Frequency of partial D in Western India

Weak D testing might be discontinued for RhD-negative blood donors with C and E negative phenotypes in the Indian population

BACKGROUND

Although serological testing to determine weak D status using the antihuman globulin reagent has been phased out for RhD-negative donors in many countries after the availability of RHD genotyping, it is routinely performed in India. However, weak D testing is a resource-intensive and time-consuming process. We devised a new algorithm for weak D testing in RhD-negative blood donors by performing CcEe phenotyping followed by weak D testing in only C+ and/or E + samples and compared it with the existing protocol in terms of time and cost-effectiveness.

METHOD

In this observational study, we tested 500 samples of RhD-negative blood donors over one year in India. The existing and new algorithms were compared, and the agreement was calculated in terms of the test results, time required for testing, and total cost involved. The RhD type, weak D status, and CcEe phenotypes were determined using the conventional tube technique. An adsorption-elution test was performed to check for the Del phenotype. We conducted RHD genotyping for all samples negative for weak D testing.

RESULTS

The proposed algorithm showed perfect agreement with the existing protocol (agreement = 100 %; κ= 1.00). By applying the new algorithm, we could reduce 71.63 % of testing time and 24 % of total cost without missing any weak D positive samples in blood donors.

CONCLUSIONS

Weak D testing might be discontinued for RhD-negative blood donors with C and E negative phenotypes in the Indian population and could be restricted to only C+ and/or E + phenotypes, which seems to be a time- and cost-effective testing strategy.

RHD Genotyping of Rh-Negative and Weak D Phenotype among Blood Donors in Southeast Iran

Background: The D antigen is a subset of Rh blood group antigens involved in the hemolytic disease of the newborn [HDFN] and hemolytic transfusion reaction [HTR]. The hybrid Rhesus box that was created after RH gene deletion, was known as a mechanism of the Rh-negative phenotype. Hybrid marker identification is used to confirm the deletion of the RHD gene and to determine zygosity. This study aims to detect this marker in Rh-negative and weak D phenotype blood donors of the southeast of Iran.

Materials and Methods: The molecular analysis of the hybrid Rhesus box was performed on the 200 Rh-negative blood donors in Sistan and Baluchestan province, southeast Iran. The presence of alleles responsible for the D variants was assessed by DNA sequencing in 26 weak D phenotype donors.

Results: Of the 200 Rh-negative blood samples, 198 samples were homozygous (99%), and two samples were heterozygous (1%). Heterozygous samples had RHD*01N.73 allele and the RHD*01N.18 allele. Of the 26 samples with weak D phenotype, 16 partial DLO (61%), 4 partial DBT1 (15.3%), 2 partial DV type 2 (7.7%), 1 weak D type 1, 1 weak D type 4.2.3, 1weak D type 105 and 1 RHD (S103P) (4%) were determined.

Conclusion: Since RHD gene deletion is the main mechanism of the Rh-negativity in Sistan and Baluchestan provinces, a hybrid Rhesus box marker can be used in resolving RhD typing discrepancies by RHD genotyping 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.

Molecular characterization of RhD variant phenotypes among blood donors: A study from the coastal region of India

BACKGROUND

RhD expression varies with population and ethnicity. Accurate typing of RhD antigen among blood donors is important to prevent development of anti-D among recipients of blood transfusion. We aimed to screen blood donors for variant D phenotypes and accurately characterize them by genotyping.

MATERIAL AND METHODS

We have done prospective study on blood donors by performing RhD typing using three different commercial monoclonal anti-D reagents by both column agglutination and conventional tube techniques. Samples that showed ambiguous results were further screened with the Bio-Rad Partial RhD typing kit. Minor phenotyping for C, c, E, e antigens was performed. Multiplex PCR and Sequencing of all RHD exons with Sanger's sequencing was performed for molecular characterization of variant D.

RESULTS

A total of 16,974 blood donors were screened during the study period. Among them, 31 (0.18 %) donors were found to have a RhD variant phenotype. The male to female ratio was 10:1. The presence of 'C' antigen was noted among all RhD variant samples. Serological typing identified two samples as DV phenotype and the rest could not be characterized. Molecular genotyping characterized 90.3 % of the samples as Indian specific weak D type 150 variants. Three samples were subjected to Sangers sequencing and showed wild type pattern.

CONCLUSION

The present study showed that the most common variant in this population was Weak D type 150. This study highlights that serological methods may serve as a screening tool, however, molecular techniques are essential for characterization of RhD variants.

Pattern of distribution of 35 red cell antigens in regular voluntary blood donors of South Gujarat, India

BACKGROUND

Extended phenotyping is one of the important method of reducing red cell alloimmunisation. Extended phenotyping of red cells from voluntary donors have many uses in addition to its application in population genetics. As there was very little data extended phenotyping on a cohort of Indian Voluntary blood donors this project was undertaken.

STUDY DESIGN & METHODOLOGY

200 regular voluntary blood donors having 'O' blood group were included for red cell antigen typing of Rh (D,C,E,c,e), Kell (K, k, Kp^a, Kp^b), Duffy (Fy^a, Fy^b), Kidd (Jk^a, Jk^b), Lewis(Le^a, Le^b), P(P1), MNS (M, N,S,s), and Lutheran (Lu^a, Lu^b), Colton (Co^a, Co^b), Diago (Dia^a, Wr^a), V^w and Xg^a antigens using conventional antisera provided by DIAGAST. Calculations of antigen and phenotypes frequencies were expressed as percentages.

RESULTS

Out of 200 'O' group blood donors, 96.5% were Rh D and 2.5% were K positive. Amongst Rh antigens, e was the most common (100%) followed by D, C (91.0%), c (50.5%) and E (16.5%) with DCe/DCe (R1R1, 48.0%) being the most common phenotype. In Kell blood group system, we found k antigen to be 100% and a rare phenotype Kp (a + b+) was found in 1% of the donors. For Kidd and Duffy blood group systems, Jk (a + b+) and Fy (a + b-) were the most common phenotypes (39.0% and 64.0%, respectively). In the MNS blood group system, M + N+ (67.5%) and S + s+(43.5%) were the most common phenotypes. There were antigens like C^w(3.5%), K(2.3%), Kp^a(1.2%), In^a(1.0%), V^w(1.2%), Co^a(4.5%), Co^b(1%), Lu^a(1.75%), Di^a+(1.2%), and Wr^a+(0.6%) with frequency < 5% in the donor population.

CONCLUSION

Extensively antigen phenotypes group 'O' red cells showed significant variation with other population from India as well as with Caucasian and black population. Extensive phenotyping 'O' group regular blood donors of red cell antigens is very useful to prepare in-house red cell panels for identification of alloantibodies.

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.

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.

Molecular basis and zygosity determination of D variants including identification of four novel alleles in Chinese individuals

BACKGROUND

The frequency and molecular basis of the D variants have been reported in the Caucasian and African populations, but relatively little information was known in the Chinese population. Here, a study was investigated in Chinese persons with weak or discrepant D serologic typing.

STUDY DESIGN AND METHODS

D variant was typed with a serologic method. The full coding regions of RHD of these variants were amplified with polymerase chain reaction and then directly sequenced. RHD zygosity test was performed using the hybrid Rhesus box technique and a multiplex ligation-dependent probe amplification (MLPA) assay was also used to analyze the variant alleles and RHD gene copy number.

RESULTS

Twelve distinct RHD mutation alleles were found in 32 D variant individuals, with eight weak D and four partial D alleles. Weak D Type 15 and DVI Type 3 were the major weak D and partial D alleles in Zhejiang Han persons. Three novel weak D alleles (RHD weak D 95A, 779G, and 670G) and one new partial D allele (RHD130-132 del TCT) were identified. The results of RHD zygosity in three individuals disagreed between the RHD zygosity test and the MLPA assay. The most known variant alleles can be detected, but four novel alleles were missed using the RH-MLPA assay.

CONCLUSION

The molecular basis and zygosity of D variants in Zhejiang Han persons were analyzed, and four novel RHD alleles were identified. These data extend the information of D variants and may help to improve the transfusion strategy of the D variants.

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

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 i.e 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.