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Background: The first monoclonal anti-k (anti-KEL2) reagent of the IgM-class (clone: LK1) for the tube spin method is now commercially available. As this reagent is directly agglutinating in contrast to conventional polyclonal anti-k reagents requiring an indirect antiglobulin test, we studied the reaction characteristics of this new reagent carefully before starting its use in our routine blood grouping laboratory.
Methods: The titer of the monoclonal anti-k reagent (manufacturer: Biotest, D-63303 Dreieich) was compared with that of two polyclonal anti-k reagents. The avidity was tested with 2 K+k+ red blood cells (RBCs). The reactivity was examined by 10 K+k+ and 3 K-k+ blood samples. Specificity was tested with 12 k- RBCs from several antibody identification panels and from well known blood donors. The influence of a positive direct antiglobulin test was examined by using antibody-loaded RBCs.
Results: The titer of the monoclonal reagent was the same as that of one of the polyclonal reagents and one geometrical titer step lower than that of the other. At immediate spin and after 5, 10 and 15 minutes incubation at room temperature the reactions of the monoclonal reagent were clear. All 10 K+k+ and all 3 K-k+ blood samples were detected. No false positive reactions were found with RBCs carrying the most important antigens of the ABO, Lewis, P, Rhesus, Kell, Duffy, Kidd, Lutheran, Colton, and Cartwright system. After loading k- D+ RBCs with an incomplete anti-D no false positive reactions were seen. Loading K-k+ RBCs with incomplete anti-k also had no significant influence on the reaction.
Conclusions: Several general advantages of monoclonal reagents of the IgM-class were seen in the new monoclonal anti-k as well: direct agglutination without an indirect antiglobulin test; rapid and simple performance; use in a saline milieu also allowing the examination of RBCs with a positive direct antiglobulin test; lack of false positive reactions caused by contaminating antibodies in the reagent. As in Germany two different reagents must be used for testing a RBC antigen, a further anti-k reagent with a different monoclonal antibody of the IgM-class would be a useful addition.
DOI: Clin. Lab. 2010;56:385-389
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