Primary anti-D alloimmunization induced by "Asian type" RHD (c.1227G>A) DEL red cell transfusion

Guide to Rho(D) Immune Globulin in Women With Molecularly Defined Asian-type DEL (c.1227G>A)

Rh hemolytic disease of the fetus and newborn is a potential risk for D-negative mothers who produce anti-D during pregnancy, which can lead to morbidity and mortality in subsequent pregnancies. To prevent this hemolytic disease, Rho(D) immune globulin (RhIG) is generally administered to D-negative mothers without anti-D at 28 weeks of gestation and shortly after delivery. However, current guidelines suggest that pregnant mothers with molecularly defined weak D types 1, 2, 3, 4.0, and 4.1 do not need RhIG as they are unlikely to produce alloanti-D when exposed to fetuses with D-positive red cells. This issue and the necessity of RHD genotyping have been extensively discussed in Western countries, where these variants are relatively common. Recent evidence indicates that women with Asian-type DEL (c.1227G>A) also do not form alloanti-D when exposed to D-positive red cells. We report that mothers with molecularly defined Asian-type DEL, similar to those with weak D types 1, 2, 3, 4.0, and 4.1, do not require RhIG before and after delivery. Collectively, this review could pave the way for the revision of international guidelines to include the selective use of RhIG based on specific genotypes, particularly in women with the Asian-type DEL.

Two Cases of Anti-D Alloimmunization in D-Negative Thai Patients as a Result of the Asian-Type DEL on Transfused Red Cells

Introduction

DEL is known to be one of the weakest D variants, which can be detected by the adsorption-elution technique or by molecular study. Currently, in Thailand, we do not routinely test for DEL variants serologically or genetically among serologic RhD-negative blood donors.

Case Presentation

We reported 2 cases of alloimmunization after transfused with Rh DEL, RHD*DEL1 allele, in the Thai population. The first case was a 73-year-old male with anemia who presented with post-cardiac arrest and septic shock. The patient was group B, RhD-negative, and was transfused with RhD-negative red blood cells (RBCs). Antibody screening and identification found that the patient developed anti-D and anti-Mia during the admission course. The second case was a 38-year-old woman with pseudomyxoma peritonei who developed anti-D after receiving four units of RhD-negative RBCs during cytoreductive surgery with hyperthermic intraperitoneal chemotherapy. Both patients did not receive anti-D immunoglobulin and had no previous history of anti-D detection. We retrospectively investigated and found two units of RHD*DEL1 among the RBCs transfused to these patients.

Discussion

Previous reports of several cases of anti-D alloimmunization in RhD-negative recipients transfused by RHD*DEL1, an Asian-type DEL, are limited only to East Asia. We first identified 2 patients with anti-D alloimmunization after receiving the RHD*DEL1 RBCs in the Thai population. This raises concern about Rh DEL screening among D-negative Thai blood donors and whether to remove DEL units from the D-negative inventory to improve patient safety.

DEL phenotype in RhD-negative North Indian blood donors

BACKGROUND

Rh-DEL type is not detected on routine serology and requires specialized adsorption elution methods which are laborious. Identifying the DEL phenotype in blood donors is important to prevent alloimmunization in transfusion recipients. The present study aimed to determine the frequency of DEL phenotype in RhD-negative North Indian blood donors and correlate the results with Rh Cc/Ee phenotype.

MATERIALS AND METHODS

In this prospective descriptive cross-sectional study, a total of 205 blood donors with historic blood group RhD-negative were enrolled. All samples were subjected to blood grouping using a fully automated immunohematology analyzer and samples that typed as RhD negative by two different anti-D antisera were tested for Weak D. Weak D-negative samples were subjected to adsorption and elution for DEL phenotype. All samples were also tested for extended Rh phenotype for C/c and E/e antigens.

RESULTS

Of the total 11934 donors during the study, 6.2% (n = 743) donors were RhD negative. Of the 205 donors enrolled in the study, two donor samples were serologically weak D positive. None of the remaining 203 donors tested positive for the DEL phenotype. The extended Rh phenotype performed for these donors showed that 6.83% (n = 14) donors were positive for RhC antigen and 1.46% (n = 3) were positive for Rh E antigen. Both weak D-positive donors were also positive for the Rh C antigen.

CONCLUSION

The prevalence of DEL phenotype is low in the Indian population and studies with larger sample sizes are required to determine the effectiveness of routine C/E typing as a strategy to identify DEL-positive individuals.

Genotype analysis to clarify RhD variants in discrepant samples of Chilean population

Introduction

The D antigen variants are classified as weak, partial, and extremely weak (DEL) and can be differentiated using molecular tests. In Chile, the laboratories of local blood centers do not identify variants of the D antigen, referring them for study to the Reference Laboratory of the Public Health Institute of Chile. So, our aim was to talk about the results of the molecular analysis of variants of the D antigen in samples that had different results in the serological classification.

Methods

In the D antigen classification of the Rh system, 479 samples with serological discrepant results were sent for molecular analysis. The Rh phenotype was performed with monoclonal anti-C, anti-c, anti-E, and anti-e antisera by direct agglutination. To find the D antigen, researchers used direct agglutination with monoclonal antisera and indirect antiglobulin testing with the column (gel) agglutination method. Molecular analysis was performed with a polymerase chain reaction with sequence-specific primers (SSP-PCR) and sequencing.

Results and discussion

The presence of D antigen variants was confirmed in 332 samples (69.3%), with an initial discrepancy in serological classification. In this group of discrepant samples, the frequency of weak RhD variants was 66% (219/332), that of extremely weak RhD was 28% (93/332), and that of partial RhD was 6% (20/332). The weak variants type 2 (27.4%), type 3 (8.4%), type 48 (8.4%), and type 1 (8.1%) were the next most prevalent variants after RHD*DEL43 (28%). The ccEe (R2r) phenotype was the most frequently detected (38.4%) and is present in 87% of the RHD*DEL43 samples. The E antigen is associated with the presence of this variant. Our analyses give the first description of D antigen variants in Chile. The most common variants are DEL type (RHD*DEL43) and weak (weak type 2), which are linked to the ccDEe (R2r) phenotype. These findings allow us to characterize the variants of the D antigen in Chile and, according to the obtained data, to design strategies for the management of donors, patients, and pregnant women.

Anti-D alloimmunization by Asia type DEL red blood cell units in a D-negative Thai patient

BACKGROUND

DEL phenotype is a rare Rh variant that cannot be detected by routine serological typing, and DEL individuals are thus typed D-negative (D-). Anti-D alloimmunization has been reported in "true" D- patients receiving DEL red blood cells (RBCs).

CASE PRESENTATION

A 17-year-old, D- Thai male patient suffering from immunodeficiency syndrome with negative antibody screening received RBC units from 17 serological D- donors over a period of seven months due to acute respiratory failure with anemia. Before the 12th transfusion, anti-D production was detected. He was later transfused with RBCs from six other apparent D- donors. In order to elucidate anti-D production, all 17 blood donors were investigated by replicative serological testing and molecular analysis to identify potential RHD gene variants. All donors were confirmed D- by routine method, but as many as 12/17 were positive by adsorption-elution testing. Molecular analysis showed that five donors, including four whose blood was transfused before anti-D production occurred, carry the Asia type DEL allele, and are thus predicted to express a DEL phenotype. These data clearly suggest that 1/ the alloimmunized D- patient was exposed to D antigen, 2/ our adsorption-elution test is currently defective to identify DEL RBCs, and 3/ molecular analysis is highly valuable for Asia type DEL allele screening.

CONCLUSION

For the first time in Thailand, we report anti-D alloimmunization in a serological D- patient transfused by Asia type DEL RBC units. This work definitely supports the implementation of a dedicated policy for DEL blood management including molecular testing.

DEL variants: review of molecular mechanisms, clinical consequences and molecular testing strategy

Patients with DEL phenotype, a D variant with a low number of D antigens per red blood cell, are routinely typed as RhD-negative in serology testing and are detectable only by adsorption and elution techniques or molecular methods. DEL is of clinical importance worldwide, as indicated by its genotype-phenotype discrepancies among different populations and its potential to cause anti-D alloimmunization when DEL phenotype individuals are inadvertently managed as RhD-negative. This narrative review summarized the DEL alleles causing DEL phenotype and the underlying mechanisms. The clinical consequences and current molecular testing approach were discussed to manage the transfusion needs of patients and donors with DEL phenotype.

The Significance of RHD Genotyping and Characteristic Analysis in Chinese RhD Variant Individuals

Background

RhD is the most important and complex blood group system because of its highly polymorphic and immunogenic nature. RhD variants can induce immune response by allogeneic transfusion, organ transplantation, and fetal immunity. The transfusion strategies are different for RhD variants formed by various alleles. Therefore, extensive investigation of the molecular mechanism underlying RhD variants is critical for preventing immune-related blood transfusion reactions and fetal immunity.

Methods

RhD variants were collected from donors and patients in Zhejiang Province, China. The phenotypes were classified using the serologic method. The full coding regions of RHD gene were analyzed using the PCR-SBT method. The multiplex ligation-dependent probe amplification (MLPA) assay was used to analyze the genotype and gene copy number. SWISS-MODLE and PyMOL software were used to analyze 3D structures of RhD caused by the variant alleles. The effect of non-synonymous substitutions was predicted using Polymorphism Phenotyping algorithm (PolyPhen-2), Sorting Intolerant From Tolerant (SIFT), and Protein Variation Effect Analyzer (PROVEAN) software.

Results

In the collected RhD variants, 28 distinct RHD variant alleles were identified, including three novel variant alleles. RH-MLPA assay is advantageous for determining the copy number of RHD gene. 3D homology modeling predicted that protein conformation was disrupted and may explain RhD epitope differential expression. A total of 14 non-synonymous mutations were determined to be detrimental to the protein structure.

Discussion

We revealed the diversity of RHD alleles present in eastern Chinese RhD variants. The bioinformatics of these variant alleles extended our knowledge of RhD variants, which was crucial for evaluating their impact to guide transfusion support and avoid immune-related blood transfusion reactions.

A practical and effective strategy in East Asia to prevent anti-D alloimmunization in patients by C/c phenotyping of serologic RhD-negative blood donors

Serologic RhD‐negative red cells can cause anti‐D alloimmunization if they carry the Asian‐type DEL or other DEL variants. RHD genotyping is a viable countermeasure if available, but inexpensive alternatives are worthy of consideration. RhD‐negative blood donors in Japan were studied by anti‐D adsorption‐elution and RHD genotyping. We collated published case reports of RhD‐negative red cell transfusions associated with inexplicable anti‐D immunization. Of 2754 serologic RhD‐negative donors, 378 were genotyped D/d. Anti‐D adsorption‐elution revealed 63.5% (240 of 378) to be DEL, of whom 96.7% (232 of 240) had the 1227G > A variant, diagnostic for the Asian‐type DEL. All 240 donors also carried at least one C antigen; none had a cc phenotype. The chance of transfusing DEL red cells to genuinely RhD‐negative Asian patients (based on a three‐unit transfusion) ranges from 16.7% in Korea to 69.4% in Taiwan, versus 0.6% in Germany. Among 22 RhD‐negative recipients of serologic RhD‐negative red cells, who produced new or increased anti‐D antibody titers, all 17 from East Asia were transfused with red cells with a C‐positive phenotype or known to be Asian‐type DEL or both. Serologic RhD‐negative East Asians with a cc phenotype can be red cell donors for RhD‐negative recipients, especially those of childbearing potential.

Antibodies to Low-Copy Number RBC Alloantigen Convert a Tolerogenic Stimulus to an Immunogenic Stimulus in Mice

Red blood cells expressing alloantigens are well known to be capable of inducing robust humoral alloantibody responses both in transfusion and pregnancy. However, the majority of transfusion recipients and pregnant women never make alloantibodies, even after repeat exposure to foreign RBCs. More recently, RBCs have been used as a cellular therapeutic-very much like transfusion, engineered RBCs are highly immunogenic in some cases but not others. In animal models of both transfusion and RBC based therapeutics, RBCs that do not induce an immune response also cause tolerance. Despite a robust phenomenology, the mechanisms of what regulates immunity vs. tolerance to RBCs remains unclear. However, it has been reported that copy number of alloantigens on the RBCs is a critical factor, with a very low copy number causing non-responsiveness (in both humans and mice) and also leading to tolerance in mice. Recently, we reported that an IgG2c specific for an RBC antigen can substantially enhance the humoral immune response upon transfusion of RBCs expressing that antigen. Herein, we report that an IgG2c converts RBCs with low antigen copy number from a tolerogenic to an immunogenic stimulus. These findings report the first known stimulus that induces humoral alloimmunization to a low copy number RBC alloantigen and identify a previously undescribed molecular switch that has the ability to affect responder vs. non-responder phenotypes of transfusion recipients.

Nation-wide investigation of RHD variants in Thai blood donors: Impact for molecular diagnostics

BACKGROUND

Knowledge of the molecular determinants driving antigen expression is critical to design, optimize, and implement a genotyping approach on a population-specific basis. Although RHD gene variability has been extensively reported in Caucasians, Africans, and East-Asians, it remains to be explored in Southeast Asia. Thus the molecular basis of non-D+ blood donors was investigated in Thailand.

STUDY DESIGN AND METHODS

First, 1176 blood samples exhibiting an inconclusive or negative result by automated serological testing were collected in the 12 Regional Blood Centres of the Thai Red Cross located throughout Thailand. Second, the RHD gene was analyzed in all samples by 1) quantitative multiplex PCR of short fluorescent fragments, and 2) direct sequencing, when necessary, for identifying structural variants and single nucleotide variants, respectively.

RESULTS

Additional serological typing yielded 51 and 1125 samples with weak/partial D and D-negative (D-) phenotype, respectively. In the first subset, partial RHD*06.03 was the most common variant allele (allele frequency: 18.6%). In the second subset, the whole deletion of the gene is largely the most frequent (allele frequency: 84.9%), followed by the Asian DEL allele found in 15.6% of the samples. Eight novel alleles with various mutational mechanisms were identified.

CONCLUSION

We report, for the first time at the national level, the molecular basis of weak/partial D and serologically D- phenotypes in Thai blood donors. The design and implementation of a dedicated diagnostic strategy in blood donors and patients are the very next steps for optimizing the management and supply of RBC units in Thailand.

Serological Detection of Rh-Del Phenotype among Rh-Negative Blood Donors at National Blood Center, Yangon, Myanmar

Background

Red cell Rhesus (Rh) antigen expression is influenced by the genetic polymorphism of RHD and RHCE genes and reveals serologically different reactions of RhD variants such as partial D, weak D, and Rh-Del. Serologically, Rh-Del type can only be detected by an adsorption-elution technique, and it might be mistyped as Rh-negative. The prevalence of Rh-Del has not been reported yet in Myanmar.

Method

A total of 222 Rh-negative blood donors in the National Blood Center were tested for weak D and Rh-Del by indirect antihuman globulin and adsorption-elution method, respectively. RhCE typing was performed among Rh-negative and Rh-Del.

Results

Of them, 75.2% (167/222) were Rh-negative, 15.8% (35/222) were Rh-Del, and 9% (20/222) were weak D. Of 202 blood donors (167 true Rh-negative and 35 Rh-Del), all of the Rh-Del positives were C-antigen-positive with 94.3% Ccee phenotype (33/35) and 5.7% CCee (2/35). Most of the Rh-negative donors (80.2%) were ccee phenotype (134/167).

Conclusion

About half of Rh-Del subjects were repeated donors, and attention was needed to avoid transfusion of truly Rh-negative patients to prevent alloimmunization. It is recommended to do Rh-Del typing of Rh-negative donors who are C-antigen-positive and consider moving them to the Rh-positive pool. Further study is needed to clarify the alloimmunization status for transfusion of Rh-Del blood to Rh-negative recipients. Molecular markers for RhD-negative and D variants should be established in the Myanmar population to improve selection of antisera for Rh typing and enhance safety of the transfusion services.

Characterization of RHD alleles present in serologically RHD-negative donors determined by a sensitive microplate technique

BACKGROUND AND OBJECTIVES

Weak D phenotypes with very low antigen densities and DEL phenotype may not be detected in RhD typing routine and could be typed as D-negative, leading to D alloimmunization of D-negative recipients. The present study aimed to investigate the presence of RHD-positive genotypes in blood donors typed as D-negative by an automated system using the solid-phase methodology as a confirmatory test.

METHODS

Two screenings were performed in different selected donor populations. For the first screening, we selected 1403 blood donor samples typed as D-negative regardless of the CE status, and in the second screening, we selected 517 donor samples typed as D-negative C+ and/or E+. RhD typing was performed by microplate in an automated equipment (Neo-Immucor®), and the confirmatory test was performed by solid-phase technique using Capture R® technology. A multiplex PCR specific to RHD and RHDψ was performed in a pool of 6 DNA samples. Sequencing of RHD exons was performed in all RHD-positive samples, and a specific PCR was used to identify the D-CE(4-7)-D hybrid gene.

RESULTS AND CONCLUSION

No weak D type was found in either screening populations. Additionally, 353 (18·4%) D-negative samples presented previously reported non-functional RHD genes, 2 samples had a DEL allele, and 6 samples demonstrated new alleles, including one novel DEL allele. Our study identified six new RHD alleles and showed that the inclusion of a confirmatory test using serological methodology with high sensitivity can reduce the frequency of weak D samples typed as D-negative.

Recommendations Regarding Practical DEL Typing Strategies for Serologically D-Negative Asian Donors

Background

DEL, the weakest D variant, is mistyped as D-negative by routine serological assays. Transfusion of red blood cells expressing the DEL phenotype has the potential to elicit anti-D alloimmunization in D-negative recipients. The goal of this study was to recommend DEL typing strategies for serologically D-negative Asian donors.

Methods

RhCE phenotyping and the adsorption-elution test were performed on 674 serologically D-negative samples. RHD genotyping using real-time polymerase chain reaction and melting curve analysis were also undertaken to identify DEL alleles. Costs and turnaround time of RhCE phenotyping, the adsorption-elution test, and RHD genotyping were estimated.

Results

Sensitivity and specificity of the adsorption-elution test for serologically D-negative samples were 94.9% (93/98) and 91.5% (527/576), respectively. C+ phenotypes were detected in all 98 samples with DEL alleles. Despite comparable costs, RHD genotyping was more accurate and rapid than the adsorption-elution test.

Conclusions

Two practical DEL typing strategies using RhCE phenotyping as an initial screening method were recommended for serologically D-negative Asian donors. Compared with DEL typing using RHD genotyping, serological DEL typing using adsorption-elution test is predicted to increase the incidence of anti-D alloimmunization and decrease the D-negative donor pool without having any cost-competitiveness but can be used in laboratories where molecular methods are not applicable.

Application of Multiplex Ligation-Dependent Probe Amplification Assay for Genotyping Major Blood Group Systems Including DEL Variants in the D-Negative Korean Population

Background

The DEL blood type, a very weak D variant, is a major concern in the field of transfusion medicine because of its potential to cause anti-D alloimmunization. We investigated the molecular basis of serologically D-negative phenotypes, including the DEL type, and the distribution of other blood group systems in the Korean population using the recently developed multiplex ligation-dependent probe amplification (MLPA) assay.

Methods

Blood group genotyping using the MLPA assay and RhCE phenotyping were performed on randomly selected 95 D-negative red blood cell products. The MLPA results were verified by multiplex PCR for the RHD promoter, exons 4, 7, and 10 and by direct sequencing of RHD exon 9.

Results

Out of 95 cases, total deletion of the RHD was observed in 74 cases (77.9%) and four cases (4.2%) had an RHD-CE-D hybrid allele. The other 17 cases (17.9%) had an RHD(1227G>A) allele, which was further confirmed by sequencing analysis. The RhCE phenotypes of RHD(1227G>A) alleles were composed of 14 Cce and 3 CcEe, and all 60 cases of the ce phenotype were revealed to have a total deletion of the RHD. Genotyping results and allele distribution of the other 17 blood group systems were consistent with previous reports on the East Asian population.

Conclusions

MLPA assay correctly determined RHD genotype, including RHD-CE-D hybrid alleles or RHD(1227G>A) allele, and other clinically relevant blood group genotypes in D-negative Koreans. The use of MLPA assay on serologically D-negative individuals may help improve transfusion safety by preventing anti-D alloimmunization.

Serological weak D phenotypes: a review and guidance for interpreting the RhD blood type using the RHD genotype

Approximately 0·2-1% of routine RhD blood typings result in a "serological weak D phenotype." For more than 50 years, serological weak D phenotypes have been managed by policies to protect RhD-negative women of child-bearing potential from exposure to weak D antigens. Typically, blood donors with a serological weak D phenotype have been managed as RhD-positive, in contrast to transfusion recipients and pregnant women, who have been managed as RhD-negative. Most serological weak D phenotypes in Caucasians express molecularly defined weak D types 1, 2 or 3 and can be managed safely as RhD-positive, eliminating unnecessary injections of Rh immune globulin and conserving limited supplies of RhD-negative RBCs. If laboratories in the UK, Ireland and other European countries validated the use of potent anti-D reagents to result in weak D types 1, 2 and 3 typing initially as RhD-positive, such laboratory results would not require further testing. When serological weak D phenotypes are detected, laboratories should complete RhD testing by determining RHD genotypes (internally or by referral). Individuals with a serological weak D phenotype should be managed as RhD-positive or RhD-negative, according to their RHD genotype.

DEL phenotype

DEL red blood cells (RBCs) type as D- by routine serologic methods and are transfused routinely, without being identified as expressing a very weak D antigen, to D- recipients. DEL RBCs are detected only by adsorption and elution of anti-D or by molecular methods. Most DEL phenotypes have been reported in population studies conducted in East Asia, although DEL phenotypes have been detected also among Caucasian individuals. Approximately 98 percent of DEL phenotypes in East Asians are associated with the RHD*DEL1 or RHD*01EL.01 allele. The prevalence of DEL phenotypes has been reported among D- Han Chinese (30%), Japanese (28%), and Korean (17%) populations. The prevalence of DEL phenotypes is significantly lower among D- Caucasian populations (0.1%). Among the 3-5 percent of African individuals who are D-, there are no reports of the DEL phenotype. Case reports from East Asia indicate that transfusion of DEL RBCs to D- recipients has been associated with D alloimmunization. East Asian immigrants constitute 2.1 percent of the 318.9 million persons residing in the United States, and an estimated 2.8 percent are blood donors. Using these statistics, we estimate that 68-683 units of DEL RBCs from donors of East Asian ancestry are transfused as D- annually in the United States. Given the reports from East Asia of D alloimmunization attributed to transfusion of DEL RBCs, one would expect an occasional report of D alloimmunization in the United States following transfusion of DEL RBCs to a D- recipient. If such cases do occur, the most likely reason that they are not detected is the absence of active post-transfusion monitoring for formation of anti-D.

Screening for DEL phenotype in RhD negative Indians

BACKGROUND

DEL phenotype represents a very weak form of D variant detected only by adsorption and elution technique. DEL phenotype individuals mistyped as RhD-negative can lead to alloimmunization after transfusion or pregnancy. Molecular techniques have now been used to identify DEL variants. They are commonly encountered in the East Asian population with RHD(K409K) being the most frequent allele. RHD(M295I) is the most common DEL allele in Caucasians. As there is a paucity of data on DEL phenotype in the Indian population, the study aims to screen RhD negative individuals for two most common DEL mutations.

MATERIAL AND METHODS

EDTA blood was collected from 900 RhD negative individuals. Serological analysis included testing for the five major Rh antigens- C, c, D, E, and e by tube technique. Samples showing negative reaction for the presence of D antigen by Indirect Antiglobulin test were further tested for DEL phenotype by adsorption and elution technique. Molecular analysis involved DNA extraction and testing by PCR-SSP for RHD(K409K) and RHD(M295I) DEL alleles.

RESULTS

Rh phenotyping showed 153 Rh negative individuals with r'r, ten with r''r and 737 with rr phenotype. All the samples tested negative for RhD antigen by adsorption and elution method. The two common DEL mutations RHD(K409K) and RHD(M295I) were also not detected in the study population.

CONCLUSION

The study population showed the absence of the two common DEL alleles, concluding the variant to be rare. A comprehensive study with a larger sample size to look for other DEL mutations should be performed.

[Genotyping of RhD-negative blood samples diagnosed by serological tests from patients waiting for kidney transplantation]

OBJECTIVE

To compare the accuracy of serological and molecular approaches to identification of RhD-negative patients waiting for kidney transplantation.

METHODS

A total of 103 RhD-negative blood samples by serological test were collected from patients waiting for kidney transplantation between January, 2006 and January, 2016. Quantitative PCR and sequencing were used to verify the results of RHD genotyping, and the false negative rates of the serological and molecular methods for RhD genotyping were compared.

RESULTS

Among the 103 blood samples, true RhD negativity (with all the 10 exons missing) was found in 56 samples (54.5%), and false RhD negativity (RhD positivity with loss, repetition, or missense mutation in the 10 exons) in 47 samples (45.6%). In the 47 false RhD-negative cases, weak D was detected in 1 case (2.1%), partial D in 13 cases (27.7%), and D-elution in 33 cases (70.2%). The detection rates of RhD negativity differed significantly between the serological and molecular methods (P<0.05).

CONCLUSION

Serological test is associated with a high false negative rate in detecting RhD blood group, and the use of the molecular approach has important clinical significance in accurate RhD genotyping for patients waiting for renal transplantation.

Red Cell Immunohematology Research Conducted in China

ABO subtypes and RhD variants are the most studied blood groups in China. Some of the polymorphisms in these two blood groups have direct clinical relevance. Molecular diagnosis of blood group polymorphisms is underway in China. In addition, research groups have developed methods such as screening for blood group mimetic peptides using phage display technology. New reagents, akin to antibodies directed against RhD and ABO, are being investigated using aptamer-based techniques. Progress is also being made in the development of synthetic exoglycosidases for conversion of group A and/or B antigens to group O. Development of methoxy-polyethylene-glycol modified red cells has been successful in vitro but has not reached clinical application. In this paper, we summarize red cell immunohematology research that has been conducted in China.

An effective diagnostic strategy for accurate detection of RhD variants including Asian DEL type in apparently RhD-negative blood donors in Korea

BACKGROUND AND OBJECTIVES

The purpose of this study was to provide an effective RHD genotyping strategy for the East Asian blood donors.

MATERIAL AND METHODS

RhD phenotyping, weak D testing and RhCE phenotyping were performed on 110 samples from members of the RhD-negative club, private organization composed of RhD-negative blood donors, in the GwangJu-Chonnam region of Korea. The RHD promoter, intron 4, and exons 7 and 10 were analysed by real-time PCR. Two nucleotide changes (c.1227 G>A, and c.1222 T>C) in exon 9 were analysed by sequencing.

RESULTS

Of 110 RhD-negative club members, 79 (71·8%) showed complete deletion of the RHD gene, 10 (9·1%) showed results consistent with RHD-CE-D hybrid, and 21 (19·1%) showed amplification of RHD promoter, intron 4, and exons 7 and 10. Of the latter group, 16 (14·5%) were in the DEL blood group including c.1227 G>A (N = 14) and c.1222 T>C (N = 2), 2 (1·8%) were weak D, 1(0·9%) was partial D, and 2 (1·8%) were undetermined. The RhD-negative phenotype samples consisted of 58 C-E-c+e+, 19 C-E+c+e+, 3 C-E+c+e-, 21 C+E-c+e-, 6 C+E-c+e+ and 3 C+E-c-e + . Notably, all 58 samples with the C-E-c+e+ phenotype were revealed to have complete deletion of the RHD gene. The C-E-c+e+ phenotype showed 100% positive predictive value for detecting D-negative cases.

CONCLUSIONS

RHD genotyping is not required in half of D-negative cases. We suggest here an effective RHD genotyping strategy for accurate detection of RhD variants in apparently RhD-negative blood donors in East Asia.