Methods to assess measurable (formerly minimal) residual disease (MRD) in acute myeloid leukaemia (AML) are playing an increasing role in everyday clinical practice. Multi-parameter flow cytometry (MFC) and molecular analyses have been shown to have powerful prognostic significance and are instrumental in risk directed management.
MRD is a formidable area of flow cytometry and while there is no international standardisation, the European LeukemiaNet (ELN) MRD Working party has published a consensus document to help clarify scientific issues in the measurement and application of MRD in AML.
The recommended ELN MFC approach is the “LAIP-based DfN” (leukaemia associated immunophenotype based, difference from normal approach). The plasticity of AML phenotypes is well recognised, and this approach allows detection of emerging new aberrancies and can be used in the absence of a diagnostic baseline with the MRD panel.
Establishing stringent testing conditions in the laboratory to support this approach is challenging.
In 2017 our laboratory set up the UK MRC AML19 MRD panel to enable NZ patients to be enrolled in the trial, and MRD data to be supplied back to the Reference laboratory. This entailed implementing strict control of reagents and testing conditions, stringent monitoring of flow cytometers, and consensus in the gating strategy and interpretation, in line with the Reference laboratory.
We have found this process time consuming, and requiring considerable input by all involved, but it is essential to ensure provision of quality data to the clinicians in a timely manner.