Anti-D (-RH1) of the Rh blood group system is clinically important as it causes haemolytic transfusion reactions and haemolytic disease of the fetus and newborn. Although most people are either D+ or D−, there is a plethora of D variants, often categorized as either weak D or partial D. These two types are inadequately defined and the dichotomy is potentially misleading. DVI is the D variant most commonly associated with anti-D production and UK guidelines recommend that patients are tested with anti-D reagents that do not react with DVI. Weak D types 1, 2, and 3 are seldom, if ever, associated with alloanti-D production, so a policy recommendation would be to treat patients with those D variants as D+, to preserve D− stocks, whereas patients with all other D variants would be treated as D−. All donors with D variant red cells, including DVI, should be treated as D+.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/bjh.12275

Variants of RhD--current testing and clinical consequences.

Background The D antigen is the most immunogenic antigen in the Rh system D variants must be considered if there is a significant discrepancy in the strength of reaction obtained with different anti-D reagents, a discrepancy between current and historical test results and if anti-D is detected in an individual serologically typed as RhD positive A panel of monoclonal anti-D reagents can be used to identify partial D and weak D variants The aim of this study was to develop a strategy for RhD typing in discrepant cases Materials and methods Sixty RhD discrepant samples referred to our Institute for confirmation of RhD status were tested with a panel of 12 monoclonal anti-D reagents (ALBAclone advanced partial RhD typing kit) and Rh phenotype was determined using C, c, D, E, and e antisera Results Ninety-three percent of the RhD discrepant cases were classified into weak and partial D using this kit Among the D variants characterised, 37% belonged to DFR, 23% to DOL, 12% to weak D, and the remaining 21% to DAR, DV, DMH, DCS and DVI categories Ninety-seven percent of the D variants were "C" antigen positive Out of the panel of 12 monoclonal anti-D used, cell line LHM-70/45 gave negative reactions with all RhD discrepant cases and cell lines LHM-76/59, LHM-76/55 and ESD-1 gave positive reactions with all 60 RhD discrepant cases studied Discussion The Advanced partial D kit was very useful in characterising and identifying D variants in the Indian population A preliminary strategy for the detection and identification of D variants in discrepant cases could be to test for the presence of "C" antigen with anti-C, and for "D" antigen with anti-D of cell line LHM 70/45 A more comprehensive, but simple way to identify D variants in routine RhD typing is to use two anti-D reagents ie LHM 70/45 and one out of LHM-76/59, LHM-76/55 and ESD-1 D variants can be further characterised by using the partial D typing kit and molecular genotyping in specialised laboratories

A simple diagnostic strategy for RhD typing in discrepant cases in the Indian population.

Introduction Determination of RhD variants in blood donors, pregnant women, and newborns is important for transfusion strategies, in order to prevent RhD alloimmunisation and hemolytic disease of fetuses and newborns. Implementation of molecular RHD typing in two transfusion institutes is presented in this article, from Banja Luka (Bosnia and Herzegovina) and Belgrade (Serbia). Study design and methods Blood donors' RhD was checked by direct agglutination assays (tube) and indirect antiglobulin test (gel). Molecular RHD typing was performed by PCR-SSP with fluorometric signal detection in both centres. Donors were selected by weak RhD serological reactivity (Banja Luka, 85 samples; Belgrade, 62 samples) or serologically RhD-negative C/E-positive results (Banja Luka, 92 samples; Belgrade, 61 samples). Results Among serologically determined weak D donors from the institute from Banja Luka, weak D type 3 was the most frequent (58.8%), followed by type 1 (35.3%) and DNB (1.2%), whereas results obtained at the Belgrade institute were distributed between weak D type 1 (41.9%), type 3 (30.7%), type 14 (6.5%), type 15 (1.6%), and DNB with anti-D (1.6%). In 17.7% of serologically typed weak D samples from the Belgrade institute, the molecular typing result was standard D. Additionally, RHD presence was detected in 9.8% of serologically RhD-negative, C/E-positive samples from both institutes. Conclusion Rh molecular testing was successfully implemented in both blood transfusion institutes in Banja Luka and Belgrade. This study proved the efficiency of serological algorithms for weak D, as well as the presence of the RHD gene among serologically tested RhD-negative, C/E-positive samples.

/pdf/implementation-of-molecular-rhd-typing-at-two-blood-1jo13rddza.pdf

Implementation of Molecular RHD Typing at Two Blood Transfusion Institutes from Southeastern Europe

https://aob.amegroups.com/article/download/6532/pdf

Molecular genetics of the Rh blood group system: alleles and antibodies—a narrative review

AIM to estimate the spread of weak D antigen types of the Rhesus system in the citizens of the Russian Federation and a possibility of serologically identifying these types. SUBJECTS AND METHODS The red blood cells and DNA of people with weakened expression of D antigen were investigated using erythrocyte agglutination reaction in salt medium (2 methods); agglutination reaction in the gel columns containing IgM + IgG anti-D antibodies, indirect antiglobulin test with IgG anti-D antibodies (2 methods); polymerase chain reaction to establish the type of weak D. RESULTS A rhesus phenotype was determined in 5100 people in 2014-2015. The weakened agglutinable properties of red blood cells were detected in 102 (2%) examinees. 63 examinees underwent genotyping to identify the variants of the weak D antigen, which identified 6 weak D types. There were the most common weak D types 3 (n=31 (49.2%)) and weak D type 1 (n=18 (28.6%)), including weak D type 1.1 in one (1.6%) case. The other 4 weak D antigen types were as follows: weak D type 2 (14.3% (n=9)), weak D type 15 (4.8% (n=3)), weak D type 4.2 (DAR) (1.6% (n=1)) and weak D type 6 (1.6% (n=1)). The antiglobulin test in the gel column containing antiglobulin serum was the most sensitive serological assay to identify the weak D antigen. Only a molecular test could establish weak D type 15 in 2 samples of red blood cells with Ccdee and ccdEe phenotypes. CONCLUSION The weak D antigen could be serologically identified in 96.8% of cases. When testing for weak D, particular attention should be given to people with the D-negative phenotype who had the C or E antigens. Our investigations conducted for the first time in Russia will be able to improve the immunological safety of red blood cell-containing medium transfusions for patients.

Molecular serological characteristics of weak D antigen types of the Rhesus system

Patient samples were referred to our immunohematology reference laboratory to investigate the presence of a weak D antigen. In the last 3 years, 26 samples were received. Serology and molecular analyses were performed to identify the weak D variant. RHD mRNA from all patients was reverse transcribed, and cDNA was sequenced. The results were compared with a normal RHD sequence to identify the polymorphisms causing the weak D phenotype. Five different already known RHD variants were observed: weak D type 1 (5 individuals), weak D type 2 (1 individual), weak D type 42 (17 individuals), weak D type 45 (1 individual), and partial D DNB (2 individuals). Surprisingly, weak D type 42 was prevalent in our population, whereas weak D type 1, 2, and 3 are the most prevalent variants elsewhere. Anti-D was found in six cases of weak D type 42. The higher prevalence of weak D type 42 could be the result of a founder effect. Additional studies are needed to estimate the frequency of this variant in the general population.

/pdf/weak-d-type-42-cases-found-in-individuals-of-european-3eobz83eh9.pdf

Weak D type 42 cases found in individuals of European descent.

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Weak D type 42 cases found in individuals of European descent.