AbstractIntroductionThe aim of the present study was to evaluate the diagnostic ability of blast flags generated by Sysmex instruments (XE/XN) by comparing with immunophenotyping by flow cytometry (IFCM). Additionally, the ability of manual microscopy and CellaVision DM96 (pre‐ and reclassification) to predict the presence of “true” blasts was investigated.MethodsBlood samples (n = 240) with suspect pathology flags reported by the XE were collected from the daily workload and examined by the XN, by manual microscopy, by CellaVision DM96 and by IFCM (CytoDiff Panel).ResultsThe ROC analysis for blasts showed an area under the curve of 0.64 (“Blasts?”) (XE), 0.57 (“Blasts/Abn Lympho?”) (XN), 0.75 (CellaVision preclassification procedure), 0.78 (CellaVision reclassification procedure), and 0.81 (manual microscopy). The sensitivity of blast detection varied between the methods from 0.41 (XE) to 0.90 (XN), and the specificity varied from 0.17 (XN) to 0.95 (CellaVision reclassification).ConclusionsThe CellaVision reclassification procedure has a diagnostic ability for predicting blasts close to that of manual microscopy. The blood smear methods show a notable number of false negative results. The Sysmex XN reported a higher rate of true positive blast flags than the XE. Taken together, the CytoDiff method could be a useful alternative to smear examination to correctly identify blasts.