Comparison of flow cytometry and enzyme cytochemistry for the detection of myeloperoxydase in acute myeloid leukaemia: interests of a new positivity threshold

Abstract

Following the recommendations of the European Group for the Immunological Characterization of Leukaemias (EGIL) in 1995, few reports have been published comparing enzyme cytochemistry (EC) and flow cytometry (FC) for the detection of myeloperoxydase (MPO) in acute myeloid leukaemia (AML). The EGIL guidelines defined MPO positivity in FC, by the presence of this enzyme in 10% or more of the blast cells. We studied 136 adult patients with the systematic use of both EC and FC, using a 3% threshold for positivity for EC, and 10% and 3% consecutively for FC. FC was less sensitive than EC using the currently recommended threshold of 10%, but a 3% cut-off showed more sensitivity and was superior to EC. The joint use of both techniques identified 14 discordant patients (positive in FC/negative in EC or vice versa), all of whom displayed at least one poor-prognosis biological factor, which correlated with a mediocre clinical result. In conclusion, we recommend that the cut-off for a positive MPO value should be lowered to 3%, and suggest that the concomitant use of FC and EC is a fast clinically relevant prognostic tool.

Flow cytometry thresholds of myeloperoxidase detection to discriminate between acute lymphoblastic or myeloblastic leukaemia

“…Data obtained from ROC curves for the three thresholds for isotype control and residual lymphocytes used as reference are presented. * (Bene et al , ); **(Peffault de Latour et al , ).…”

“…The cytochemistry 3% threshold proposed by Peffault de Latour et al (2003) yielded an excellent sensitivity of 100%, but an unacceptably low specificity (68Á7% and 21Á1% for the isotype control or lymphocytes). This low threshold might therefore wrongly lead to a conclusion of mixed-phenotype acute leukaemia (MPAL) diagnosis according to the WHO classification (Borowitz et al, 2008), in clinical practice ( Fig 1E).…”

Identification of acute myeloid leukemia in dogs using flow cytometry with myeloperoxidase, MAC387, and a canine neutrophil‐specific antibody

“…Leukemia is defined as being of myeloid (ie, granulocytic or monocytic) lineage when ≥3% of blasts are positive for MPO by use of enzyme cytochemistry; the cut‐off value for flow cytometry is less well defined. The European Group for Immunological Characterisation of Leukaemia recommends a cut‐off value of 10% in human leukemias,20 but a more recent study recommended using a 3% cut‐off value 25. Discordant results between the 2 techniques may be obtained (positive by cytochemistry, but negative by flow cytometry, or vice versa), but are less likely when the lower threshold is used.…”

“…Discordant results between the 2 techniques may be obtained (positive by cytochemistry, but negative by flow cytometry, or vice versa), but are less likely when the lower threshold is used. Discordant results may be associated with poor prognosis 25. Flow cytometry is more sensitive than cytochemistry in detecting the presence of MPO when the lower threshold is used.…”

Acute Leukemias of Ambiguous Origin

“…35,36 A threshold of 10% expression has been used by the EGIL group. 3 However, discordant cases are found when both methods are compared, 6,37 leading to the conclusion that the 10% threshold may be conservative but not very sensitive. It should be emphasized that MPO expression can be a difficult test to establish by FCM immunophenotypic analysis since differences in permeabilization reagents and various antibodies have been reported.…”