Assessment of monocytic component in acute myelomonocytic and monocytic/monoblastic leukemias by a chemiluminescent assay

Introduction: Classically, the monocytic component of acute myelomonocytic (FAB-M4) and acute monocytic/monoblastic (FAB-M5) leukemias is demonstrated by nonspecific esterase positivity in cytochemical stainings. We have previously demonstrated that nonspecific esterases from normal monocytes can be determined by a chemiluminescent method. In the present study, we investigated whether this assay can also determine the monocytic component of FAB-M4 and FAB-M5 and distinguish these acute myeloid leukemia (AML) categories. Materials and Methods: Bone marrow samples were obtained from 66 patients with AML (M0, two cases; M1, 12 cases; M2, 13 cases; M3, 10 cases; M4, 11 cases; M5, 12 cases; M6, two cases; M7, four cases). Cells were incubated with a standard reaction mixture and chemiluminescence was measured for 10min. Two parameters were assessed, the peak (PLE) and the integrated light emission (ILE). Results: Both PLE and ILE were higher in FAB-M4 and FAB-M5 subtypes compared to other AML subtypes (P < 0.001). In addition, the classification of AML cases into FAB-M4, FAB-M5 and nonmonocytic subtypes based on ILE analysis was concordant with α-naphthyl acetate esterase (ANAE) in 97% of cases (kappa coefficient 0.94, P < 0.001). Conclusions: These findings indicate that this chemiluminescent assay was able to determine the monocytic component of FAB-M4 and FAB-M5 cells, and the classification of AML subtypes based on chemiluminescent analysis strongly agreed with the cytochemical ANAE-staining. In conclusion, this chemiluminescent assay is a simple, fast and objective method, which may be useful as an alternative tool in the differential diagnosis of AML subtypes.