A simple method for inhibiting ABO antibodies in sera used for platelet crossmatching

Sometimes it is necessary to crossmatch and transfuse ABO-incompatible platelets. As IgG anti-A and anti-B sometimes react with platelets from group A or B donors, these reactions can confuse the interpretation of crossmatching, which is designed to detect HLA or platelet-specific antibodies. Methods previously described to overcome this problem have been complex. Neutr-AB^R, which contains A and B blood group substances from porcine and equine sources, can be used to neutralize anti-A and/or anti-B in sera used to crossmatch ABO-incompatible platelets. This simple technique has been used for many years in red blood cell (RBC) serology and involves simply adding 1 volume of Neutr-AB to 5 volumes of serum and incubating at room temperature for 5 minutes. In this study, 13 of 65 (20%) random group O donor sera reacted against random group A platelets and 6 of 67 (9%) random group O donor sera reacted against random group B platelets. All of the anti-A and anti-B reactions were inhibited by Neutr-AB when tested against group A or B platelets by solid-phase ELISA. The amount of A antigen on platelets and the levels of anti-A in group B or O sera can vary considerably, so we investigated the extent of the problem in platelet crossmatching. Sixty percent of 20 random group O sera reacted with platelets from a donor, who was selected because of the strong A antigen present on the platelets. Eighty-six percent of randomly selected group A platelets reacted with a group O serum containing strong anti-A. Neutr-AB was found not to inhibit 1 anti-P1^A1 and 6 anti-HLA.