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