele coding for the Js(a) phenotype was missing in Germans; 0.8% of the Syrian donors carried 1 copy of this allele. 1.8% of the Syrian but only 0.3% of the German donors were negative for YT *01. One donor from Northern Africa homo-zygously carried the GYPB *270+5g>t mutation, inducing the S-s-U+^w phenotype, and in 2 German donors a GYPB *c.161G>A exchange, which induces the Mit+ phenotype, caused a GYPB *03 allele dropout in the MALDI assay. The overall failure rate of the Arabian panel was 0.4%.

Conclusions

Some blood group alleles that are largely lacking in Europeans but had been described in African individuals are present in Arabian populations at a somewhat lower frequency. In single cases, it could be challenging to provide immunized Arabian patients with compatible blood.

Validation of the Accuracy of Self-Reported ABO Blood Types in the Japan Nurses’ Health Study

Background: The associations between ABO blood type and risk of diseases including cancer have been reported from epidemiological studies. Self-reporting is one of the most widely used methods of collecting the ABO blood type information. Verifying the accuracy of self-reporting is important to consider measurement errors. We aimed to conduct validation of self-reported ABO blood types in the Japan Nurses’ Health Study (JNHS), which is a large prospective cohort study. Methods: The concordance rate between self-reported and serologically or genetically inferred ABO blood groups was investigated for a subsample of 41 subjects from the Gunma Nurses’ Health Study, which was a pilot cohort study that preceded the JNHS. The presence of antibodies to A or B antigens in serum (serological test) and allele types of the ABO gene (genotyping test) were determined by using frozen blood samples that were preserved for approximately 7 years. ABO blood types were determined from these tests and compared with self-reported data. Results: All of the nurses reported that their ABO blood groups were concordant with those determined by a serological and/or genotyping test. Self-reported ABO blood types of 35 of 38 (92.1%) participants were consistent with the results from serological typing, while the answers of three participants were not. In these three participants, ABO genotypes that were inferred from genotyping of three single nucleotide polymorphisms in ABO loci perfectly matched with their self-reported ABO types, and all of these were O-type. Conclusions: Japanese health professionals report their blood type with a high degree of accuracy. Special attention should be paid to the O-type group in serological analysis of blood samples that have been preserved for several years in longitudinal studies.

Assessment of common red blood cell pretreatments to yield an accurate serologic antigen phenotype compared with genotype-predicted phenotype

For patients requiring multiple transfusions and patients with positive direct antiglobulin tests (DATs), an extended red blood cell (RBC) phenotype can provide valuable information and help to determine the risk of forming alloantibodies. In some instances, the phenotype may be used for prophylactic matching. Phenotyping in this patient population is often hindered by the presence of circulating donor cells and/or by a positive DAT. Several methods, such as EDTA glycine acid (EGA) treatment to remove IgG, hypotonic saline wash to separate autologous RBCs, or reticulocyte separation, are often used in these situations to isolate patient RBCs for serologic phenotyping. This study aimed to determine the accuracy of each RBC pretreatment method by comparing serologically determined antigen types with those predicted by RBC genotyping. Forty-eight peripheral blood samples from recently transfused patients were phenotyped for selected antigens in the Rh, Kell, MNS, Duffy, and Kidd systems. Treatment methods for the sample sets were reticulocyte separation (N = 12), EGA (N = 16), and hypotonic saline wash (N = 20). DNA was extracted using standard methods, and genotyping was performed using the HEA BeadChip panel. In addition, 21 samples positive for RBC-bound IgG were EGA-treated up to two times. These samples were analyzed pre- and post-EGA treatment for RBC-bound IgG by tube DAT and by flow cytometry with fluorescein isothiocyanate-labeled anti-human IgG. After reticulocyte separation, 3 of the 12 samples had discordant types with one antigen each: Fy^b, N, and K; serologic results were negative compared with genotype-predicted positive phenotype results. The EGA-treated sample set showed one discordant type: Fy^b; serologic results were negative compared with genotype-predicted positive phenotype results. Four of the 20 samples had discordant types involving the following antigens: Fy^b, N, e, and M; serologic results were negative compared with genotype-predicted positive phenotype results. After EGA treatment of 21 samples, 14 (67%) were negative for RBC-bound IgG by tube DAT, and 7 remained positive. Using flow cytometry, EGA treatment rendered only 4 samples negative, and 17 remained positive. In the antigen testing sample set of 48 samples, 10 of 511 total antigen types tested were discordant. Discordant types were most frequent in the hypotonic saline wash sample set (N = 6). In the flow cytometry sample set, 48 percent of the samples negative by tube DAT after EGA elution had detectable RBC-bound IgG by flow cytometry. These findings suggest that caution should be taken when using phenotype results from all pretreated RBCs and support the use of RBC genotyping to predict RBC antigen expression in samples from recently transfused patients.

For patients requiring multiple transfusions and patients with positive direct antiglobulin tests (DATs), an extended red blood cell (RBC) phenotype can provide valuable information and help to determine the risk of forming alloantibodies. In some instances, the phenotype may be used for prophylactic matching. Phenotyping in this patient population is often hindered by the presence of circulating donor cells and/or by a positive DAT. Several methods, such as EDTA glycine acid (EGA) treatment to remove IgG, hypotonic saline wash to separate autologous RBCs, or reticulocyte separation, are often used in these situations to isolate patient RBCs for serologic phenotyping. This study aimed to determine the accuracy of each RBC pretreatment method by comparing serologically determined antigen types with those predicted by RBC genotyping. Forty-eight peripheral blood samples from recently transfused patients were phenotyped for selected antigens in the Rh, Kell, MNS, Duffy, and Kidd systems. Treatment methods for the sample sets were reticulocyte separation (N = 12), EGA (N = 16), and hypotonic saline wash (N = 20). DNA was extracted using standard methods, and genotyping was performed using the HEA BeadChip panel. In addition, 21 samples positive for RBC-bound IgG were EGA-treated up to two times. These samples were analyzed pre- and post-EGA treatment for RBC-bound IgG by tube DAT and by flow cytometry with fluorescein isothiocyanate–labeled anti-human IgG. After reticulocyte separation, 3 of the 12 samples had discordant types with one antigen each: Fy^b, N, and K; serologic results were negative compared with genotype-predicted positive phenotype results. The EGA-treated sample set showed one discordant type: Fy^b; serologic results were negative compared with genotype-predicted positive phenotype results. Four of the 20 samples had discordant types involving the following antigens: Fy^b, N, e, and M; serologic results were negative compared with genotype-predicted positive phenotype results. After EGA treatment of 21 samples, 14 (67%) were negative for RBC-bound IgG by tube DAT, and 7 remained positive. Using flow cytometry, EGA treatment rendered only 4 samples negative, and 17 remained positive. In the antigen testing sample set of 48 samples, 10 of 511 total antigen types tested were discordant. Discordant types were most frequent in the hypotonic saline wash sample set (N = 6). In the flow cytometry sample set, 48 percent of the samples negative by tube DAT after EGA elution had detectable RBC-bound IgG by flow cytometry. These findings suggest that caution should be taken when using phenotype results from all pretreated RBCs and support the use of RBC genotyping to predict RBC antigen expression in samples from recently transfused patients.

Clinical outcome of transfusions with extended red blood cell matching in β-thalassemia patients: A single-center experience

BACKGROUND

The development of alloantibodies may complicate the management of patients with β-thalassemia. An extended antigenic matching may reduce the risk of alloimmunization. Our previous study showed that the introduction of molecular red blood cell (RBC) typing allows finding suitable blood units for multi-transfused patients. The aim of this study was to evaluate the benefit of RBC transfusion with extended antigenic match.

MATERIALS AND METHODS

At the University of Campania "L. Vanvitelli", we selected β-thalassemia major patients (age ≤23 years), without preformed alloantibodies. Data of patients receiving transfusion of leukoreduced RBC units for a period of one year with partial better match (PBM) including ABO, RhD, C/c, E/e, K/k antigens and consecutive one year with extended match (EM) including ABO, RhD, C/c, E/e, K/k, Fy^a/Fy^b, Jk^a/Jk^b, M/N, S/s antigens, were compared.

RESULTS

Eighteen patients, 8 males and 10 females with a mean age of 15.4 years (6.4 SD) received a mean number of 41.2 (6.0 SD) RBC units transfused with PBM and 41.8 (6.2 SD) with EM protocols. After two years of RBC transfusions with both antigen matching protocols, no new alloantibodies were developed in patients. No significant differences in Hb concentration and volume of RBC transfused were found between PBM and EM protocols.

CONCLUSIONS

Thalassemia patients may benefit from receiving RBC transfusions based on extended antigen matching as demonstrated by the lack of new alloantibodies. However, our data show a high concordance between PBM and EM protocols considering pre-transfusion Hb, increment of Hb and volume of RBC transfused.

Establishment and Utilization of a Transfusion Recipient Registry in Korea: Estimating the Frequencies of Specific Antigen-Negative Blood Units

OBJECTIVES

This study was conducted to establish the Korean national registry, to evaluate the distribution of unexpected antibodies, and to determine the frequencies of specific antigen-negative blood units.

METHODS

Data added to the Korean national registry between July 2013 and April 2016 were analyzed. The distribution of unexpected antibodies and frequencies of specific antigen-negative blood units were estimated.

RESULTS

In total, 3,513 cases from 22 institutes were registered. The most common single alloantibodies were anti-E, anti-Lea, and anti-M. The most common multiple alloantibodies were anti-E with anti-c, anti-C with anti-e, and anti-Lea with anti-Leb. The frequencies of E-, Lea-, and M-negative units were 42.3%, 56.9%, and 20.2%, respectively.

CONCLUSIONS

The distribution of unexpected antibodies and frequencies of specific antigen-negative blood units were investigated using data from the Korean national registry. The results provide useful data to predict the number of blood units to be tested to obtain compatible blood units.

Multiplex Lateral Flow Assay for Rapid Visual Blood Group Genotyping

Conventional blood group phenotyping by hemagglutination assays, carried out pretransfusion, is unsuitable in certain clinical situations. Molecular typing offers an alternative method, allowing the deduction of blood group phenotype from genotype. However, current methods require a long turnaround time and are not performed on-site, limiting their application in emergency situations. Here, we report the development of a novel, rapid multiplex molecular method to identify seven alleles in three clinically relevant blood group systems (Kidd, Duffy, and MNS). Our test, using a dry-reagent allele-specific lateral flow biosensor, does not require DNA extraction and allows easy visual determination of blood group genotype. Multiplex linear-after-the-exponential (LATE)-PCR and lateral flow parameters were optimized with a total processing time of 1 h from receiving the blood sample. Our assay had a 100% concordance rate between the deduced and the standard serological phenotype in a sample from 108 blood donors, showing the accuracy of the test. Owing to its simple handling, the assay can be operated by nonskilled health-care professionals. The proposed assay offers the potential for the development of other relevant single nucleotide polymorphism (SNP) panels for immunohematology and new applications, such as for infectious diseases, in the near future.