FlowDiff: a simple, flow cytometry-based approach for performing a leukocyte differential count.

To overcome the challenges of a manual leukocyte differential count, we have developed FlowDiff, an 8-colour, single tube flow cytometry panel, and investigated whether it could potentially replace the manual differential in our laboratory. The instrument was set up in accordance with the EuroFlow settings, and the protocol comprised a stain-lyse no wash process, taking approximately 30 min of working time, without the addition of a toxic lysis reagent. We found a very good correlation for all leukocyte populations between FlowDiff and the Sysmex XN analyzer in 80 normal, non-flagged samples. In addition, FlowDiff showed a very good correlation with manual differential in 168 abnormal samples, as well as a high diagnostic accuracy. FlowDiff correctly identified all samples with acute leukemia (N = 13) and differentiated all B-lymphomas (N = 49) in samples with lymphocytosis. Moreover, FlowDiff detected an additional five samples with B-lymphocytosis without any prior hematological malignancy, which turned out to be a B-lymphoma. Our data suggest that FlowDiff, our 8-colour flow cytometry-based differential, is comparable to, and can successfully substitute the manual differential.