Molecular analysis and transfusion management in a rare case of cis-AB blood group: A report from India.

Molecular characterization of a rare cis-AB blood group has not been done in the Indian subcontinent. Herein, we report a case of A2B3 blood group in an Indian patient which was subsequently confirmed to be a case of cis-AB phenotype. Blood grouping was performed by the column agglutination technique (CAT), conventional tube technique (CTT) and subsequently, whole exome sequencing for molecular analysis. The patient was initially typed as AB, RhD positive in forward grouping. However, serum grouping showed agglutination (2+) with the B red cells in CAT. In CTT, an extra reaction was observed with A1 red cells and a strong agglutination was seen with Anti-H lectin. Thus, the blood group was identified serologically as A2B3. During the next-generation sequencing, a total of 10 exonic variants in the ABO gene were filtered, of which 2 (rs8176747 and rs7853989) were found to be non-synonymous and occurring on the same allele. The other allele was found to be ABO*A1.01. The sample analyzed in the study was found to carry two previously reported nucleotide changes of cis-AB (c.803G > C and c.526C > G) on the same allele which had not been reported before. Transfusion requirement was managed with type O red cells and type AB plasma.

Analysis of ABO grouping discrepancies among patients from a tertiary hospital in Korea.

BACKGROUND: Accurate ABO typing is essential for preventing ABO incompatibility reactions. However, the causes of ABO grouping discrepancy has not been sufficiently studied, and it may vary among different ethnic populations. Thus, the aim of this retrospective study was to investigate the causes of ABO discrepancy in the East Asian population. MATERIALS AND METHODS: A retrospective observational study on ABO typing discrepancy among patients in a tertiary hospital was carried out using the electronic medical record database of Samsung Medical Center (Seoul, Korea) between July 2016 and May 2019. RESULTS: ABO grouping was performed on 551,959 blood samples during the study period; 1468 events of serologic ABO discrepancy were determined from 1334 (0.24 %) samples. A total of 134 samples (0.02 %) presented multiple causes of ABO discrepancy. Weak/missing serum reactivity (594, 40.5 %) was the most frequent reason for ABO discrepancy, followed by extra serum reactivity (370, 25.2 %), weak/missing red cell reactivity (267, 18.2 %), mixed-field red cell reactivity (176, 12.0 %), and extra red cell reactivity (61, 4.2 %). In the category of weak/missing red cell reactivity, ABO subgroup was the most common reason, and using ABO genotyping, 26.2 % of the cases genotyped were found to be related to the cis-AB allele. CONCLUSIONS: Our results suggest that the incidence and cause of ABO typing discrepancies vary among institutes and ethnic groups. Our data helps to better understand and facilitate the resolution of ABO typing discrepancies in patients.

Cis-AB, the Blood Group of Many Faces, Is a Conundrum to the Novice Eye.

Cis-AB, a rare ABO variant, is caused by a gene mutation that results in a single glycosyltransferase enzyme with dual A and B glycosyltransferase activities. It is the most frequent ABO subgroup in Korea, and it occurs more frequently in the East Asian region than in the rest of the world. The typical phenotype of cis-AB is A2B3, but it can express various phenotypes when paired with an A or B allele, which can lead to misclassification in the ABO grouping and consequently to adverse hemolytic transfusion reactions. While cis-AB was first discovered as having an unusual inheritance pattern, it was later found that both A and B antigens are expressed from the same allele inherited from a single parent; hence, the name cis-AB. Earlier studies relied on serological and familial investigation of cis-AB subjects, but its detection has become much easier with the introduction of molecular methods. This review will summarize the serological variety, genetic basis and inheritance pattern, laboratory methods of investigation, clinical significance, and the blood type of choice for transfusion for the cis-AB blood group.

ABO Mistyping of cis-AB Blood Group by the Automated Microplate Technique.

BACKGROUND: The cis-AB phenotype, although rare, is the relatively most frequent of ABO subgroups in Koreans. To prevent ABO mistyping of cis-AB samples, our hospital has applied a combination of the manual tile method with automated devices. Herein, we report cases of ABO mistyping detected by the combination testing system. METHODS: Cases that showed discrepant results by automated devices and the manual tile method were evaluated. These samples were also tested by the standard tube method. The automated devices used in this study were a QWALYS-3 and Galileo NEO. Exons 6 and 7 of the ABO gene were sequenced. RESULTS: 13 cases that had the cis-AB allele showed results suggestive of the cis-AB subgroup by manual methods, but were interpreted as AB by either automated device. This happened in 87.5% of these cases by QWALYS-3 and 70.0% by Galileo NEO. Genotyping results showed that 12 cases were ABO*cis-AB01/ABO*O01 or ABO*cis-AB01/ABO*O02, and one case was ABO*cis-AB01/ ABO*A102. CONCLUSION: Cis-AB samples were mistyped as AB by the automated microplate technique in some cases. We suggest that the manual tile method can be a simple supplemental test for the detection of the cis-AB phenotype, especially in countries with relatively high cis-AB prevalence.

A novel cis-AB variant allele arising from a de novo nucleotide substitution c.796A>G (p.M266V) in the B glycosyltransferase gene.

BACKGROUND: Cis-AB, a rare ABO variant, is the result of a mutated ABO gene that produces a glycosyltransferase enzyme with dual A and B glycosyltransferase activity. It may lead to ABO discrepancies and a delay in establishing the blood group. To date, there have been no reports of a de novo mutation leading to a cis-AB allele. OBJECTIVES AND METHODS: Sequencing of the ABO gene using blood and hair follicle cells from the proposita were performed along with blood from her parents. To establish maternity and paternity, short tandem repeat (STR) analysis was also performed. The A and B enzyme activities of the novel enzyme were measured in an in vitro expression study. RESULTS: A novel cis-AB allele arising from nucleotide substitution c.796A>G (p.M266V) in the B glycosyltransferase gene were discovered in the blood and hair follicle cells from the proposita, which was absent from her parents. In all 15 autosomal STR loci analysed, the probability of maternity and paternity were 0.999999 and 0.999989, respectively. The novel enzyme created 33.1% and 60.2% of A and B antigen compared to wild type A and B glycosyltransferases. CONCLUSION: A novel mechanism leading to a cis-AB allele was discovered.

A Case of ABO* cis-AB01/Ax03 Found in A2B3 Phenotype / 대한수혈학회지

The cis-AB blood group is rare; however, it is relatively more common in the Korean and Japanese populations. Among nine cis-AB alleles, only the cis-AB01 allele has been reported in the Korean population. When the A2B3 phenotype is found, it has the cis-AB01/O genotype; to date, it has not been reported in any other genotype. Here we report on an extremely rare case of cis-A2B3 found in the cis-AB01/Ax03 genotype. EDTA samples of a 52-year-old male with hepatocellular carcinoma and his family were sent to our laboratory. Standard ABO typing and sequencing of exons 6 and 7 of the ABO gene of the propositus and his family were performed: the propositus with the A2B3 type had cis-AB01/Ax03, brother with O type had O01/O02, sister with O type had Ax03/O01, son with B type had Ax03/B101, and daughter with A1B3 type had cis-AB01/A102. Results based on family study and genotyping revealed that the propositus had both cis-AB01 and Ax03 alleles. This is the first case of A2B3 phenotype with cis-AB01 with an allele other than the O allele in the cis-AB blood group reported so far.

Characteristics of Intron 6 Nucleotide Sequences of cis-AB in Koreans / 대한수혈학회지

BACKGROUND: The cis-AB is a very rare phenotype in the ABO blood group system. It corresponds to a special ABO allele that encodes glycosyltransferase that is capable of synthesizing both A and B antigens. Until now, the exon 6 and 7 gene sequences of cis-AB alleles are well known. In this study, we report on the intron 6 sequence structure of the cis-AB allele. METHODS: Standard serologic tests for the ABO blood group phenotypes were performed in four cis-AB samples. Allele-separation by cloning and subsequent sequencing was carried out. RESULTS: The results showed that intron 6 of cis-AB is almost identical to the A101 allele except for three single nucleotide polymorphisms at nucleotide positions 163, 179 and 662, where the nucleotides of the A101 replace those of B101. CONCLUSION: The intron 6 sequences of cis-AB in Koreans have both A101 and B101 blood group sequences.

A Transfusion Experience for a Patient with Cis-A2B3 Phenotype / 대한수혈학회지

We report the case of a 64-year-old man presenting to the hospital for treatment of his anemia. Exact ABO blood typing is an essential step to prevent transfusion reactions. The selection of the wrong blood component for transfusion can be a clinical problem and in this case the patient had a cis-AB blood type that could have caused an ABO discrepancy. In this case neither autologous or directed blood transfusion was possible and O+ red blood cell was transfused without a transfusion reaction.

A Case of a Family with a High Frequency of cis-AB / 대한수혈학회지

The cis-AB phenotype is relatively common in the Japanese and Korean populations. Phenotypes of cis-AB include variables such as A2B3, A2B and A1B3. A few cases of cis-AB with phenotype A1 have been reported. Recently, we experienced a case with one family member identified with phenotype A1, genotype cis-AB/A and a high frequency of cis-AB. A 34-year-old woman visited the hospital for prenatal testing. The ABO phenotype of the patient was A2B3. To confirm the presence of cis-AB, ABO typing and genotyping of the patient's family were performed. The patient's mother and father were typed as normal group O and A, respectively. The ABO genotype of the mother was identified as cis-AB/A. The four sisters and brothers were typed as cis-AB. The normal incidence of cis-AB in a family is 50%. Interestingly, ABO typing revealed that all five members of the family had cis-AB in this case.

Mismatched Transfusion Reaction in cis-AB: A case report / 대한마취과학회지

AB blood group is determined by A and B genes located on each chromosome which inherited from parents. But unusual inheritance of A and B genes on the same chromosome has been reported as cis AB. Recently the authors have experienced one case of patients with cis AB blood type undergoing emergency adhesiolysis of small bowel obstruction. We transfused the patient with Rh A+ packed red blood cell and fresh frozen plasma with atypical delayed hemolytic transfusion reaction.

ABO Gene Analysis of Discrepant ABO Blood Group in Blood Donors / 대한수혈학회지

BACKGROUND: An exact ABO blood group is essential for prevention of transfusion accident and safe transfusion therapy. It is known that one of causes of ABO discrepancies is ABO subgroup caused by genetic polymorphism. Therefore, we analyzed ABO genotype of ABO discrepancies in blood donors and studied the distribution and cause of ABO discrepancies. METHODS: This study examined 118 samples showing ABO discrepancies of ABO blood typing between May 2003 and Dec 2003. ABO genotyping using the polymerase chain reaction-restriction fragment length polymorphism(PCR-RFLP) method was performed on 118 samples. Restriction enzymes including BssH II, Kpn I and Alu I were used for PCR-RFLP. RESULTS: The genotypes of 118 cases were composed of 43 cases of A/B, 12 cases of A/O, 10 cases of B/O, 1 case of B/B, 37 cases of cis-AB/O, 4 cases of cis-AB/A, 11 cases of cis-AB/B. The genotype of cis-AB/O showed 32 cases with phenotype A2 B3 , 2 cases with phenotype A2 B, 2 cases with phenotype A1 B3 , 1 case with phenotype Ael B. The genotype of cis-AB/B showed 11 cases with phenotype A2 B, and cis-AB/A showed 2 cases with phenotype A2 B3 , 1 case with phenotype A1 Bx and 1 case with phenotype A1 Bel. CONCLUSION: These data demonstrated that the most frequent genotype of ABO discrepancies in our study is cis-AB. The most predominent phenotype of cis-AB/O is A2 B3 . ABO genotyping is useful in resolving ABO discrepancies, and determination of ABO subgroups.

The frequency of the cis-AB blood type in blood donors in southwestern Korea / 대한수혈학회지

BACKGROUND: Cis-AB is a rare ABO blood type with an unusual inheritance, on the same chromosome that results from a point mutation. It is relatively common in Korean and Japanese populations. Although more than 100 cases of the cis-AB blood type have been reported, there is no report on the frequency of the cis-AB blood type in Korea. Therefore, we analyzed the frequency of the cis-AB blood type in blood donors in southwestern Korea. METHODS: This study examined 111,842 samples obtained from blood donors recruited at the Gwangju-Chonnam Red Cross Blood Center between July 2002 and Oct 2002. ABO serologic tests were performed on all of the samples and ABO genotyping using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method was performed on peripheral blood DNA samples from 129 cases: 24 A2B3, 81 A2B, 23 A1B3, and 1 A1Bx or el case. RESULTS: The frequency of the cis-AB blood type was 0.0331%(37/111,842). Of the 37 cases, 24 cases were the cis-AB/O genotype with the A2B3 phenotype, 9 cases were the cis-AB/A genotype with the A2B phenotype, 3 cases were the cis-AB/B genotype with the A1B3 phenotype, and 1 case was the cis-AB/A genotype with the A1Bx or el phenotype. In the 129 cases, the cis-AB ratio was 100% (24/24), 39.1% (9/23), 3.7% (3/81), and 100% (1/1) in the A2B3, A1B3, A2B, and A1Bx or el phenotypes, respectively. CONCLUSIONS: The frequency of the cis-AB blood type in blood donors in southwestern Korea is about 0.0331%. The most common type of cis-AB was cis-AB/O with the A2B3 phenotype. In addition, one case of cis-AB/A with an unusual A1Bx or el phenotype was found.

Phenotype and Genotype of Cis-AB Family in Chonnam Area / 대한수혈학회지

BACKGROUND: Cis-AB is a rare blood ABO with unusual inheritance on the same chromosome that result from a point mutation. It is relatively common in Korean and Japanese populations. We analyzed serological and molecular genetic characteristics of the family with cis-AB who had visited Chonnam National University Hospital (CNUH) for 10 years. MATERIAL AND METHODS: The subjects of this study comprised 88 samples derived from cis-AB family of 17 propositi with A2B3 phenotype diagnosed at CNUH between January 1993 and May 2002. Serologic tests for cis-AB were performed in detail on the ABO antigens of 49 samples, polymerase chain reaction - restriction fragment length polymorphism (PCR-RFLP) method for cis-AB genotyping was additionally performed in peripheral blood DNA samples from 19 cases. RESULTS: The phenotypes of 49 cases were composed of 39 cases of A2B3, 7 of A2B, 2 of A1B3 and 1 of A1. ABO genotype on the blood samples from 19 cis-AB cases showed 11 cases of cis-AB/O with phenotype A2B3, 6 of cis-AB/B with phenotype A2B, 1 of cis-AB/A with phenotype A1B3 and 1 of cis-AB/A with phenotype A1. CONCLUSIONS: These data demonstrated that the most frequent type of cis-AB cases in Chonnam area was cis-AB/O with phenotype A2B3 and a case of cis-AB/A with unusual A1 phenotype was found.

A Case of Cis-AB without B Antigen Expression / 대한수혈학회지

The cis-AB bood type is a rare phenomenon in which both the A and B blood types are inherited from a single parent. The cis-AB persons are not homogeneous with respect to reactivity of their red cells to anti-A and anti-B reagents, and are split into three groups with on the basis of the strength and characteristics of the serologic reactions; these reactivities are A2B3, A1B3 and A2B. A 7-year-old Korean boy was evaluated for paternity because he was presumptively identified as blood group AweakB and known blood types of his father and mother were A. In the repeated ABO blood typing, the child was typed as group A2B3 with weak anti-B, cis-AB being suspected. Both of his mother and father were typed as group A1 in cell and serum typing. In the saliva test and adsorption and elution studies of the parents, B substance was not detected. According to ABO genotyping, the child, mother and father showed cis-AB/O, A1/O and cis-AB/A1, respectively. The paternity was confirmed, but the father had unusual expression of cis-AB genotype. This was the second case of A1/cis-AB with phenotype A1, not expressing B antigen.

Unusual Phenotype Expression in a Cis-AB Trait: Cis-AB Child from a Group A Father and a Group O Mother / 대한수혈학회지

Cis-AB (A2B3) is a rare genotype resulting from the inheritance of both A and B genes on one chromosome. Among possible genotypes of cis-AB, in individuals with O/cis AB and A1/cis-AB, the B antigen is usually weakly expressed. Study on a blood sample from a 13-year-old Korean girl showed a discrepancy between red blood cell and serum typing. The blood type was identified as AweakB on the red cell test, while weak anti-B was detected in the serum. Cis-AB (A2B3) was suspected, however, known blood types of her father and mother were A and O, respectively. In the repeated test, the propositus was typed as group A2B3. Her mother was typed as normal group O. Her father was typed as group A1 in cell typing, but in his serum, anti-B was very weakly detected. In the saliva test and adsorption and elution studies of the father, B substance was not detected. Finally, ABO genotyping was performed and ABO genotypes of the patient, mother and father were cisAB/O, O/O and cisAB/A1, respectively. This was the first reported case of A1/cisAB with phenotype A1. ABO genotyping technique will resolve problems encountered in association with unusual phenotype expression of cis-AB trait.

ABO gene analysis of cis-AB and B subgroup in blood donors / 대한수혈학회지

BACKGROUDS: Based on elucidation of genetic basis of ABO blood group, the genetic mutation of blood subgroup has been investigated. Especially, the discovery of base substitution such as C467T, G803C in cis-AB have made the efforts to determine cis-AB blood group by molecular method. This study was performed to investigate the ABO gene structure and usefulness of genotyping method in blood donors whose blood group are suspected as cis-AB and B subgroup. METHODS: Genotyping for ABO was performed in peripheral blood DNA samples from eight cis-AB donors and five B subgroup donors at red cross blood center. DNA sequencing was performed on Bint, B3 and two cis-AB samples. RESLUTS: All eight cis-AB donors showed that they have cis-AB allele and C467T substitution. Through DNA sequencing it was confirmed that cis-AB allele was derived from A allele mutation and two B subgroups showed no base sequence difference with B blood group. CONCLUSIONS: The genotyping method would be useful tool to determine blood group variants in blood donors. And more investigation is required for elucidation of genetic structure and gene expression of ABO blood subgroup.

Anesthetic Management of Patient with Cis A2B3 Blood Group: A case report / 대한마취과학회지

The inheritance of ABO blood type group is actually determined by triple allelic gene, A, B and O. Transmission of blood group AB by a single chromosome, instead of by two separate chromosomes, was reported and called cis AB. The anesthesiologists, who meet many cases of the transfusions, may anesthetize cis AB patients for surgery. Recently the authors have experienced one case of patient with cis AB blood type undergoing emergency craniotomy and removal of hematoma. We transfused the patient with Rh+O packed red blood cell without any significant transfusion reactions.

Molecular Genetic Analysis of Cis-AB with Cytosine at nucleotide position 467 / 대한수혈학회지

BACKGROUNDS: The molecular genetic characteristcs of cis-AB blood group have shown that its allele had C, G, C and C at nucleotide positions (nps) 526, 703, 796 and 803, respectively. And all cis-AB analysed and reported molecular genetically in Korea and Japan had T at np 467 (leucine at amino acid position 156). We report a first case of cis-AB with C at np 467 (proline at amino acid position 156). METHODS: Genomic DNA was extracted from peripheral blood of cis-AB patient and amplified by DS1/DS2 and DS3/DS4 allele-specific primers. After PCR, we analysed nps 261, 467, 526, 646, 703, 796, and 803 by restriction digestion, autoradiography and automatic sequencing. RESULTS: PCR-RFLP with DS1/DS2 primers and restriction enzyme KpnI showed that cis-AB had an O allele. The results of genomic sequencing, autoradiography and restriction digestion showed that cis-AB allele at nps 467, 526, 646, 703, 796 and 803 had C, C, T, G, C and C, respectively. CONCLUSION: This cis-AB showed characteristic molecular genetic features at nps 526, 703, 796, and 803. And this is a first case of A(Pro) cis-AB with C at np 467.

Molecular Genetic Analysis of Cis-AB with Cytosine at nucleotide position 467

BACKGROUNDS: The molecular genetic characteristcs of cis-AB blood group have shown that its allele had C, G, C and C at nucleotide positions (nps) 526, 703, 796 and 803, respectively. And all cis-AB analysed and reported molecular genetically in Korea and Japan had T at np 467 (leucine at amino acid position 156). We report a first case of cis-AB with C at np 467 (proline at amino acid position 156). METHODS: Genomic DNA was extracted from peripheral blood of cis-AB patient and amplified by DS1/DS2 and DS3/DS4 allele-specific primers. After PCR, we analysed nps 261, 467, 526, 646, 703, 796, and 803 by restriction digestion, autoradiography and automatic sequencing. RESULTS: PCR-RFLP with DS1/DS2 primers and restriction enzyme KpnI showed that cis-AB had an 0 allele. The results of genomic sequencing, autoradiography and restriction digestion showed that cis-AB allele at nps 467, 526, 646, 703, 796 and 803 had C, C, T, G, C and C, respectively. CONCLUSION: This cis-AB showed characteristic molecular genetic features at nps 526, 703, 796, and 803. And this is a first case of A(Pro) cis-AB with C at np 467. (Korean J Blood Transfusion 10(1): 13-19, 1999)