Should pre-transfusion screening RBC panels contain Wr(a+) cells?

Sometimes commercial RBC sets for the screening of irregular antibodies contain Wr(a+) cells. The aim of this study was to define the usefulness of employing RBC sets for the screening of irregular antibodies containing Wr(a+) cells in pre-transfusion tests. Anti-Wr(a) is a relatively common naturally occurring antibody in candidates to blood transfusion, although the risk of receiving a non-compatible unit is low. We have studied both the incidence of Wr(a) antibodies and the effects of having a Wr(a+) cell in the screening test on routine work in an unselected population of 787 patients requiring RBC transfusion and in 151 new blood donors. Irregular antibodies were found in 64 sera, 58 of which were specific for Wr(a) , 46 (5·8%) and 12 (7·9%) in patients and donors, respectively. The positive tested sera contained specific IgM in 16 cases, IgM + IgG in 13 cases and IgG in 27 cases. Anti-Wr(a) can usually be detected during cross-match procedures; therefore, the presence of Wr(a+) cells in pre-transfusion screening of blood recipients is not justified and it causes an undue increase in cost and time to unit release. Moreover, because of the rare association between anti-Wr(a) and haemolytic transfusion reaction, the use of Wr(a+) RBC-containing sets is also questionable in the countries that do not perform pre-transfusion cross-match tests.