The integration of Sysmex XN‐9100’ WPC channel reflex testing in the detection of reactive versus malignant blood samples

Abstract Introduction Sysmex XN‐9100 ™ (Sysmex, Kobe, Japan) system has an optional White Progenitor Cell (WPC) channel. While the White Differentiation (WDF) channel reports a combined flag for blasts/abnormal lymphocytes, WPC channel specifies flagging into a separate flag for each cell type or removes the flag entirely. Aim of this study was to evaluate the added value of this WPC channel in the detection of malignant samples. Methods Routine blood samples analyzed on Sysmex XE‐5000 with flagging for either blasts, abnormal lymphocytes, or atypical lymphocytes (n = 630) were selected for testing on Sysmex XN‐9100, resulting in a reflex WPC analysis in 420 samples. All samples were microscopically evaluated with DI‐60 digital cell imaging analyzer. Results WPC reflex testing resulted in a suspect flag ("blasts" and/or "abnormal lymphocytes") in 334 samples, which was confirmed microscopically in 38% (128/334). In all true positive samples, WPC correctly classified the initial WDF flag in either "blasts" flag or "abnormal lymphocytes?" flag in 75%. Only 12% (50/420) of WDF "blasts/abnormal lymphocytes" positive samples became negative after WPC reflex testing. Subgroup analysis showed differences between the "pediatric" versus "adult" groups and the "hematological/chemotherapy" versus "nonhematological/nonchemotherapy" groups in specificity and smear reduction. Conclusion Overall, WPC reflex testing showed good sensitivity (99%); however, the specificity remains poor (29%). Using reflex WPC to the WDF channel resulted in a 12% reduction of the smear review rate. Although the WPC channel offers different interesting advantages, additional topics and a specific workflow should be applied to optimize the use of this channel.