T-cells as cell size calibrators of B leukaemic cells in flow cytometry

In this retrospective study, we reviewed our list-mode recorded data of flow cytometry analayses of lymphocytes from patients with CD5+ B leukaemia to evaluate the feasibility of cell size analysis as a diagnostic complementto the determination of the fluorescent cell surface markers. We estimatedthe cell size of CDS-positive B leukaemic cells by reference to the normalCDS-positive T cells. Typically, a B/T size ratio below 1 (small cell) wasencountered in true chronic lymphocytic leukaemias (CLL, Group 1), and higher values were frequently found in CLL with prolymphocytic features and leukaemic lymphomas (Group 2), or in chronic B leukaemias with atypical patterns of surface fluorescence or atypical clinical presentation (Group 3). The B/T size ratio was measured as 1.07 +/- 0.17 (means +/- SD) in Group 2, and was significantly different from Group 1 (0.88 +/- 0.06, P < 0.001) and Group 3 (0.94 +/- 0.11, P < 0.05). B cell size estimation is a useful by-product of fluorescence flow cytometry in the classification of CD5-positive chronic leukaemias. A high BIT ratio argues against the diagnosis of classical CLL. On the other side, because of wide overlaps, a low B/T ratio is anunspecific finding. Med Sci Res 27:273-275 (C) 1999 Lippincott Williams & Wilkins.