Decreased sensitivity of the automatic white precursor cell channel (WPC) for blast flagging in patients with leukopenia

• For patients with leukopenia, white cell precursor channel (WPC) for blast flagging showed decreased sensitivity.
• The correlation of white cell differential (WDF) mode with WPC was low in leukopenia group compared to normal WBC group.
• Most of the missed blasts after running WPC mode were under chemotherapy or hematopoietic stem cell transplantation.

ObjectivesThe advantage of Sysmex XN system is its performance of an automatic reflex test in white cell precursor (WPC) channel, which gives an accurate differential count. We performed a real-time evaluation of the automatic differential count according to WBC number with Sysmex XN series and demonstrated a significant differential impact on blast distinction depending on the number of WBC.Design and methodsWe categorized the 49,699 specimen according to WBC number and compared the results of blast flagging in the white cell differential (WDF) channel and WPC channel on the basis of the results of manual differential count. Additionally, clinical impact of missed blasts after running WPC reflex test was analyzed.ResultsFor patients with WBC under 1.5 × 109/L, blast flagging for WPC channel showed markedly decreased sensitivity (56%) compared to that of WDF mode (100%). Most of the patients with missed blasts in WPC mode were under chemotherapy or hematopoietic stem cell transplantation. The specificity and efficiency for WPC channel were much higher than that of WDF mode in all range of WBC.ConclusionsConsidering the additional reagent cost required for the WPC channel, WPC reflex test is not suitable for patients with leukopenia if it is operated alone. Instead, manual blood film review or double-check with other supplemental equipment should be accompanied.