Partial D phenotypes and genotypes in the Chinese population

Alloanti-D induction in a rare RhD variant (DBT-2) case: Insights from serological and molecular biological testing

BACKGROUND

The RhD antigen is the most immunogenic within the Rh blood group system， playing a pivotal role in clinic. The D variant phenotype is a rare occurrence, characterized by low expression of the D antigen or partial deletion of the RhD antigen on the surface of red blood cells (RBCs). For individuals with the D variant, transfusion with RhD-negative blood is crucial for ensuring transfusion safety.

CASE PRESENTATION

We present a case of a 63-year-old Han Chinese female, identified as a D variant phenotype without a history of blood transfusion but with a history of pregnancy. Pre-transfusion testing revealed the presence of alloanti-D antibodies. Genetic analysis confirmed the patient's genotype as RHD-CE (5-9)-D, and her phenotype was classified as DBT-2.

CONCLUSION

This report marks the first case in China of anti-D alloimmunization in patients with the D variant. Both serological and molecular detection of the D variant are essential to ensure the safety of blood transfusions.

Noninvasive screening of fetal RHD genotype in Chinese pregnant women with serologic RhD-negative phenotype

BACKGROUND

Noninvasive fetal RHD genotyping has been provided to nonimmunized RhD-negative pregnant women to guide anti-D prophylaxis. Among the Chinese, more than 30% of the RhD-negative phenotype is associated with variant RHD alleles, which would limit the accuracy of fetal RHD status prediction; thus, more targeting and proper programs need to be developed.

STUDY DESIGN AND METHODS

Fluorescence quantitative polymerase chain reaction PCR (qPCR) or Sanger sequencing on all RHD exons was used to detect maternal RHD genotypes. For pregnant women with RHD*01N.01 or RHD*01N.03 alleles, the presence of RHD exons 5 and 10 in cell-free DNA was determined by qPCR. For pregnant women with the RHD(1227G>A) allele, high-throughput sequencing on exon 9 of the RHD gene and RHCE gene was used to predict fetal RhD phenotype.

RESULTS

Among 65 cases of Chinese pregnant women with the serologic RhD-negative phenotype, three major genotypes were identified: RHD*01N.01/RHD*01N.01 (61.5%), RHD*01N.01/RHD(1227G>A) or RHD*01N.03/RHD(1227G>A) (20%), and RHD*01N.01/RHD*01N.03 (13.8%), along with three cases of minor genotypes (4.6%). For 43 pregnant women with the RHD*01N.01 or RHD*01N.03 alleles, qPCR on maternal cell-free DNA yielded a 98.5% (42/43) accuracy rate and 100% successful prediction rate. High-throughput sequencing was successfully used to predict fetal RhD phenotypes for 13 pregnant women with RHD(1227G>A).

CONCLUSION

On the basis of maternal RHD genotyping, fetal genotyping through qPCR or high-throughput sequencing can improve the accuracy and success rate of prenatal fetal RhD phenotype prediction among Chinese pregnant women. It plays a potential role in guiding anti-D prophylaxis and pregnancy management in Chinese pregnant women.

Molecular and serological analysis of the D variant in the Chinese population and identification of seven novel RHD alleles

BACKGROUND

The molecular basis of the D variant phenotype in the Chinese differs greatly from that of the Caucasian. Adapting a specific D typing strategy to the spectrum of prevalent RHD variant alleles is necessary.

STUDY DESIGN AND METHODS

Blood samples with ambiguous D phenotypes were collected in the Southern Chinese population. A special three-step typing strategy was applied. First, the common DVI type 3 was identified from epitope profiles of D antigen. Then, another common weak D type 15 (RHD*845A) was identified by epitope profiles of D antigen and Sanger sequencing of RHD exon 6. Finally, the remaining D variants were genotyped mainly by Sanger sequencing. For the novel RHD alleles in the coding region and exon-intron junction, in vitro transfection and minigene splicing assays were performed, respectively. The anti-D investigation was performed.

RESULTS

DVI type 3 (65/253, 25.7%) and weak D type 15 (62/253, 24.5%) were common Chinese D variants, and RHD*960A, DFR, RHD*weak D type 25, 72, and 136 were frequent variant RHD alleles. Besides, twenty-two sporadic and seven novel RHD alleles (RHD*188A; RHD*688C; RHD*782 T; RHD*1181C; RHD*165 T, 993A; RHD*148 + 3G > T and RHD*1227 + 5G > C) were identified. The deleterious effect of the novel RHD alleles on D antigen or mRNA expression was confirmed. Anti-D was detected in two DVI type 3 pregnant women.

DISCUSSION

The three-step typing strategy provides an effective approach for Chinese D variant typing. It can be anticipated that commercially available RHD genotyping kits have limitations for testing Chinese D variants, as some of the frequent variants are not interrogated.

Transfusion management of Africans with RHD variants in China

The presence of D variant among minorities could produce a higher rate of alloimmunization observed in patients from this group. This is partly due to the ethnic and racial specificity of RHD variants and the limited availability of Rh-matched blood donors. Approximately half a million African migrants in China carrying distinct Rh blood type composition have presented to the health care system with an imperative safety requirement of blood transfusion among 1.3 billion Chinese individuals. We depict the clinically significant RHD alleles among African migrants living in China and identify the genetic similarities and disparities to Chinese. We discussed practical strategies to manage the unique transfusion needs of African migrants in China.

Updated Evaluation of RhD Status Among Women of Child-Bearing Age in Detroit, Michigan

OBJECTIVES

The Rh blood group system is one of the most important and immunogenic blood group systems after the ABO blood group system and, like other blood group antigens, it follows ethnic and racial trends. However, when it comes to D variants-partial D and weak D-most of the cohorts studied in the literature have been of European descent. This study aimed to discover the variant D trends in Detroit, Michigan, with an emphasis on Black communities.

METHODS

From 2016 to 2018, there were 102 patients (women of childbearing potential: < 50 years) at Henry Ford Hospital that had serologic D discrepant testing. These patients were sent out for molecular RHD determination.

RESULTS

In total, 12.7% of patients were characterized as RhD positive and 87.3% of patients were characterized as RhD variants (nominated as RhD negative at our institution).

CONCLUSIONS

Our predominantly Black cohort sheds light on the diversity of the RhD antigen. The majority of Blacks were classified as RhD variants (RhD negative nomination at our institution). Therefore, molecular testing for this patient population with serologic RhD discrepancies is paramount to properly manage their obstetric care.

Frequency of RHD variants in serologically weak D Turkish blood donors

BACKGROUND

RhD typing has remained of primary importance, as being the leading cause of hemolytic disease of the newborn. Among Rh system's 55 blood group antigens, RhD is the most immunogenic. We aimed with this study to determine weak D/partial D variant frequency in blood donors who were admitted to our blood center and have serologically designated blood group weak D.

MATERIALS AND METHODS

We screened blood donors who admitted between 2011 and 2017 to our blood center. Sixty-seven serologically weak D phenotyped donors have participated in the study. These donors' samples were studied further by Polymerase Chain Reaction Sequence- Specific Primers (PCR-SSP) for determining D variants.

RESULTS

Weak D phenotype was detected in 228(0.12 %) out of 177,554 donors. Sixty-seven of them agreed to take part in the study. The frequency of weak D and partial D was 68.7 % (n = 46), and 22.4 % (n = 15), in order. The most encountered weak D and partial D variant was type 15 and DFR type, respectively.

CONCLUSIONS

The prevalence of serologically weak D phenotypes varies by race and ethnicity. Turkey is a country covering a mixture of European and Asian DNA with different ethnic groups. Thus, our research as giving the overall distribution of RHD variants from the largest city of Turkey, which may reflect the general ethnic background of the country, would help to the establishment of a databank for blood banking. This paper is the first molecular study on RHD variants in Turkey. New molecular research would be more reliable and precise.

Molecular and computational analysis of 45 samples with a serologic weak D phenotype detected among 132,479 blood donors in northeast China

Background

RH1 is one of the most clinically important blood group antigens in the field of transfusion and in the prevention of fetal incompatibility. The molecular analysis and characterization of serologic weak D phenotypes is essential to ensuring transfusion safety.

Methods

Blood samples from a northeastern Chinese population were randomly screened for a serologic weak D phenotype. The nucleotide sequences of all 10 exons, adjacent flanking intronic regions, and partial 5′ and 3′ untranslated regions (UTRs) were detected for RHD genes. Predicted deleterious structural changes in missense mutations of serologicl weak D phenotypes were analyzed using SIFT, PROVEAN and PolyPhen2 software. The protein structure of serologic weak D phenotypes was predicted using Swiss-PdbViewer 4.0.1.

Results

A serologic weak D phenotype was found in 45 individuals (0.03%) among 132,479 blood donors. Seventeen distinct RHD mutation alleles were detected, with 11 weak D, four partial D and two DEL alleles. Further analyses resulted in the identification of two novel alleles (RHD weak D 1102A and 399C). The prediction of a three-dimensional structure showed that the protein conformation was disrupted in 16 serologic weak D phenotypes.

Conclusions

Two novel and 15 rare RHD alleles were identified. Weak D type 15, DVI Type 3, and RHD1227A were the most prevalent D variant alleles in a northeastern Chinese population. Although the frequencies of the D variant alleles presented herein were low, their phenotypic and genotypic descriptions add to the repertoire of reported RHD alleles. Bioinformatics analysis on RhD protein can give us more interpretation of missense variants of RHD gene.

Serologic findings of RhD alleles in Egyptians and their clinical implications

INTRODUCTION

Serologic discrepancies caused by various reactivity of D variants can only be resolved by the use of RhD genotyping. However, this strategy cannot be applied routinely due to the cost and feasibility. It has been documented that D variants are demonstrated among individuals with positivity for at least C or E antigens. It is considered to be affordable for some countries to test D negative donors who are C or E positive for D variants. It was proposed that an algorithm could be found based on distinct serologic features that matches the Egyptian genetic frequency data, and correctly assigns donors and patients, using the least possible expenses.

MATERIALS AND METHODS

Samples with the most prevalent weak D and partial D were investigated for their RhCE phenotype. Routine D typing by immediate spin (IS) tube method was performed in parallel with an automated gel test, and the reactivity results of D variants with both techniques were compared.

RESULTS

Among 31 D variants, only 5 were C or E positive (16.1 %). R0r phenotype was associated with the remaining 26 samples (83.9%) and constituted weak D types 4.2 (38.5%), and 4.0/4.1 (11.5%), partial DIII (34.6%), and partial DV (15.4%). Gel reacted strongly with partial DIII and DV. Ten samples with DIII and DV typed as D positive with IS. All weak D were positive by indirect antiglobulin test (IAT), while all partial D were positive by gel and IAT.

CONCLUSION

Guidelines for RhD workup should be adjusted to match population data. Detection of D variants among C or E positive donors may not be an optimal strategy for Egyptians. Serology cannot discriminate weak D from partial D, but may provide a clue about the probable D variant to be tested molecularly with the appropriate kit. Reagent selection is important to correctly assign donors and patients with the DIII and DV types.

Policies and procedures related to testing for weak D phenotypes and administration of Rh immune globulin: results and recommendations related to supplemental questions in the Comprehensive Transfusion Medicine survey of the College of American Pathologists

CONTEXT

Advances in RHD genotyping offer an opportunity to update policies and practices for testing weak D phenotypes and administration of Rh immune globulin to postpartum women.

OBJECTIVES

To repeat questions from a 1999 College of American Pathologists proficiency test survey, to evaluate current practices for testing for weak D and administration of Rh immune globulin, and to determine whether there is an opportunity to begin integrating RHD genotyping in laboratory practice.

DESIGN

The College of American Pathologists Transfusion Medicine Resource Committee sent questions from the 1999 survey to laboratories that participated in the 2012 proficiency test survey. The results of the 2012 survey were compared with those from 1999. Results from published RHD genotyping studies were analyzed to determine if RHD genotyping could improve current policies and practices for serological Rh typing.

RESULTS

More than 3100 survey participants responded to the 2012 questions. The most significant finding was a decrease in the number of transfusion services performing a serological weak D test on patients as a strategy to manage those with a weak D as Rh negative (from 58.2% to 19.8%, P < .001). Data from RHD genotyping studies indicate that approximately 95% of women with a serological weak D could be managed safely and more logically as Rh positive.

CONCLUSIONS

Selective integration of RHD genotyping policies and practices could improve the accuracy of Rh typing results, reduce unnecessary administration of Rh immune globulin in women with a weak D, and decrease transfusion of Rh-negative red blood cells in most recipients with a serological weak D phenotype.

Evaluation of a blood group genotyping platform (BLOODchip(®) Reference) in Japanese samples

BACKGROUND

Blood-group genotyping arrays have been widely used in Caucasian and African American populations, but have not been thoroughly tested in Japanese subjects.

AIM

To evaluate, using the BLOODchip(®) Reference genotyping system, the concordance of previously typed samples with expected phenotypes and the coverage of the Japanese variants.

METHODS

Blood samples from 100 Japanese donors were obtained. DNA was extracted with QIAsymphony (Qiagen, Hilden, Germany). Samples were typed by serological methods and processed with the BLOODchip(®) . When a non-concordant result was identified, further sequencing by polymerase chain reaction-single specific primer (PCR-SSP) was performed.

RESULTS

Concordance between systems was 98% (736/751), and 98.8% (742/751) if only non-software-related non-concordances were considered. In the ABO group, 6 'No Call' (NC, inability of the BLOODchip(®) to assign a result) were ascribed to a variant of blood subtype A1 (A102; 467C>T), a common subtype in Asian populations, whereas three NC presented additional polymorphisms not contained in the BLOODchip(®) (A102/A205, A102/O06 and A204/O02). In the RhD group, one discrepancy was correctly genotyped as RHD*1227A (Del phenotype) by the BLOODchip(®) (phenotyped as partial D, RHD*DIVb). Another was phenotyped as D+ by the BLOODchip(®) (phenotyped weak D by serology) and confirmed as RHD*D-CE(2)-D heterozygous by sequencing. The 3 RhD NC can be solved by further software update. For RhCE, one discrepancy was correctly genotyped for both systems; however, only the BLOODchip(®) was able to detect RHCE*CX allele.

CONCLUSIONS

By programming the A102 ABO variant into the system software with the new allele combinations, the BLOODchip(®) Reference is a suitable genotyping tool to be applied to Asian samples.