Study of Prevalence of A2, A2B along with major ABO Blood Groups to minimize the transfusion reactions

Research on ABO blood group system has been of immense interest, due to its medical importance in different diseases. The heterogeneity of A and B alleles results in weak variants of these antigens. Subgroups of A differ both quantitatively and qualitatively. The aim of the present study was to study the frequency of A subtypes and to study the prevalence of A2 and A2B along with other major blood groups in the healthy donors in eastern India. Blood samples from 3918 donors were types into major ABO blood groups using standard tube technique. Anti-A1 lectin studies were done for all patients with groups A and AB and they were classified into A1/A1B, A2/A2B. ABO blood groups detected in 3918 blood donors were 37.2% of ‘O’ blood group, 33.6% of ‘B’ blood group, 22.3% of ‘A’ blood group and 6.8% of ‘AB’ blood groups. The A and AB blood groups were subtyped into 88.1% A1 and 11.9% A2, 5.8% A2 blood groups were found in A blood group and 31.5% A2B were found in AB blood group. The result of our study show a significantly higher proportion of A2B subtypes than A2 subgroups. Patients should receive these compatible blood groups to minimise the reactions occurring due to blood transfusion. INTRODUCTION: ABO system remains the most important blood group system in transfusion and organ transplant medicine.1It was initially discovered by Karl Landsteiner in 1900 On the basis of presence or absence of A or B antigen on RBC2. Later De Casterllo & Struli discovered the fourth blood type (AB) in 1902.3Rh blood group, referred as Rhesus blood group, is the second important group in Transfusion Medicine. It was recognised in 1939 which was confirmed within few years. This system is highly polymorphic due to the presence or absence of Rh (D) antigen on red cells. ABO subgroups are phenotypes which differ in amount of A and B antigens present on red cells and secretions. ‘A’ subgroup is more common than ‘B’ subgroup. Clinically the most common subgroups encountered are A1 and A2 constituting 80% and 20% respectively. Extremely weak A (and) B subgroups are infrequently encountered which can be recognized by the apparent discrepancies between red cell ( forward) and serum (reverse) grouping results. The distinction between A1 and A2 subgroups can be made by observing reactivity with the lectin from Dolichos biflorus seeds. The Dolichos biflorus lectin reacts specifically with the cells of A1 subgroup and agglutinate A1, but not the A2 cells. A2 phenotype reflect the inefficient conversion of H → A antigen, A2 red cells show increased reactivity with Anti-H lectin Ulex eruopaeus. Extremely weak A (and B) subgroups are infrequently encountered which can be recognized by the apparent discrepancies between red cell ( forward) and serum (reverse) grouping results. 4In weak sub-groups of A, erythrocytes give weaker reactions or are non-reactive serologically with antiA antisera than the subjects with A2 red blood cells. In the present study, we have first determined ‘A’subgroup dissecting out A2 and A2B groups along with other major ABO subgroups in the healthy donors. MATERIAL & METHODS: From April to June 2015, blood samples from 3918 donors were typed & ABO blood group ‘A’, ‘B’, ‘AB’, ‘O’ were found in 873(22.2%), 1318(33.6%), 269(6.8%), 1458(37.2%) of donors respectively. Blood grouping was done by test tube technique. Forward grouping was done using monoclonal antisera anti-A, anti-B, anti-AB, & anti-D (Tulip Diagnostic, Goa, India) & reverse grouping by in-house prepared pooled A cell, B cell, & O cell. Blood groups were interpreted based on agglutination pattern in both forward grouping and reverse grouping. In forward grouping, A or B antigen agglutination was observed with the corresponding antisera & circulating anti-A or anti-B were detected by reverse typing using pooled cells. The blood samples were classified as Rh-D positive or Rh-D negative according to the presence or absence of the antigen D. For forward grouping, 1 ml of whole blood was washed thrice with saline, each time followed by centrifugation for five minutes. Finally 3% red cell suspension was prepared by transferring 0.3 ml of washed red cells to a test tube with 9.7 ml of saline. 1 drop of anti-A, anti-B & anti-AB were placed in labelled tubes. To each test tubes 1 drop of 3% suspension of the red cells were added. After mixing, centrifugation, red cell buttons were resuspended & examine for agglutination. For reverse grouping, two drops of serum 1 drop of A1, B, A2 reagent cells are added to the labelled test tubes. After mixing, centrifugation, the serum was examined for agglutination. Agglutination was graded according to AABB guidelines. One solid agglutinate was graded 4+, several large agglutinates as 3+, medium size agglutinates with clear background as 2+ and small agglutinates with a turbid background as 1+, very small agglutinates with a turbid background were graded as weak reaction (wk) and mixtures of agglutinated and un-agglutinated red blood cells as mixed field (mf). 5Samples of group A and AB were further tested with anti-A1 lectin (Tulip Diagnostic,Goa,India) to classify them into A1, A2 subgroups. When the sample showed 4+ agglutinates with anti-A antisera but negative anti-A1 lectin, the sample was considered as A2 subgroup. A or AB blood group samples showing agglutination with pooled A cells were tested with A1 cells to confirm presence of anti-A1 antibodies. RESULTS: ABO Blood groups detected in 3918 blood donors were 1458 of