On a much higher than reported incidence of anti-c in R₁R₁ patients with anti-E

A previous study involving tube IATs, untreated RBCs, and a low-ionic-strength additive reagent revealed that approximately one-third of R₁R₁ patients with anti-E have a concomitant anti-c. However, the current study finds a much higher incidence of anti-c in such patients, using gel technology in conjunction with ficin-pretreated RBCs. Results of antibody identification studies and transfusion records of 82 R₁R₁ patients with anti-E were reviewed. Serologic test methods included a LISS wash solution for tube IATs (15 min at 37°C, anti-IgG), ficin-tube IATs (30 min at 37°C, anti-IgG + anti-C3), and gel IATs (untreated or ficin-treated RBCs or both, anti-IgG gels). LISS-tube or gel IATs with untreated RBCs revealed anti-c in 32 patients with anti-E. When gel-IAT and ficin-pretreated RBCs were used, 21 additional patients with anti-E were found to have anti-c. In samples from 26 R₁R₁ patients with anti-E, anti-c was not demonstrable by ficin-gel IATs, and in 3 cases, the ficin-gel tests were inconclusive. In five cases in which E– RBCs not tested for c antigen were transfused to patients found by ficin-gel IAT to be without anti-c, all subsequently performed crossmatches with E–, c-untested RBCs were compatible. The incidence of anti-c in R₁R₁ patients with anti-E in this study was 32 of 82 (39%) with untreated RBCs and 53 of 82 (65%) when the ficin gel data were included. The latter is significantly higher than the 32 percent incidence previously reported (p = 0.0001). Accordingly, all patients at our facility with an Rh antibody are now tested for those additional Rh antibodies they can make, as predicted from their Rh phenotype. The data from this study strongly support the selection of R₁R₁ RBCs for all c– patients with anti-E. Immunohematology2005;21:94–96.