A flow cytometry method, developed in our laboratory to measure red cell (RBC)-bound IgG, was compared to the manual titration technique in the measurement of RBC antigen strength to determine zygosity. Parallel studies using antibodies to antigens in the Rh, Kell, Kidd, Ss, and Duffy systems were performed. The antisera (n = 20) were tested against five examples each of RBCs from apparent homozygotes and heterozygotes. The flow cytometry method was clearly superior, showing distinct differences, with no overlap of the ranges of results, between the reactions of RBCs from homozygotes and heterozygotes with 10 of 20 (50%) antisera. By the manual titration technique none of these sera clearly demonstrated dosage and 15 showed overlap of the ranges. It was obvious from the results that the commonly used manual titration technique for comparing the test RBCs with a single example of RBCs from a homozygote and heterozygote yielded inaccurate results.
An example of an unusual cold autoagglutinin is reported. The antibody was monoclonal IgMKappa able to fix complement, and, in the presence of albumin, had both a high titer (greater than 4,096 at 4 degrees C) and a wide thermal range (4-37 degrees C). The patient was closely followed over a 3-year period with no evidence of hemolysis ever documented, despite a persistently positive direct antiglobulin test and the presence of the cold autoagglutinin. In contrast to previous reports regarding cold-agglutinin disease, this case demonstrates that in vivo hemolysis is not always associated with cold autoagglutinins that in vitro show a high thermal range in the presence of albumin.
An example of an unusual cold autoagglutinin is reported. The antibody was monoclonal IgMKappa able
to fix complement, and, in the presence of albumin, had both a high titer (>4,096 at 4°C) and a wide thermal range
(4-37°C). The patient was closely followed over a 3-year period with no evidence of hemolysis ever documented,
despite a persistently positive direct antiglobulin test and the presence of the cold autoagglutinin. In contrast to
previous reports regarding cold-agglutinin disease, this case demonstrates that in vivo hemolysis is not always
associated with cold autoagglutinins that in vitro show a high thermal range in the presence of albumin.
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