Anti-A and anti-B haemolysins are lytic antibodies that cause haemolysis of red blood cells of recipients when ‘O’ group blood or plasma is transfused to non ‘O’ group patients. They are known to cross the placenta and cause haemolytic disease of the newborn. These antibodies are large fractions of A and B antibodies that belong to IgG and IgM class of antibodies. Most blood group O individuals that are over the age of 6 months possessed anti-A and/or anti-B in their serum if they lack the corresponding A or B antigens on their red cells. These antibodies may become clinically significant high titre immune antibodies. The occurrences of anti-A (alpha haemolysin) and anti-B (beta haemolysin) in group O donors have been reported to be high in African population. The prevalence of haemolysins among group O donors in Federal Teaching Hospital, Abakaliki was determined using haemolysin assay and antibody titration. Data obtained were analyzed statistically using descriptive statistics and inferential statistics of Chi-Square. One hundred and fifty seven samples from group O donors comprising 126 (80.25%) males and 31 (19.75%) females were enrolled for this study. Among the overall population studied, a total of 83 (52.87%) had alpha and/or beta haemolysin. Alpha haemolysin was found in 33 (39.76%), 26 (31.33%) had beta haemolysin while 24 (28.91%) had both alpha and beta haemolysin. Among the 83 samples positive for haemolysins, 52 (62.65%) had significant titre (visual titre of 8 and above) while a total of 53 (63.85%) had visual titre. This study advocates the need to routinely screen for haemolysin whenever a group O donor blood is to be transfused to a non-group O recipient. 

Keywords: Haemolysin; Donors; Blood group O; Titre; Heamolysin assay