METHODS: EMA detection was performed by flow cytometry in monocytes and monoblasts. EMA expression was compared with other known markers of monocytic-macrophage lineage (CD11c, CD14 and intracellular CD68). Samples of purified monocytes were obtained from 20 healthy volunteers. Twenty-two cases of monocytic AML (M4 and M5) were studied and controls were selected from 20 cases of acute lymphoblastic leukaemia (ALL) and 18 cases of non-monocytic AML (M0, M1, M2, M3, and M7).
RESULTS: EMA was shown to be expressed strongly on the surface of all purified monocytes. EMA expression was observed on blast cells in 18/22 (81.8%) cases of AML M4 and M5, but not in that of non-monocytic AML or ALL. In this study EMA monoclonal antibody has demonstrated a strong association (P<0.001) with all the other known markers of monocytic-macrophage lineage in acute leukaemia subtypes. EMA had also shown 100% specificity and 81.8% sensitivity in the diagnosis of AML M4 and M5.
CONCLUSIONS: The monoclonal antibody EMA (clone E29) is a useful marker in the classification of acute myeloid leukaemia and can be used as a supplementary analysis for the diagnosis of acute leukemia with monocytic involvement.