P05 Distribution and Significance of High Titre Anti A and Anti B in a UK Blood Donor Population

Abstract

A risk of clinically significant haemolysis exists where high titre (HT) anti A and anti B in blood components, particularly platelets, are transfused to patents with the corresponding antigen. Risk is reduced by screening all donations and designating packs with an anti A or B titre of over 1:128 as HT positive. This study reports on agglutination titres, haemolysin levels and the sex of donors. The Olympus PK7200 is used for automated screening of donors; 20 HT positive, 20 HT query and 20 negative group O donations were selected. Agglutination titres against A1 and B cells were determined manually by incubating one drop of doubling dilution of donor plasma from neat to 1 : 512 at room temperature for two hours with one drop of cells. All samples were manually tested for the presence of haemolyisns; one drop of washed A1 or B cells and four drops of neat donor serum were incubated at 37 0C for 5 min, centrifuged and visually inspected for haemolysis. In addition, the sex of the donor was noted from session records. All HT samples had a manual titre between 1 : 128 and 1 : 512, with levels of agglutination between one and five. The HT query samples showed agglutination below 1:128 and the HT negative samples showed agglutination below 1 : 32. Haemolysin testing showed hemolytic activity in 16/20 HT positive samples, 4/20 HT query and 1/20 HT negative. Of the HT positive donors 18/20 were female, as were 13/20 HT query and 11/20 HT negative. The results of the manual titres suggest the Olympus PK7200 is accurate in detecting HT positive and query donations. The results of the haemolysin investigation show good correlation with HT testing results. Findings of gender analysis support a theory of female donors having more HT antibodies, possibly as a result of previous stimulating events. Guidelines for ‘out of group transfusion’ and associated donor testing varies internationally. An important consideration is balancing the risk of transfusion reaction against the risk of limited availability of group matched products. Reports of haemolytic reactions are uncommon but SHOT reports repeatedly demonstrate ongoing cause for concern.