Dear Clinical Flowers: I have a perplexing clinical flow question. We are using BD's MultiTEST with TruCount tubes - a single platform assay--for lymphocyte immunophenotyping and absolute counts. BD has validated this assay with EDTA (a lyophilized anticoagulant) whole blood. We did a comparison of EDTA and ACD, and found that the ACD samples had much better stability at 48 and 72 h. Most of the samples coming to my lab will be shipped from investigative sites, so stability is an issue. The problem is that ACD is a liquid anticoagulant (1 mL ACD and 6 mL blood) so my sample is diluted about 17% (if the tube is completely filled). When I compared the absolute counts from whole blood collected in EDTA and ACD tubes from 10 healthy volunteers, the difference was indeed 17%. So my question is, when I calculate the absolute cell counts, should I correct the cell count by 17% correction factor? The problem is that the tubes are not always filled to capacity. Any thoughts on this dilemma? I get the idea from "the literature" that a lot of folks prefer ACD for flow and are using single platform assays, but I haven't seen a single paper where this question is addressed. I'd appreciate your comments or suggestions. Virginia
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