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 Table of Contents  
Year : 2021  |  Volume : 8  |  Issue : 2  |  Page : 87-89

Detection of rare blood group Ax phenotype in blood donor

Department of Blood Bank, Regency Hospital Ltd., Kanpur, Uttar Pradesh, India

Date of Submission31-May-2021
Date of Decision04-Oct-2021
Date of Acceptance16-Oct-2021
Date of Web Publication30-Dec-2021

Correspondence Address:
Dr. P. M. Bala Bhasker
Department of Blood Bank, Regency Hospital Ltd., Kanpur, Uttar Pradesh
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijamr.ijamr_121_21

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Background: Karl Landsteiner discovered ABO blood group system in early 20th century, but still, uncertainty remains in immune-hematology while detection of ABO subgroups or weaker variants. The presence of weak subgroups in blood donor samples gives rises to discrepancy in forward (cell) and reverse (serum) grouping. Methods and Materials: We here report a case of the 'A' weak Rh 'D' Positive, Probably Ax Phenotype in a blood donor who came for replacement donation at our blood bank. The blood group discrepancy was resolved by using serological testing, Adsorption elution technique and saliva secretor study. Results: Blood grouping by the tube technique showed no reaction was shown with anti-B, a faint reaction with anti-A, 1+ agglutination with Anti-AB, and a significant reaction (4+) with anti-D and anti-H. The patient's serum showed the presence of anti-B antibody as well as anti-A1. Result for eluate showed microscopic agglutination (1+) with group A cells and a negative reaction with group B cells and saliva secretor study showed having only H substance. Conclusion: This report highlights the importance of cell and serum grouping in solving blood group discrepancy in blood donors. This rare phenotype in a donor is first of its kind reported from India.

Keywords: Ax phenotype, blood donor, rare blood group

How to cite this article:
Kumar R, Bhasker PM, Jain R, Chandra A. Detection of rare blood group Ax phenotype in blood donor. Int J Adv Med Health Res 2021;8:87-9

How to cite this URL:
Kumar R, Bhasker PM, Jain R, Chandra A. Detection of rare blood group Ax phenotype in blood donor. Int J Adv Med Health Res [serial online] 2021 [cited 2023 Mar 25];8:87-9. Available from: https://www.ijamhrjournal.org/text.asp?2021/8/2/87/334363

  Introduction Top

Karl Landsteiner discovered the ABO blood group system in the early 20th century, but still, uncertainty remains in immune hematology while detection of ABO subgroups or weaker variants. A disparity in forward (cell) and reverse (serum) grouping is caused by the presence of weak subgroups in donors. The ABO blood type antigens are produced by combining a precursor oligosaccharide H chain with a terminal monosaccharide immunodominant sugar.[1] A, B, and H antigen expression on the red cell surface is frequently hereditary or acquired. They are probably the tiniest amount that is commonly encountered, and they are a challenge in everyday immune-hematology practice.[2] Antigenic alterations in hematological malignancies are most commonly associated with the ABO blood type system.[3] The strength of agglutination with anti-A, anti-B, anti-AB, and anti-H serum, the presence or absence of ABO isoagglutinin in the serum, saliva secretor tests, and adsorption-elution investigations, as well as pedigree analysis, can all be used to identify the weaker variations of the A group. A3, Aend, Ax, Am, Ay, and Ael are all possible weak subgroups of A. We report an incidentally detected case of Ax blood type in a 43-year-old male blood donor.

  Case Report Top

A 43-year-old donor came to the blood bank, affiliated with the department of transfusion medicine in a tertiary care hospital of Central India. The blood donor belonging to the northern plains of India with Indo-Aryan ethnicity came for blood donation as a replacement donor. His hemoglobin was 14 g/dl and his weight was 75 kg. The donor was screened for whole blood donation as per the Drugs and Cosmetics Act, Government of India. After a thorough history and medical examination, the donor was selected for whole blood donation and 350 ml whole blood was collected.

Donor routine blood grouping was performed in a fully automated immune hematology analyzer (Matrix AutoMax-80, Tulip Diagnostics (P) Ltd, India) by cell and serum grouping on gel column agglutination technology. For cell grouping, the three microtubes used contain monoclonal anti-A, anti-B, and anti-D antisera in each well and for serum grouping, the three other microtubes used contain pooled A, B, and O cells in each well. Blood group discrepancy was observed in cell and serum grouping [Figure 1]. The donor's red cells were nonreactive with anti-A and anti-B, with 4+ agglutination with anti-D in cell grouping, whereas in serum grouping, 4+ agglutination was found in microtube containing B pooled cells with no agglutination in microtube containing O and A pooled cells.

When blood grouping was done again using the traditional tube method (CTT: Conventional Tube Technique), no reaction was shown with anti-B, a faint reaction with anti-A, 1+ agglutination with anti-AB, and a significant reaction (4+) with anti-D and anti-H. The patient's serum showed the presence of anti-B antibody as well as anti-A1 [Table 1]. The blood-grouping pattern shows a Type II blood group discrepancy, probably a weaker subgroup of A.
Figure 1: Findings of donor grouping on Matrix AutoMax-80

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Table 1: Serological reactions of Ax weak subtype (Tube technique)

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To detect the presence of weak A antigen, an adsorption–elution test was performed. The donor's red cells were incubated with Group O serum for adsorption and heat elution of the adsorbed cells was performed after washing three times using normal saline. The eluate showed microscopic agglutination (1+) with Group A cells and a negative reaction with Group B cells. To detect the presence of soluble substances, secretor status was decided using the donor's saliva. The donor was found to be a secretor, having only H substance detectable within the saliva. These serological findings noticed suggest the reactivity pattern of the Ax subtype.

  Discussion Top

The ABO gene is situated on chromosome 9 and is made up of seven exons, with exons 6 and 7 containing the majority of the coding sequences. Exon7 amino acid changes control whether the glycosyltransferase will generate A antigens using UDP-N-acetyl-d-galactosamine (A transferase) donor sugars.[4],[5] The A1 and A2 phenotypes account for 99% of all A individuals. Both qualitative and quantitative differences are seen in A1 and A2 antigens. A1 individual carries 8.1–11.7 × 105 antigenic sites on the RBC, while A2 individual RBC carries only 2.9 × 105 antigenic sites. About 1%–8% of A2 and 22%–35% of A2B individuals produce Anti-A1 antibodies in their serum.[6] Anti-A1 antibody is seen almost always in the serum of Ax individuals and seen occasionally in A3, Aend, and Ael individuals.[2]

A study by Thakral et al. shows that among the weaker subgroups of A, A3 and Ax have a similar frequency of approximately 1:14,448 and Aend frequency is 1:43,344 in the Indian blood donor population.[7] The most common Ax allele has the A1 consensus sequence with a missense mutation encoding a Phe216Ile substitution.[8] In the majority of instances, mutations in exons 6 and 7 (which make up 77% of the ABO gene) have been investigated for allelism.[9] The inheritance and expression of variant alleles at the ABO locus result in weaker versions of A.[7] For the differentiation of weak subgroups, further special procedures such as molecular testing for mutations or serum glycosyltransferase investigations for detecting the A enzyme can be conducted.[4],[7],[10]

They are mostly identified using hemagglutination-based methods. However, these weaker phenotypes are often mistyped as O group due to variation in reagents and techniques used.[11] Most of the laboratories in the remote areas still report blood grouping by performing only cell grouping by slide method, where the weaker antigens usually are not detected and as a result, the donors are typed wrongly.

If a red blood cell component of the weaker subgroup is mistyped and labeled as O group and transfused to an O group recipient, it will result in hemolysis within the recipient's serum due to the presence of ABO antibodies. Management of “O” group RBCs and “AB” plasma for transfusion in discrepant cases will be done appropriately only after the accurate determination of the ABO type.[11] The donor was given information on his rare blood group, as well as a full immunohematology report that included his blood group (“A” weak Rh “D” positive, most likely Ax phenotypic) and the results of other tests like adsorption-elution and saliva secretor study undertaken to determine his blood group. A rare blood donor card was also given and the donor was advised not to donate blood in the future to avoid mistyping and to avoid ABO-incompatible transfusion to O group recipient. It was also mentioned as a transfusion recipient, he should receive only O group PRBC: Packed Red Blood Cell in the future.


Our case report is limited by the fact that molecular testing for mutations and serum glycosyltransferase studies of the donor was not done because of the unavailability of the facility at our center.

  Conclusion Top

The ABO blood group system's weak subgroups are rarely reported in ordinary activities. Advanced procedures such as adsorption–elution, saliva secretor studies, and molecular testing are used to resolve ABO inconsistencies. These units may be incorrectly classed as O due to identification errors, and if transfused to O group patients, may result in lower red cell survival due to naturally occurring anti-A antibodies in the recipient, which, if clinically substantial, can result in lethal transfusion reactions.

  Declaration of patient consent Top

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Storry JR, Olsson ML. The ABO blood group system revisited: A review and update. Immunohematology 2009;25:48-59.  Back to cited text no. 1
Harmening DM. The ABO blood group system. In: Modern Blood Banking and Transfusion Practices. 7th ed. Philadelphia: FA Davis Company Publications; 2019. p. 119-45.  Back to cited text no. 2
Winters JL, Howard DS. Red blood cell antigen changes in malignancy: Case report and review. Immunohematology 2001;17:1-9.  Back to cited text no. 3
Seltsam A, Blasczyk R. Missense mutations outside the catalytic domain of the ABO glycosyl transferase can cause weak blood group A and B phenotypes. Transfusion 2005;45:1663-9.  Back to cited text no. 4
Watkins WM. Genetics and biochemistry of some human blood groups. Proc R Soc Lond B 1978;202:31-53.  Back to cited text no. 5
Klein HG, Anstee DJ. Mollison's Blood Transfusion in Clinical Medicine. 12th ed. Somerset (NJ): Wiley-Blackwell Publishing; 2014.  Back to cited text no. 6
Thakral B, Saluja K, Bajpai M, Sharma RR, Marwaha N. Importance of weak ABO subgroups. Lab Med 2005;36:32-4.  Back to cited text no. 7
Olsson ML, Irshaid NM, Hosseini-Maaf B, Hellberg A, Moulds MK, Sareneva H, et al. Genomic analysis of clinical samples with serologic ABO blood grouping discrepancies: Identification of 15 novel A and B subgroup alleles. Blood 2001;98:1585-93.  Back to cited text no. 8
Yamamoto F. Molecular genetics of ABO. Vox Sang 2000;78 Suppl 2:91-103.  Back to cited text no. 9
Mizuno N, Ohmori T, Sekiguchi K, Kato T, Fujii T, Fujii K, et al. Alleles responsible for ABO phenotype-genotype discrepancy and alleles in individuals with a weak expression of A or B antigens. J Forensic Sci 2004;49:21-8.  Back to cited text no. 10
Kulkarni S, Gogri H. Molecular concepts in immunohematology. In: Choudhury N, editor. A Textbook on Laboratory and Clinical Transfusion Medicine: Basics of Blood Bank Practices (Process control). Vol. 2. New York: Nova Science Publishers, Inc.; 2017.  Back to cited text no. 11


  [Figure 1]

  [Table 1]


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