A new low ionic strength test for assessment of pretransfusion compatibility. Studies in vitro and in vivo.

A new simple low ionic strength antiglobulin test (LIS-AGT) is presented for use in the antibody screening phase of pretransfusion tests. The ionic strength during the incubation phase of LIS-AGT is held between 15-17% of that of indirect AGT, and 8 mM EDTA is added to serum to inhibit false-positive tests. The prevalence of false-positive LIS-AGT was determined to be approximately two times higher than that observed with the indirect AGT. The new test was superior to the indirect AGT in detecting antibodies specific to Rh, Duffy, Kidd, and MNSs antigens, while the indirect AGT was superior in detecting antibodies specific to K and Lewis antigens. On the basis of three 51Cr red blood cell (RBC) survival studies, it was shown that antibodies reactive with LIS-AGT only decreased the long-term survival of incompatible erythrocytes, although the one-hour recovery was not affected. It appeared that antibodies reactive by LIS-AGT only can cause delayed rather than acute hemolytic transfusion reactions. The data shown indicate that the LIS-AGT is a simple and valuable addition to the pre-transfusion antibody screening test.