Difficulties in Immunohaematology : The Weak D Antigen

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.

Serological and molecular characterisation of the most prevalent weak D variants in Croatian population

INTRODUCTION

Existence of hundreds of RHD gene variants contributes to variable D antigen expression and inconsistencies in reporting the RHD results. The aim of the study was to determine the serological and molecular characteristics of the most prevalent RHD alleles encoding serologically weak D variants.

MATERIAL AND METHODS

Blood donors (n = 145 924) were typed for D antigen using the direct serologic micromethod. Nonreactive samples were analysed in IAT method with the IgM/IgG anti-D monoclonal blend, and 0,2% (n = 263) confirmed weak D antigen expression. After genomic DNA extraction (Qiaqen, Germany), RHD genotyping was performed using in house reagents and PCR-SSP kits (Inno-Train, Germany).

RESULTS

The prevalence of serologically weak D in blood donor population was 0.2% (n = 263). RHD genotyping confirmed weak D allele in 92.4% and partial D allele in 7.6%. The most common was weak D type 1 (49.7%) followed by weak D type 3 (24.7%) and type 2 (9.5%). Relatively high frequency was detected for weak D type 14 (4.6%) and type 64 (2.3%). In the category of partial D phenotypes, only DVI variant was found. Direct typing has shown great variability in the strength of reactions with different clones of anti-D reagents.

CONCLUSION

Weak D type 1 is the most common weak D variant in Croatian blood donor population. The frequency of D variants and distribution of Rh phenotypes in our study was in concordance with other studies. It has been shown that serological methods and the combination of clones used, cannot distinguish variant D types, which justifies the use of molecular methods.

Variable reactivity of Rh D antigen and its serological characterization

Background: Variation in the reactivity on Rh D typing may pose challenges in interpretation and ambiguity in further patient management.Materials and Methods: A prospective study was conducted in the department of transfusion medicine for a period of 18 months. Blood grouping was performed by fully automated equipment employing column agglutination technique. All the samples with Rh D negative or discrepant reactions were subjected to weak D testing by the antihuman globulin testing method. Samples that tested positive were categorized as serological weak D type or Variant D and were further phenotyped with Partial D typing set with 6 monoclonal anti D antisera.Results: A total of 82,824 samples were tested for Rh D type during the study period. Of the study population, 65.7% were males. On Rh D type majority were Rh D positive (93%), 6.9% were negative, and the result was discrepant in 0.1% (70) samples. The overall prevalence of variant D was 1.28% (75) of the Rh D negative population and 0.09% of the total study population. The detection rate of variant D phenotype was significantly higher by the Column agglutination technique. Upon testing with Partial D kit, the partial D variant in the majority reacted wil all the 6 antisera and hence we could not rule out DIII(60%), in rest it was inconclusive. In 43% of subjects with Rh D discrepancy 'C' antigen was found in a homozygous state.Conclusion: The introduction of partial D typing kit alone may not help in the absolute characterization of variant D. Extended serological testing and selective integration of molecular testing is the need of the hour.

ABO, Rh, and kell blood group antigen frequencies in blood donors at the tertiary care hospital of Northwestern India

BACKGROUND:

This study was performed to provide information on frequencies of ABO, Rh & Kell antigens/alleles, phenotype in blood donors at Blood Bank, SMS hospital, Jaipur and to compare them with other races.

METHODOLOGY:

This study was conducted on blood donors from April 2016 to March 2017 using a fully automated system for ABO,Rh & Kell typing of blood cells. D, C, c, E, e & K antigens were typed using monoclonal antisera from Immucor The data were collected and calculations done to determine the antigen/allele, phenotype. The chi square test 3 degree of freedom with P < 0.001 (S) was used for comparisons between the results of our study and those of other studies.

RESULTS:

A total of 8067 donors were included in this study. Maximum donors was of B blood group (39.4%) of age 18-25(35.5%) with 60-69kg weight (65%). The most common Rh antigen found was e(99.3%) followed by D (93.8%), C (85.4%), c (60.1%), E (17.5%). R1r (DCCee) was the most common phenotype in our study (39.5%). Kell (K+) antigen was present in 2.7% of donors.

CONCLUSION:

We have determined the prevalence of Rh antigens and Rh phenotypes in blood donor at our hospital and derived the allele frequencies in the same population.

Testing for weak D Antigen: Spectrum and its applied role in rhesus-negative transfusions in Andaman and Nicobar Islands

Objectives

Rhesus (Rh) blood group with variable expression of D antigen is one of the complex systems in immunohematology. Weak D antigen is a phenotype where the D antigen is weakly expressed on red blood cells, and this antigen cannot be detected by routine methods. This study was conducted to determine the frequency of Rh D negativity and weak D antigen among healthy blood donors and to review the clinical significance of weak D antigen pertaining to Rh D-negative transfusions.

Materials and Methods

This cross-sectional prospective study was conducted in G. B Pant Hospital from January 2016 to June 2017 in which all the blood donors from Port Blair and adjacent islands of Andaman and Nicobar were grouped for Rh D antigen and those who tested negative for the D antigen were further tested for weak D antigen by incubating for 30 min and subsequent addition of anti-human globulin sera.

Results

Out of 6415 donors, 6085 (94.86%) were Rh D positive and 330 (05.14%) were Rh D negative. Among the Rh D-negative donors, 05 (01.51%) were positive for weak D antigen. The frequency of Rh D negativity was 25.76% in a blood group, 25.15% in B, 07.88% in AB and 41.21% in O blood group phenotype.

Conclusion

Although the frequency of weak D antigen is low (01.51%), the strong immunogenicity of Rh D antigen discernates the need for appropriate testing for weak D antigen. This is of particular concern in Rh D-negative pregnant females as it can produce alloimmunization if accidentally given weak D antigen positive blood.

RHD-Positive Alleles among D- C/E+ Individuals from India

Background

Molecular bases of blood group systems, including Rh blood group, have been poorly studied in the Indian population so far, while specificities of Europeans, East Asians and Africans have been well known for years. In order to gain insights into the molecular bases of this population, we sought to characterize the RHD allele in D- Indian donors expressing C and/or E antigen(s).

Methods

RHD gene was analyzed in 171 serologically D-, C/E+ samples by standard molecular methods such as quantitative, multiplex PCR of short fluorescent fragments (QMPSF) and direct sequencing when necessary.

Results

RHD whole gene deletion at the homozygous state was found to be the most common genotype associated with D- phenotype (118/171, 69.0%). Nonfunctional, negative hybrid genes with reported molecular backgrounds were observed in approximately one-third of the samples, while only four samples carry single-nucleotide variations, including one novel nonsense (RHD(Y243X)), one novel frameshift (RHD(c.701delG)), and two missense (RHD(T148R) and RHD(T148R, T195M)) alleles.

Conclusion

Overall we report for the first time the molecular bases of D antigen negativity in the D-, C/E+ Indian population, which appears to be qualitatively similar to other populations, but with a population-specific, quantitative distribution of D-- alleles.

Enigmatic Weak D antigen: An Experience in a Tertiary Care Hospital of East Delhi

INTRODUCTION

The Rh blood group system is one of the most polymorphic and immunogenic blood group systems in humans. The expression of Rh blood group antigen is complex, among that Rh-D antigen is the most important antigen because of its immunogenicity. It is easy to detect D antigen in most of the cases. Sometimes, variable expression of Rh-D antigen leads to presence of weak forms. Weak D reacts variably with anti D sera and poses a problem in blood banking. Molecular genetics of Rh-D revealed that weak D antigen is a Rh-D phenotype that possesses less numbers of complete D antigens on the surface of red blood cells.

AIM

Present study was carried out to study weak D positivity in a tertiary neuropsychiatry hospital of East Delhi for compatibility testing in blood transfusion, to assess the implications and need of weak D testing and for population genetics study. This study tried to observe pattern of weak D antigen in four broadly classified religious communities also (Hindus, Muslims, Sikhs and Christians).

MATERIALS AND METHODS

This was a two years prospective hospital based study including patients as well as donors. All patients were tested for Rh-D factor by commercially available monoclonal anti-D sera. The individuals who were found negative with anti-D were further investigated for weak D antigen by using indirect antiglobulin test (IAT) by tube as well as gel card technique.

RESULTS

The results were compiled by using SPSS software version 21.0 and Microsoft excel. Among 3619 cases, 3502 (96.7%) were Rh-D factor positive while 117(3.2%) were Rh D factor negative. Among these 117 Rh-D negative cases, 9 (7.6% out of total Rh-D negatives and 0.25% out of total samples) were weak D positive and 108(2.98%) were actually D negative individuals after IAT. Weak D positivity showed a slight predominance in females (55.5%). As per broad religious communities, weak D antigen was found in Hindus only and not observed in Muslims, Sikhs and Christians. In weak D positive individuals, B phenotype (0.43%) was found to be most common followed by A (0.26%) and O (0.2%).

CONCLUSION

Considerably high frequency of weak D antigen was noticed in study samples of this hospital. With this data based information, it is felt worthwhile to perform weak D testing routinely of those individuals who are negative with saline anti-D to prevent possibility of haemolysis and for efficient blood transfusion practices by making compatible blood available.

Proportion of Rh phenotypes in voluntary blood donors

BACKGROUND

The Rh system is the major blood group system besides ABO system. Even after proper blood grouping and cross matching there is a possibility of alloimmunization and antibody production in the recipients against the Rh or minor blood group antigens like Kell, MNSs, Duffy etc. Keeping in view the heavy financial burden of complete phenotyping of blood; the determination of only Rh phenotypes can play a major role in preventing alloimmunization and adverse events in multitransfusion cases. To determine the proportion of Rh phenotypes in voluntary blood donors with a view to generate blood bank data for constitution of panel of blood donors for multipurpose utilities.

METHOD

Identification of Rhesus factors (Rh) was done by the antigen antibody agglutination test by the test tube method on 10,133 healthy voluntary donors.

RESULTS

The phenotypic frequencies of Rh blood groups in the studied population were D-92.25%, C-87.55%, E-26.55%, c-51.06% and e-98.42%. Thus 'e' was the most common and E was the least common of all the Rh types. Phenotypically DCCee group was the most common phenotype and dccee was least common type.

CONCLUSION

Determination of Rh phenotypes can play a major role in preventing alloimmunization and avoiding adverse events in multitransfusion cases.