Variant RHD Types in Brazilians With Discrepancies in RhD Typing

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.

Standardization of a multiplex assay to identify weak D types in a mixed-race Brazilian population

RH allele variability is caused by several types of variants, resulting in altered RhD and RhCE phenotypes. Most of the weak D phenotypes in European-derived populations are weak D types 1, 2, or 3, which are not involved in alloimmunization episodes. However, the Brazilian population is racially diverse, and the accuracy of molecular and serologic tests developed in recent years has allowed for the identification of other RH variants, that are common in the Brazilian population, such as weak D type 38 or weak partial 11, the latter involved in alloimmunization cases. Furthermore, patients with these two weak D variants must be transfused with D- red blood cell units, as do patients with weak D type 4 or DAR, which are also common D variants in Brazil. Weak D type 38 and weak partial 11 can be serologically misclassified as weak D types 1, 2, or 3 in patients, based on European experience, or as D- in donors. Additionally, pregnant women may unnecessarily be identified as requiring Rh immune globulin. RhCE phenotypes are reliable indicators of RhD variants. For individuals with the Dce phenotype, the preferred approach is to specifically search for RHD*DAR. However, when encountering DCe or DcE phenotypes, we currently lack a developed method that assists us in rapidly identifying and determining the appropriate course of action for the patient or pregnant woman. Two multiplex assays were proposed: one for the identification of RHD*weak partial 11, RHD*weak D type 38, and RHD*weak D type 3 and another for RHD*weak D type 2 and RHD*weak D type 5. The multiplex assays were considered valid if the obtained results were equivalent to those obtained from sequencing. Expected results were obtained for all tested samples. The proposed multiplex allele-specific polymerase chain reaction assays can be used in the molecular investigation of women of childbearing age, patients, and blood donors presenting a weak D phenotype with DCe or DcE haplotypes in a mixed-race population, such as Brazil.

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 and characterization of RHD variant alleles in a population of blood donors from southeastern Brazil: Comparison with other populations

BACKGROUND

The correct determination of D antigen could help to avoid alloimmunization in pregnant women and patients receiving blood transfusions. However, there are limitations in the identification of D variants as the partial and weak D phenotypes make the determination of D antigen a great challenge in the transfusion routine.'

STUDY DESIGN AND METHODS

The molecular characterization of D variants was performed on blood donors from southeastern Brazil with atypical D typing. Furthermore, the serological profile of all RHD variant alleles identified was analyzed using different Anti-D clones. The prevalence of RHD alleles and genotypes found was compared with those described in other countries and in other regions from Brazil.

RESULTS

Atypical serologic D typing occurred in 0.79 % of blood donors. The majority of RHD variant alleles (88 %) were first characterized by multiplex PCR and PCR-SSP as RHD*weak partial 4 (47 %), followed by RHD*weak D type 3 (29.9 %), RHD*weak D type 2 (3.9 %) and RHD*weak D type 1 (3.1 %). Genomic DNA sequencing characterized the RHD*weak partial 4 variants found in RHD*DAR1.2 (weak 4.2.2) (22 %), RHD*DAR3 (weak 4.0.1) (2.4 %), RHD*DAR3.1 (weak 4.0) (22 %) and RHD*DAR4 (weak 4.1) (0.8 %). RHD variant alleles associated with partial D, such as, RHD*DAU-4 (1.6 %), RHD*DAU-5 (2.4 %), RHD*DAU-6 (1.6 %), RHD* DIII type 8 (1.6 %), RHD*DVII (3.9 %) and RHD* DMH (0.8 %) were also observed.

CONCLUSION

The prevalence of RHD variant alleles observed in this cohort differ from those found in other populations, including Brazilians from other regions. RHD allele distribution in specific regions should be considered for implementation of algorithms and genotyping strategies aiming at a more effective and safe transfusion.

Variant genotypes associated with reduced expression of RhCE antigens among Brazilian blood donors

BACKGROUND

The genetic diversity of the RHCE gene locus has been explored in diverse populations of different racial backgrounds. Data referring to the diversity of RHCE encoding weakened expression of C, c, E, and e in multiethnic populations is still incomplete.

METHODS

Samples from Brazilian blood donors presenting reduced expression of C, c, E, or e on gel method were selected for the study. All exons and flanking introns of RHCE were genotyped though direct Sanger sequencing for the included donors.

RESULTS

Sixty-six donors were included: 23 with weak C, 22 with weak c, 6 with weak E, 14 with weak e, and 1 with weak c and E. Among the samples with weak C, the following altered RH*C were encountered: RHCE*CeMA (n = 3), RHCE*Ce941C (n = 1), and RHCE*CeVA (n = 1). RHD*D-CE(4-7)-D was detected in six cases, RHCE*CE was presumably present in five cases, and seven cases were unexplained. Two altered alleles underlay the weak c phenotype: RHCE*ceJAL (n = 20) and RHCE*ce340T (n = 2), and two altered RHCE justified weak e: RHCE*ceMO (n = 6) and RHCE*ceJAL (n = 8). Three variant RHCE were associated with weak E: RHCE*cEJU (n = 4), RHCE*cE382C (n = 1), and RHCE*cEIV (n = 1). The RHCE*cE905A justified one case of weak c and E.

CONCLUSION

We describe the distribution of RHCE variants found in association with weak expression of C, c, E, and e in blood donors of multiethnic origin, which differs in comparison to that previously reported for people of African or Caucasian descent.

RHD and RHCE molecular analysis in weak D blood donors and in patients with Rh antibodies against their own corresponding Rh antigen

BACKGROUND

The Rh system is the largest and most polymorphic blood group system. The existence of a large number of RH alleles results in variant phenotypes that often complicate blood donor phenotyping and the distinction between auto- and allo-antibodies in recipients who have anti-Rh antibodies in the presence of their own corresponding Rh antigen. Knowledge of these variants is necessary in order to make blood transfusion safer.

MATERIALS AND METHODS

Samples from 48 blood donors with serological weak D and from 29 patients who had anti-Rh antibody in the presence of their own corresponding Rh antigen were evaluated molecularly for RHD and RHCE alleles using a blood-multiplex ligation-dependent probe amplification assay and Sanger sequencing.

RESULTS

Rh variants were found in 45 of the 48 blood donors: 24/45 (53%) were weak D, 2/45 (4%) partial D and 19/45 (42%) were weak and partial D. The remaining three donors (6%) did not show a mutation in the RHD allele. Among the 29 patients, 13/29 had anti-e, of whom 4/13 had genotypes that predicted a partial e antigen; 11/29 had anti-D, with 6/11 being identified as partial D; 2/29 had anti-c, of whom 1/2 was predicted to express partial c antigen; 4/29 who had anti-E and 4/29 who had anti-C did not show mutations in RHCE*C or RHCE*E.

DISCUSSION

It was possible to find individuals with clinically significant Rh phenotypes due to the weak reactivity of the D antigen, detected through serological tests in blood donors. In patients, when found with the anti-Rh antibody in the presence of the same Rh antigen, it is difficult to distinguish an auto-antibody from an allo-antibody by serological tests; in these cases, molecular methods (genotyping) can help us to determine whether there are changes in the RH alleles and to discover the nature of the antibody (allo or auto).

Serologic strategy in detecting RHD altered alleles in Brazilian blood donors

Background

We evaluated different technological approaches and anti-D clones to propose the most appropriate serologic strategy in detecting the largest numbers of D variants in blood donors.

Methods

We selected 101 samples from Brazilian blood donors with different expressions of D in our donor routine. The tests were performed in immediate spin (IS) with eleven commercially available anti-D reagents in a tube and microplate. The D confirmatory tests for the presence of weak D included the indirect antiglobulin test (IAT) in a tube, gel and solid-phase red blood cell adherence (SPRCA). All DNA samples were extracted from peripheral blood and the D variants were classified using different molecular assays.

Results

The RHD variants identified by molecular analysis included weak D types (1, 2, 3, 11 and 38) and partial Ds (DAR1.2, DAR1, DAR3.1, DAU0, DAU2, DAU4, DAU5, DAU6, DMH and DVII). The monoclonal-monoclonal blend RUM-1/MS26 was the best anti-D reagent used in detecting the D antigen in the IS phase in a tube, reacting with 83.2% of the D variants, while the anti-D blend D175 + 415 was the best monoclonal antibody (MoAb) used in a microplate to minimize the need for an IAT, reacting with 83.2% of the D variants. The D confirmatory tests using SPRCA showed a reactivity (3 - 4+) with 100% of the D variant samples tested.

Conclusion

Our results show that, even using sensitive methods and MoAbs to ensure the accurate assignment of the D antigen, at least 17% of our donor samples need a confirmatory D test in order to avoid alloimmunization in D-negative patients.

Characterization of RHD locus polymorphism in D negative and D variant donors from Northwestern Argentina

BACKGROUND

A notable RHD variability has been observed in Central Argentina's current population attributed to the intermixing of different ethnic groups. The Northwestern region of the country is characterized by a markedly Amerindian genetic contribution. In this sense, the definition of the RHD polymorphism in individuals from this area was lacking.

STUDY DESIGN AND METHODS

A total of 757 donors from Northwestern Argentina, with D negative C and/or E positive (n = 526), and D variant (n = 231) phenotype defined by standard hemmaglutination tube techniques were genotyped using in-house PCR strategies, commercial SNP arrays and Sanger sequencing.

RESULTS

Among D negative C and/or E positive samples, RHD null (15.40%) and DEL alleles (3.23%) were identified. One unreported SNP c.1001T>A responsible for a null allele was found. RHD*01N.75 (4.18%) and RHD*DEL43 (2.66%) were the most prevalent variants following RHD*03N.01 (8.75%). The characterization of serologic weak D phenotypes showed that RHD*weak D type 1, 2, and 3 variants were found only in 37.24% of the samples, whereas RHD*weak D type 93 was the most prevalent allele (25.11%). Also, a previously unreported missense variation c.764G>A was identified.

CONCLUSIONS

A RHD genotyping strategy for patients and donors from Northwestern Argentina must consider the detection of the frequently found RHD*01N.75, RHD*DEL43, and RHD*weak D type 93 variants. Taking into account that RHD*DEL43 has scarcely been found in North Americans and Europeans whereas RHD*01N.75 and RHD*weak D type 93 have never been described in populations other than Argentineans, these RHD variants could be attributed to Native Amerindian genetic influence.

Frequency and characterization of RHD variants in serologically D- Surinamese pregnant women and D- newborns

BACKGROUND

Numerous RHD variant genes affect the expression of D on the red blood cell surface. In Suriname, 4.3% of pregnant women were D-, ranging from virtually zero to 7% among ethnic groups. Characterization of RHD variants, which are associated with a variable potential to induce anti-D, is of practical clinical importance especially in case of limited access to preventive measures. Here we report on the occurrence of RHD variant genes in Surinamese serologically D- pregnant women and their D- newborns from different ethnic groups.

STUDY DESIGN AND METHODS

The RheSuN study is a cross-sectional cohort study in D- pregnant women and their newborns, who visited hospitals in Paramaribo, Suriname, during routine pregnancy care. The presence of RHD variants was investigated using quantitative polymerase chain reaction targeting RHD Exons 5 and 7 and RH-multiplex ligation-dependent probe amplification.

RESULTS

Seven RHD variant genes were detected in 35 of 84 women and four RHD variant genes in 15 of 36 newborns. The RHD*03 N.01 and RHD*08 N.01 variants represented 87% of a total of 62 variant genes. Variants were comparably frequent among ethnicities. In four cases genotyping would have changed anti-D prophylaxis policy: one woman with a RHD*01EL.01 variant, not associated with anti-D formation and three D- newborns with RHD*09.01 and RHD*09.03.01 variants, potentially capable of inducing anti-D.

CONCLUSION

RHD variants at risk for anti-D are common among serologic D- individuals from African descent in Suriname. While genotyping D- women has limited added value, it may be considered in newborns from D- women.

High frequency of variant RHD genotypes among donors and patients of mixed origin with serologic weak-D phenotype

BACKGROUND

The current transfusion policy recommended for individuals with serologic weak-D phenotype is based on data derived from European-descent populations. Data referring to the distribution of RH alleles underlying weak-D phenotype among people of mixed origin are yet incomplete, and the applicability of European-based transfusion guidelines to this specific population is questionable.

GOAL

To evaluate the distribution of RHD variant genotype among individuals with serologic weak-D phenotype of both African and European descent.

METHODS

Donors and patients of mixed origin and with serologic weak-D phenotype were selected for the study. They were investigated using conventional RHD-PCR assays and RHD whole-coding region direct sequencing.

RESULTS

One hundred and six donors and 58 patients were included. There were 47 donors and 29 patients with partial-D genotype (47/106, 44.3%, and 29/58, 50%, respectively). RHD*DAR and RHD*weak D type 38 represented the most common altered RHD alleles among donors (joint frequency of 39.6%), while weak D types 1-3 accounted for 10.4% of the total D variant samples. RHD*DAR was the most common allele identified in the patient group (frequency of 31%), and weak D types 1-3 represented 29.3% of the total.

CONCLUSION

The frequency of partial D among mixed individuals with serologic weak-D phenotype is high. They should be managed as D-negative patients until molecular tests are complete.