anti-A1 Lectin Research Articles

A rare case of ABO grouping discrepancy due to probable blood group switching which presented as lost antigens detectable only with indigenous reagents in less sensitive platforms compared to highly sensitive automated platforms using non indigenous reagents

Abstract: Blood group switching in the form of loss or diminished expression of RBC antigens has been reported in malignancies and infections. Blood group antigens are present on the red cell surface. ABO blood group system is the most clinically significant system. Some cases can present as grouping discrepancy. Here we present a rare case of ABO grouping discrepancy due to probable blood group switching which presented as lost antigens detectable only with indigenous reagents in less sensitive platforms compared to highly sensitive automated platforms using non indigenous reagents. 66 year old female whose historic blood group was A Rh D positive with history of uneventful transfusion of 2 units of A Rh D positive packed red cell one and half years back now presented with mycoplasma pneumonia and acute pulmonary edema. On routine complete blood count testing her hemoglobin was 3.6 gm%, request send to blood bank for pretransfusion testing. Testing performed via conventional tube technique and ABO blood group discrepancy was noted with forward grouping turned to be A Rh D positive (positive reaction with anti A1 lectin) and on reverse grouping 3+ reactions was observed in both A and B cell giving a picture of O blood group. Blood grouping was performed in different platforms including fully automated, semi automated and manual using commercially available antisera and human plasma as a source of anti A, anti B antibodies for forward grouping. The antisera used in automated platforms are non indigenous and that for manual are indigenous. Discrepancy was noted (Forward A and Reverse O) in CTT with commercially available antisera and human plasma as reagents for forward grouping .The same discrepancy was noted with CAT in neutral card with commercially available antisera for manual grouping. But when grouping performed with Column Agglutination Technology using matrix grouping gel card the discrepancy was resolved reporting the blood group as O. For further confirmation we repeated the blood grouping in another fully automated platform, SPRCA Technology (Immucore NEOIRIS) and in that also no discrepancy noted giving a picture of O group. This patient probably had undergone a blood group switching from A to O by losing some but not all A epitopes and started anti A antibody production. Some A epitopes which were not lost had been picked up by the commercially available antisera intended for manual grouping. These antisera are indigenous in origin. Also when human plasma was used as source of antibodies the A epitopes which were not lost were detected. But when grouping was done with non-indigenous antisera in both manual and automatic platform the A epitopes were not detected. This case points towards the relevance of incorporating indigenous antisera in automated platforms.

A Study of A1 and A2 Subtypes Among Whole-Blood Donors With Blood Groups A and AB at the Blood Center of a Tertiary Care Institute in Chhattisgarh.

The ABO blood group shows various subtypes due to the heterogeneity of A and B alleles. The frequency of these subtypes varies in different populations. Studies related to the frequency of subtypes of blood groups A and AB are lacking in this region. So, we planned this study to estimate the prevalence of A1and A2 subtypes among the healthy blood donor population. This was a prospective study performed in the blood center of a teaching hospital in the Chhattisgarh state. Healthy whole-blood donors were included in the study after written informed consent. The conventional test tube method was used for performing forward and reverse blood grouping. Testing with anti-A1 and anti-H lectin was performed in blood groups A and AB. Additional tests such as saliva testing for secretor status and adsorption-elution were performed if needed. Four thousand one hundred twelve donor samples were studied, out of which 1170 showed A antigen. Among 1170 samples, 74.6% were blood group A, and 25.4% were AB. Among blood group A, 92.3% were A1and 3.3% A2,and the rest were other subtypes, while in AB, it was 85.2% A1B and 14.8% A2B. Two cases of anti-A1 antibodies were also noted, which were clinically insignificant. We observed a significantly higher proportion of A2B than A2 in our study population. We also found a large proportion of Aint in the study participants. Testing with anti-A1 andanti-H lectin is recommended in blood groups A and AB to determine various subtypes and prevent any incompatibility.

Prevalence of A2 and A2B Subgroups among Blood Groups A and AB in healthy donors.

To determine the frequency of A2 and A2B subgroups among blood groups A and AB in healthy donors. It was a Cross-Sectional study, conducted at the Department of Hematology & Transfusion Medicine, UCHS, The Children's Hospital Lahore and Sundas foundation Lahore from June 2022 to December 2022 including 13,120 healthy blood donors of both genders, after taking informed consent. Venous blood samples of donors were collected in EDTA vials (3ml) and serum gel vial for routine blood grouping which was done by standard tube method. Further testing of donors positive for an antigen (blood Group-A and AB) was performed using anti-A1 lectin by standard tube method as per manufacturer's instruction. The data was analyzed using SPSS version 23. Among 13120 blood donors, 12857 (97.9%) were male and 263 (2.0%) were female with mean age of 36.7 years ± 15.04 years. Majority of them (91.7%) were of Punjabi ethnicity. Donors having blood group phenotype A and AB were 3890 (29.6%). Among blood Group-A donors, A1 was found in 97.8% and A2 in 2.2% donors. While among Blood Group-AB, 96.7% donors belonged to A1B blood group and 3.2% belonged to A2B blood group. Blood group A2 and A2B do exist in blood donors of Punjabi ethnicity. The knowledge of presence of these blood groups' phenotypes in our population can provide a better base for transfusion staff to do troubleshooting in compatibility testing and to avoid any rare but hazardous transfusion outcome.

Serological and Molecular Characterization of Blood Group A2 in Pakistan

Objective: To determine the frequency of Blood Group A2 genotype among Group A Pakistani whole blood donors.
 Study Design: Cross-sectional study.
 Place and Duration of Study: Armed Forces Institute of Transfusion (AFIT), Rawalpindi Pakistan, from Jan 2019 to Jan 2020.
 Methodology: One thousand (1000) healthy and unrelated blood donors were selected. The blood samples were typed for ABO, and those of Blood Groups-A and AB were further subtyped with the help of anti-A1 lectin to categorize them as A1,non-A1, A1B and non-A1B Groups. Next, DNA of non-A1 samples was extracted, and a Polymerase Chain Reaction using sequence-specific primers (PCR-SSP) for type A2 was performed, followed by polyacrylamide gel electrophoresis (PAGE).
 Results: Among one thousand blood donors, 247(24.7%) were typed as Blood Group-A, 94(9.4%) as AB-Group, 339(33.9%) BGroup and 320(32%) O Group with variable strength of reaction with ABO antisera. A and AB Blood Groups were further subgrouped as A1 202(20.2%), A1B 77(7.7%), non-A1 45(4.5%) and non-A1B 17(1.7%). Anti-A1 antibodies were detected in 6(13.3%) of non-A1 samples. PCR of non-A1 samples showed 32(12.9%) to be genotypically A2, and the remaining 13(5.2%) were not A2 and were not further resolved.
 Conclusion: Blood Group A2 is not a rare Subgroup in our population. PCR-SSP is a more specific technique than anti-A1 lectin for establishing the Blood Group status of an individual.

ABO Genotyping finds more A2 to B kidney transplant opportunities than lectin-based subtyping

ABO compatibility is important for kidney transplantation, with longer waitlist times for blood group B kidney transplant candidates. However, kidneys from non-A1 (eg, A2) subtype donors, which express less A antigen, can be safely transplanted into group B recipients. ABO subtyping is routinely performed using anti-A1 lectin, but DNA-based genotyping is also possible. Here, we compare lectin and genotyping testing. Lectin and genotype subtyping was performed on 554 group A deceased donor samples at 2 transplant laboratories. The findings were supported by 2 additional data sets of 210 group A living kidney donors and 124 samples with unclear lectin testing sent to a reference laboratory. In deceased donors, genotyping found 65% more A2 donors than lectin testing, most with weak lectin reactivity, a finding supported in living donors and samples sent for reference testing. DNA sequencing and flow cytometry showed that the discordances were because of several factors, including transfusion, small variability in A antigen levels, and rare ABO∗A2.06 and ABO∗A2.16 sequences. Although lectin testing is the current standard for transplantation subtyping, genotyping is accurate and could increase A2 kidney transplant opportunities for group B candidates, a difference that should reduce group B wait times and improve transplant equity.

Detection of Clinically Significant Warm Reactive Anti-A1 in a Post Red Blood Cells Transfusion Patient with Acute Lymphoblastic Leukemia

The purpose of this article is to report that some anti-A1 that react at 37°C are IgG antibodies and are clinically significant, as they can cause the destruction of a proportion of A1 cells in vivo following the transfusion of red blood cells. Therefore, when a serum of an individual contains anti-A1, further testing of the plasma against group A1, A2, and O by referencing red blood cells and individual cells against anti-A1 lectin (Dolichos biflorus lectin) must be performed. Confirming the specificity of anti-A1 by referencing red blood cells is also important in selecting the appropriate blood for transfusion. ABO antibodies are naturally occurring and activate the complement cascade, making them more likely to cause severe transfusion reactions compared to antibodies to other RBC antigens.

A Case of Blood Group A2B with Anti A1 Antibody Reactive at 37°C

Landsteiner discovered ABO blood group system. It is most important for transfusion medicine. Blood group A has several subtypes and most important are A1 and A2, upon which further groups of A and AB have been classified as A1, A2 and A1B, A2B. Of individuals with A antigen, approximately 20% belong to A2 while rest 80% belong to A1. Anti-A1 Lectin, a cold agglutinin which destroys A1 cells is clinically significant when they react at 37°C, causing transfusion reactions. Bangladesh J Medicine 2022; 33: 312-316

Molecular genetic analysis reveals a novel B variant allele at the ABO locus

BackgroundWhen discrepancies in ABO blood typing emerge, ABO subgroups should be considered. Serological procedures such as the adsorption-elution test, the salivary ABH inhibition test, and the antiA1 (lectin) saline technique might be employed. These serological approaches, however in rare blood types are difficult to understand. As a result, a dependable and cost-effective approach for determining ABO subgroups is of special relevance. Methodologyfor this purpose, DNA sequencing is most reliable solution for accurate results. Exon 1 to 7 5′ 3’ UTR and intron 6 of ABO gene of a Chinese individual was sequenced because the laboratory was unable to determine the blood group by traditional method. ResultsThe analysis of the blood showed weak B antigens on their surface. Gene sequencing results revealed a novel B allele, that has one novel identified nucleotide difference from T to C at nucleotide 425. ConclusionThe results reported novel B allele which cannot be confirmed by conventional serological methods. Owing to the peculiarity of ABO blood types of inheritance, findings on the incidence and molecular causes of rare blood groups in the Chinese population have substantial therapeutic implications and are worthy of additional investigation in the future.

Prevalence of Blood Group A2 in Northern Pakistan

Objective: To determine the prevalence of A1 and A2 subgroups of blood group A in healthy blood donors of northern Pakistan.
 Study Design: Cross sectional study.
 Place and Duration of Study: Armed Forces Institute of Transfusion, Rawalpindi Pakistan, from Sep to Dec 2017.
 Methodology: The blood samples of donors reported during the study period at Armed Forces Institute of Transfusion were collected. ABO typing was performed and those in group A and AB were further subtyped using anti-A1 lectin and thus the individuals were labelled as A1 (and A1B) or A2 (and A2B). The serum of individuals with groups A2 and A2B was tested for anti-A1 based on the reaction with A1 red cells.
 Results: Out of total 4485 donors, 1116 (24.88%) were of blood group A and 422 (9.41%) individuals were of AB group. Out of 146 (13.08%) individuals among 1116 blood group A donors were of subgroup A2. While out of 422 of blood group AB, 80 (18.95%) were A2B. 21 (14.38%) out of 146 individuals of A2 blood group, had anti-A1 antibody while among 80 individuals with A2B blood group only 2 (2.50%) had anti-A1 antibody in their serum.
 Conclusion: Blood group A2 is quite prevalent in our population. Although anti-A1 is present in significant fraction of A2 blood group individuals, the routine testing is not needed to identify the A2 group and cross match compatibility is the only requirement as anti-A1 is rarely active at 37° C.

A1 and A2 subtypes of blood group A

Objective To determine the prevalence of A1 and A2 blood subgroups and detect anti-A1 antibodies in the studied population to assess their implication in transfusion practice. Background The A blood type contains ∼20 subgroups, of which A1 and A2 are the most common. The distinction between the A1 and A2 subgroups is usually made by using anti-A1 lectin. A2 and A2B subgroups might have anti-A1 antibody, which become clinically significant if they react at 37°C and may lead to hemolytic transfusion reaction. Patients and methods Blood samples were collected from 10 662 participants attending Fayoum University Hospital Blood Bank over a period of 8 months. Analysis of ABO and Rh-D blood groups using column-agglutination technique was done. Subgrouping using anti-A1 lectin was performed for A and AB blood groups. Anti-A1 antibodies detection using AHG microcolumn was done for A2 and A2B subgroups. Results Blood group A was present in 40.1% (4274 participants), of whom 39.8% were A1 and 0.3% were A2, whereas group AB was present in 7.8% (836 participants), of whom 6.3% were A1B and 1.5% were A2B. Anti-A1 antibodies were not detected in any of the subgroups A2 and A2B. Conclusion Despite the large population sample of this study, A2 and A2B are rare subgroups and were only found in 195/10 662 (1.8%) of studied samples, and anti-A1 antibodies were not detected. However, implementation of A1 and A2 grouping is vital to avoid any reactions that could occur from these minor incompatibilities, leading to overall improvement in blood transfusion practice.

A close aspect of recognizing and resolving blood group discrepancy carried in a tertiary hospital, Bangladesh

Aims: Blood grouping includes both forward and reverse typing and there is always an inverse reciprocal relationship between this. Any unusual reaction can confer discrepancy and may lead to grave incompatible transfusion reaction. Resolving discrepancy is a crucial part that should not be ignored to save patients life. Methods: It is a cross-sectional study carried out at a tertiary hospital, over a period of one year. Sample had been selected based on comprehensive history, medical records, physical findings, and laboratory reports. ABO and Rh typing was done by using monoclonal immunoglobulin M (IgM) reagents (Tulip, Lorne and Biorex Diagnostic Ltd.) and A, B, and pooled O cell. Therefore, anti-H and anti-A1 lectin, extended red cell phenotyping, Coombs analysis had also done in few suspected cases. Results: A total 25,082 blood group testing was done, 318 samples were carried out for group confirmation and discrepancy found in 51 cases. Technical and clerical errors were found in 18 cases. The remaining 33 samples reported as true discrepancy which was detected by Coombs analysis (both direct and indirect), antibody screening, determination of Rhesus genotype and phenotype, and minor antibody detection. The rate of discrepancy is about 0.20%. Meanwhile, missing antigen was found in 3 cases (5.88%), missing antibody in 1 (1.96%), additional reaction due to rouleaux’s in 4 (7.84%), mixed field (mf) reaction due to mismatched blood transfusion in 6 (11.76%), alloantibody with mixed phenotype in 5 (9.80%), cold antibody in 9 (17.24%), and Bombay in 5 cases (9.80%). Conclusion: Blood group discrepancy is not an uncommon phenomenon. All the critical issues should be sensibly explored, evaluated, and analyzed by the expert physicians to avoid the discrepancy. These common but curable issues can be easily carried out and solved. A careful surveillance can also play a significant role in monitoring the recuperate misidentification problem. Therefore, all the technical staffs who usually play these vital roles should be mannered and clarified in a successful motion, to avoid this type of discrepancies.

Initiative for rare donor registry for A2/A2B subgroups with Rh phenotyping: A first of its kind

Aims: Aim of this study is to create donor registry of A2/A2B subgroup blood donors with Rh and Kell phenotype, to provide transfusion to multi-transfused A2/A2B subgroup patients and to prevent adverse transfusion reaction due to immunological stimulation by pre-existing anti-A1 antibodies having enhanced titer and thermal amplitude. Prevalence of A2/A2B subgroup in Indian population is rare with highest prevalence of “e” antigen among the five Rh antigens, phenotyped serologically, and “E” antigen being the lowest in prevalence. Anti-A1 antibodies appear as cold agglutinins in A2/A2B individuals and can be clinically significant when reactive at 37 °C, causing hemolysis of A1 RBCs. Methods: A retrospective data analysis was done in a tertiary care hospital-based blood center at capital city of India from January 2016 to December 2020. All donors were subjected to ABO Rh grouping, Rh and Kell phenotyping by solid phase method. Tube technique was used to distinguish A2/A2B by agglutination reaction with anti-A1 lectin. Results: Total 40,051 donors were analyzed during study period, of which, A and AB groups constituted 21.26% and 9.01% respectively; out of these, only 0.47% belonged to A2 subgroup while A2B subgroup was more frequent (1.06%). The rarest Rh phenotypes found were R1Rz, r”r, r’r” in A2/A2B blood donors. Conclusion: There is a need to create rare donor registry for A2/A2B subgroups and clinically significant blood group antigens and share at various levels. This is a first small step to create a rare donor registry of A2/A2B subgroups with Rh and Kell phenotype, to provide transfusion to A2/A2B patients to prevent adverse transfusion reaction due to immunological stimulation by pre-existing anti-A1 antibodies having enhanced titer and thermal amplitude and to ensure improved quality of transfusion therapy.

Prevalence of A2 and A2B Subgroups and Anti-A1 Antibody in Blood Donors in Jazan, Saudi Arabia.

PurposeA2 and A2B are rare phenotypes of the ABO blood group system. Some individuals with A2 and A2B may have anti-A1 antibodies that may be clinically significant or insignificant. The aim of this study was to determine the frequency of A2, A2B phenotypes and anti-A1 antibodies in blood donors in Jazan, Saudi Arabia. This study also evaluated the reactivity potential of anti-A1 antibodies.Materials and MethodsBlood samples collected from 446 blood donors were typed for ABO (cell and serum grouping) and Rh D. Individuals with blood group A and AB were further subtyped by testing with anti-A1 lectin. In addition to the serum grouping using A1 red cells, A2 and A2B individuals were screened for the presence of anti-A1 in their sera against A1 red cells at 4°C, 22°C and 37°C to determine the thermal amplitude of the reacting anti-A1 antibody (if present).ResultsAmong A and AB, A1 was the commonest phenotype (20.2%, n=90 out of 446) while A1B was found to be 1.8% (n=8) among AB phenotype. A2 and A2B were found to be 2.2% (n=10) and 0.9% (n=4), respectively. Only one individual with A2B blood type showed cold reactive anti-A1 antibody, the strength of which was 32.ConclusionA2 and A2B were the rarest among ABO phenotypes in the studied population. Although rare, anti-A1 antibody is not so uncommon. Care shall be taken during routine ABO grouping especially in cases of mix-field or weak positive reactions in A and AB phenotypes.

Absence of 1061C deletion in A2 blood subgroup validated through gene sequencing in the Malaysian population

ABO blood grouping is an important antigenic blood typing tools in blood transfusion and organ transplants. Mismatching of blood during transfusion would lead to undesired transfusion reactions. Due to rare occurrence of rare blood group such as A2 subtype, regular blood grouping technique would have missed the identification of blood group. In this study, the identification of A2 subgroup using routine serological technique was validated via DNA sequencing technique. A total of 656 students participated in this study consist of Malay (87.0 %), Chinese (0.4 %), Indian (11.4 %) and others ethnic group (0.9%) respectively. Monoclonal antisera A, B, AB, D, A1 lectin and H lectin were used to identify the antigen on red blood cells. DNA sequence analysis was applied to examine single nucleotide polymorphisms (SNPs) at position 467 (substitution of C>T) and 1061 (deletion of C) on coding region of ABO gene. Our findings showed of 656 blood samples, 256 (39.0%) were blood group O, 190 (29.0%) were blood group B, 179 (27.3%) were blood group A and 31(4.7%) were blood group AB. The frequency of A1 subgroup is 177 (99.0%) and A2 subgroup is 2 (1.0%). From 179 A blood group, only 2 samples showed negative reaction towards anti-A1 lectin. DNA sequence analysis revealed the SNPs at nucleotide 1061 position in sample 2, however sample 1 did not have this mutation and the subgroup was not identified. DNA sequencing provides a precise and high accuracy in identification of A subgroups.

A CASE REPORT ON UNCOMMON A2 SUBTYPE OF BLOOD GROUP A

Blood group A has various subtypes with A1 being the most common. A2 and other weaker subtypes are less commonly encountered. The differentiation between A1and A2 is based on the reactivity of A1 cells but not A2 cells with anti-A1 lectin. A2 cells show increased reactivity with anti-H lectin. The incidence of A2 subtype is not known in this region. Here, we report an incidental case of A2 blood group in a 25-year male. Subgroups of blood group A can result in ABO blood group discrepancy and rarely may lead to hemolytic transfusion reactions. The case report highlights the need to be aware of such uncommon and rare blood groups and using anti-A1 lectin as a standardized protocol to prevent blood group incompatibility.

P106 LinkSēq for ABO, a molecular based typing solution for the ABO blood group

Aim ABO-incompatible (ABOi) organs have been successfully transplanted from A2 donors into B recipients, especially when the recipient’s anti-A titers are reduced. Laboratories typically use serological methods to perform ABO typing. However, serology has significant limitations including (i) recently transfused patients may exhibit mixed field agglutination and (ii) both forward and reverse typing must be performed, but may yield discordant results. These limitations are most problematic with phenotypes involving weakly expressed antigens and ABO subgroups (i.e. A2). However, current ABO subgrouping methods using anti-A1 lectin have limitations: they only indirectly determine A2, and typically include a gray zone reactivity range for which subgroups cannot be reliably called. A combination of genotyping solutions (SSP, sequencing, etc) can be used for ABO subgrouping, but these methods are time- and labor-consuming, and require interpretation by subject matter experts. Methods The Thermo Fisher Scientific solution is based on its LinkSēq real-time PCR technology, which was developed over 10 years ago for genotyping the complex Human Leukocyte Antigen (HLA) system. LinkSēq ABO analyzes 19 reactions that identify multiple relevant SNPs located within the ABO gene. We evaluated this solution by analyzing 40 archived DNA samples, including blood blank samples for which serotyping failed or produced discordant results, and samples from deceased solid organ donors for comparison with A1 lectin testing. Results Genotyping results generated by LinkSēq were 100% concordant with typing obtained by traditional methodologies. In two cases, serology couldn’t provide conclusive results and typing had to be reflexed to lectin tests or SBT. LinkSēq overcomes the major challenges of molecular typing by providing a robust, automated approach that increases laboratory productivity and reduces turn-around time. With less than 10 min of hands-on set-up, no further operator intervention with reagents, and SureTyper software fully automating all analysis, LinkSēq delivers genotyping and predicted phenotyping results in approximately 90 min. Conclusions We conclude that LinkSēq can provide a simple, effective and robust method for ABO typing including accurate A2 subgrouping.

Rapid rare ABO blood typing using a single PCR based on a multiplex SNaPshot reaction.

ABO subgroups would be considered when discrepancies in ABO grouping occur. Serological methods including adsorption-elution test, salivary ABH inhibition test, and anti-A1 (lectin) saline method could be used. However, these serological methods are laboring and obscure. Therefore, reliable and affordable method to assess the ABO subgroups is of particular interest. To solve this problem, the multiplex SNaPshot-based assays were designed to determine rare A and B subgroups. Primers used as probes for determination of rare ABO blood groups known in Taiwanese population were designed. Many ABO subtype samples were used to validate the accuracy and reproducibility of our SNaPshot panel. A panel of primer probes were successfully designed in determining 8 SNP sites (261, 539, 838, 820, 745, 664, IVS6 +5, and 829 in exon 6 and 7) for A phenotype and 6 SNP sites (261, 796, IVS3 +5, 247, 523, and 502 in exon 2, 6 and 7 and intron 3) for B phenotype. SNaPshot analysis for defining blood group A alleles (A1, A2, A3, Am and Ael) and blood group B alleles (B1, B3, Bw and Bel) was therefore available. SNaPshot analysis could be used in reference laboratories for typing known rare subgroups of A and B without DNA cloning and traditional sequencing. Moreover, this method would help to construct databases of genotyped blood donors, and it potentially plays a role in determining fetal-maternal ABO incompatibility.

Anomalous blood grouping showing red cell mosaicism in a patient with acute leukemia

Background: The ABO blood groups are determined by forward grouping on red cells and are confirmed by reverse grouping on serum, both of which must tally to assign proper blood group to an individual. Any anomaly in blood group must resolve before transfusion. Aim: A patient with anomalous blood grouping required to be investigated as pretransfusion tests. Materials and Methods: ABO blood grouping protocol was followed. The patient's red blood cells (RBCs), showing mixed-field reaction, were separated into those showing agglutination from other remaining nonagglutinated RBCs by selective adsorption using anti-A1 lectin and subsequently disagglutinated by incubating with soluble salivary antigen from Group A secretor individual. Results: Of the two RBCs populations, one that was agglutinated by the lectin showed considerably stronger agglutination with anti-A antibody as compared to those that were not agglutinated. Conclusion: Weakened red cell A antigen was presumed to be due to underlying disease process in acute leukemia.

A1 and A2 Sub-Types of Blood Group ‘A’: A Reflection of their Prevalence in North Karnataka Region

Landsteiner ABO system of blood groups is most important for transfusion medicine and has subtypes of A Antigen, A1 and A2, upon which further groups of A and AB have been classified. Of individuals with A antigen, approximately 20% belong to A2 while rest 80% belong to A1. Anti-A1 Lectin, a cold agglutinin which destroys A1 cells is clinically significant when they react at 37°C, causing transfusion reactions. To assess the prevalence of A1 and A2 subgroups in the population. This was two year retrospective analysis of blood groups of donors coming to the blood bank of Karnataka Institute of Medical Science, Hubli, Karnataka, India. The data of the subgroups A and AB was analysed. 20,864 donors were analysed. Of 5466 (26.20%) of A group, 5406 (98.90%) belonged to A1 subgroup and only 60 (1.10%) belonged to A2 subgroup. Of 1708 donors with blood group AB, 1532 (89.70%) belonged to A1B subgroup and 176 (10.30%) belonged to A2B. It was noted that A2 in AB blood-group, as A2B, was more frequent in occurrence than presence of A2 as an A blood group. Rhesus negative frequency in these subgroups was also reported. Having known the prevalence of A1 and A2 subgroups and incorporating them into the ABO grouping system can limit these minor, yet dangerous, transfusion incompatibilities.

English

Polymorphisms in the genes coding for A gene leads to subgroups of A. No published data regarding the prevalence of subgroups of A blood group in Andhra Pradesh, India is available. The importance of subgrouping is that the A antigens in various subgroups may differ both quantitatively and qualitatively 1 . Some individuals with blood groups A2, A3, Ax, Ael, Aend, A2B etc., have anti-A1 antibodies and may present problems in blood grouping. At our center, the typing of A subgroup of all blood donors was done using commercial anti A1 lectin, anti-A and anti-AB antisera as per the manufacturer’s instructions. On analysis of a total of 5,505 blood groupings over a period of one year, 1,486(27%) individuals had A antigen. Of these, 1,137 (20.7%) were typed as A group and 349 (6.3%) as AB group based on the presence of associated B antigen. Of the 1,137 A group individuals,1,090(95.9%) had A1 antigen (subgroup A1) and the rest 47(4.1%) had no detectable A1 antigen (subgroup A2). Similarly among the 349 AB group individuals, 282(80.8%) had A1 antigen (subgroup A1B) and 67(19.2%) had no detectable A1 antigen (subgroup A2B). The number of individuals who lack A1 antigen is less among A group individuals in contrast to AB group individuals and this difference was found to be statistically significant (p<0.0001). This may be due to the recessive nature of A2 gene compared to A1 gene and requirement of a single A2 gene and a B gene to develop as A2B blood group phenotypically and two A2 genes or one A2 gene and one O gene to develop as A2 blood group. Some postulate the presence of a strong B gene that would suppress A1 antigen activity. 2 No other subgroups of A could be detected in the present study due to the small number of donors phenotyped for subgroups of A. Similar results were obtained in other studies from Karnataka 3 and Japan. 4 By including a much larger population, the frequency of other A subgroup antigens can also be estimated. In the present study, the prevalence of A2 and A2B sub groups was found to be 0.85 percent and 1.21% in blood donors respectively. REFERENCES 1. Thakral B, Saluja K, Bajpai M, Sharma RR, Marwaha N. Importance of weak ABO subgroups. Lab Med 2005;36:32-4. 2. Voak D, Lodge TW, Reed JV. A possible explanation for the expression of A2B phenotypes observed in some populations. Vox Sang 1970;18:471-4. 3. Shastry S, Bhat S. Imbalance in A2 and A2B phenotype frequency of ABO group in South India. Blood Transfus 2010;8:267-70. 4. Ogasawara K,Yabe R, Uchikawa M, Saitou N, Bannai M, Nakata K, et al. Different alleles cause an imbalance in A2 and A2B phenotypes of the ABO blood group. Vox Sang 1998;74:242-7. I.S. Chaitanya Kumar, A. Yashovardhan, B. Suresh Babu, Anju Verma, K.V. Sreedhar Babu, DS Jothi Bai. Department of Immuno Haematology and Blood transfsion, Sri Venkateswara Institute of Medical Sciences, Tirupati.