Red blood cell diluent composition is important for detection of some anti-E

Commercially prepared 0.8% reagent red blood cells (RBCs) eliminate the need to manually dilute 3 to 5% RBCs for use in gel cards. Ortho-Clinical Diagnostics investigated twelve anti-E samples detected in MTS Anti-IgG gel cards using Ortho 3% reagent RBCs manually diluted to 0.8% in MTS Diluent 2™ (MTS2) that were not detected with commercially prepared Ortho 0.8% reagent RBCs. In gel tests, using additional examples of E-positive RBCs, 22 of 26 anti-E were reactive when the cells were suspended in MTS2. Only 6 of 28 anti-E were reactive with E-positive Ortho 0.8% reagent RBCs. Five anti-E were tested in gel with five R₂ R₂ RBCs that had been washed and resuspended in four low-ionic-strength diluents. Fiftyeight percent of tests performed in MTS2 were positive compared to 13 to 41 percent for the other diluents. Anti-E detection also varied from 6 to 56 percent based on the donor of the RBCs. Seven anti-E were characterized by their reactvity in tube techniques and were reactive using PEG and/or ficin-treated RBCs only. As a comparison, 25 archived examples of anti-E were detected using RBCs suspended in MTS2 and Ortho 0.8% reagent RBCs. These data show that some anti-E are not detected by Ortho reagent RBCs in MTS Anti-IgG gel cards. However, these anti-E have characteristics of antibodies of questionable clinical significance. Immunohematology 2000; 16:142–146.