Abstract
This is case report of a female with “A” sub type with acquired B antigen and non-secretor status, first ever reported with this combination in Nepal, during blood grouping of a sample of a patient with urinary tract infection. The patient was referred to our center for blood grouping, cross matching and transfusion due to severe anemia.
 During routine blood grouping, the red cells showed mixed field agglutination with anti-A, anti- AB and microscopic agglutination with anti-B. On serum grouping, we detected potent Anti-B and no agglutination with anti-A. There was no reaction with anti-A both at room temperature and at 37°C. Her cells were further tested with A1 Lectin and Anti-H antisera. There was strong reaction with A1 Lectin and 3+ macroscopic reaction with anti-H in addition to a positive auto-control. Her direct antiglobulin test was only +1 positive. For her “B” antigen, we acidified B antisera with HCl, which did not give any macro or microscopic agglutination with patient’s red cells. Her “Rh” status was positive and on examining the saliva, she was found to be non-secretor.
 The first choice of blood group for transfusion in this case is the “A1” sub type followed by “O” blood group. As the patient had already received “A” blood group and in the presence of auto antibodies, “A subgroup” blood transfusion should be avoided in her.
Highlights
IntroductionThe ABO blood group system was the first to be discovered and till remains the most important in transfusion practice
The ABO blood group system was the first to be discovered and till remains the most important in transfusion practice. This is due to regular occurrence of Anti-A, anti-B & anti-AB antibodies, reactive at 37°C, capable of causing red cell destruction in persons whose red cells lack the corresponding antigens
A3 is a rare phenotype of blood usually due to allelic difference at “A” locus especially at 7th exon[2]. Many of these subgroups can be wrongly typed as ‘O’ because the “A” antigen is very weakly present on red cell membrane, which cannot be detected if weak anti-A is used in cell typing[3]
Summary
The ABO blood group system was the first to be discovered and till remains the most important in transfusion practice. Because the terminal sugar of the “B” antigen is galactose, anti-B antisera will cross react with the B-like D-galactosamine antigen[8] As this phenomenon is in vivo, only group “A” people can develop an acquired B-like antigen. The condition is transient and disappears when the infection is cured and do not pose any transfusion risks except creating discrepancy in ABO grouping These acquired B antigens are not secreted in saliva and this investigation is useful in differentiating it with rare B subgroups. Anti-B antisera react with the bacterial antigens which have attached to the red cells In vitro, both group O and group “A” cells can acquire the B-like antigen. As this patient had auto antibodies and “A1” blood group was available so her blood was cross matched with A1 positive blood group and she was transfused with this group without any transfusion reactions
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