RESUMEN
BACKGROUND: The infectious mononucleosis (IM) includes clue elements, apoptotic and atypical lymphocytes. In IM, the evaluation of dot plot provided by Sysmex XN-1000 analyzer revealed a stretched lymphocytic cluster, white cell differential channel (WDF), on cytogram. METHODS: In this study, we analyzed 698 samples that include 39 IM, 76 chronic lymphoproliferative disorders, 25 nonclonal lymphocytosis, and 40 healthy donors. Five hundred eighteen samples with other diseases or interference were evaluated. The algorithm was validated on 40,000 files that were received from internal database of Sysmex-Dasit. RESULTS: The analysis of flow cytometry standard (FCS) files in WDF channel and presumed apoptotic lymphocytes counts on side scatter/forward scatter (SSC/FSC) and SSC/SFL (where SFL is side fluorescence) dot plot revealed excellent correlation among apoptotic cells on peripheral blood smear (R(2) = 0.79 and 0.75). There was a variation of positional parameters in lymphocyte clusters WX, WY, and WZ. If WX-SSC > 500 and WY-SFL > 1,000 and WZ-FSC > 700, specificity equals to 99% and sensitivity equals to 100%. If nucleated red blood cell (NRBC) <0.03 × 10(3) /µl, specificity equals to 100%. In received files, positives were 1% adding the simultaneous presence of a percentage of events in the two gates relating to the apoptotic lymphocytes of 1.2% of WBC. CONCLUSION: On Sysmex XN-1000, dot-plot observation allowed immediate detection of IM. Meanwhile, an algorithm based on the parameters on these plots can be calculated with excellent performance.