Diagnosis of acute myeloid leukemia and system Coulter VCS.

BACKGROUND

The aim of this study was to evaluate the possible contribution VCS could make in a hematological laboratory for the diagnosis of acute myeloid leukemia (AML).

MATERIALS AND METHODS

Peripheral blood samples from 42 AML patients and 58 normal donors were analyzed by flow cytometry with the VCS. Normal and leukemic peripheral blood samples were tested to establish a correlation between VCS data and the reference manual method. We evaluated the sensitivity threshold of the VCS for blast cell detection in progressively diluted samples. We looked at a correlation between different scatterplots and flags and the FAB classification of acute myeloid leukemia in order to identify a characteristic VCS image for each subtype. Thirty-four bone marrow samples (18 normal donors and 16 leukemic patients) were analyzed by the VCS system to demonstrate a characteristic scattergram distribution. Further, we tried to compare scatterplots to the flags of leukemic bone marrow samples and, finally, we compared VCS scatterplots with aberrant antigen expression in AML cases.

RESULTS AND CONCLUSIONS

Overall VCS specificity was 93.1% (54/58) in peripheral blood samples; sensitivity was 100% (42/42) and VCS efficiency was 96%. In AML the characteristic X6 flag was observed in 95.23% of the cases (40/42). In peripheral samples discrimination was made between AML M1 with agranular blasts > 50% of the non erythroid cells (NEC), M4, M5 on the one hand, and AML M1 with granular blasts > 50% of NEC, M2, M3 on the other: the X5 flag was often present in the second group because of the different localization of the cells (p = 0.001). In all normal bone marrow samples we observed granuloblasts in different maturation stages in the neutrophil region of the DF1 VCS scatterplot corresponding to the X5X6 flags or, rarely, to the X5X6X1, because of the presence of immature erythroid cells. This association X5X6 was never observed alone in patients affected by AML. In our study, it was difficult to identify peculiar scatterplots and alarms for each FAB class of AML. Nevertheless, we observed that in all M4 and M5 FAB cases the blastic cells both in the peripheral blood and in the bone marrow samples were located in the monocyte region, with the frequent presence of the X3 flag often associated with the X6 flag. Eight out of the 16 AML bone marrow samples (1 FAB M0, 1 M2, 1 M3, 2 M4, 3 M5) showed the X2 flag and partial localization of blasts in the lymphoid region. In all these cases the presence of some small blastic cells with agranular cytoplasm was confirmed by morphological observation and cytochemical stainings.