Canterbury DHB

Context

Laboratory Diagnosis

The diagnosis is established by the laboratory investigations outlined below:

Integration of the above findings leads to the precise diagnosis being established. We are currently using the WHO 2016 Classification. When all the laboratory tests have been completed, the laboratory sends out a Summary of Laboratory Findings report.

In This Section

Morphology of Blood and Bone Marrow

Immunophenotyping

Cytogenetics

DNA Analysis

The Decision to Treat

Morphology of Blood and Bone Marrow

The blood changes are quite variable but usually show a normocytic anaemia, neutropenia, and thrombocytopenia. The proportion of blast cells in the blood ranges from barely detectable to 300–400 x109/L. A bone marrow is usually performed in order to establish the diagnosis and to carry out the further tests listed below. If the blast count is very high a bone marrow may not be required. In AML the blast cells are myeloblasts, and in general more than 20% need to be present in the bone marrow to establish a diagnosis of acute leukaemia.

Immunophenotyping

The primitive leukaemic cells carry antigens on their surface/cytoplasm that indicate a myeloid origin in patients with AML. These may be stem cell antigens (CD34), myeloid antigens (CDs 117,13,33), monocytic antigens (CD14). Rarely, erythroid (Glycophorin A) or megakaryocyte (CDs 42b or 61) markers may be present. On occasion, markers ordinarily found on lymphoid cells may be detected (e.g., CD2) and this aberrant phenotype may be useful in residual disease monitoring. Biphenotypic (lymphoid and myeloid) acute leukaemias do occur, but are rare.

For a full account of immunophenotyping in AML, refer to the WHO Classification of Tumours - Pathology and Genetics of Tumours of Haemopoietic and Lymphoid Tissues, 2016.

Minimal residual disease monitoring by flow performed in Auckland is part of the updated (July 2018) version of AML19 (see below).

Cytogenetics

Cytogenetic changes in AML leukaemic cells are common and many of these may have therapeutic or prognostic significance. The AML trials 10 & 12 had defined 3 groups – poor, standard, and good risk based on cytogenetic analysis. These have been further refined for the current AML 19 trial in a risk score that combines the cytogenetics with other factors including response and is calculated after cycle 1, or in the case of NPM1 positive patients, cycle 2.

DNA Analysis

DNA analysis is essential for any patient who will receive intensive treatment and will define what DNA change may underlie the cytogenetic abnormalities observed on karyotype. As part of AML19 these are performed free of charge in the Cardiff lab with the results then entered on to Éclair. The two most important molecular changes are FLT3 and NPM1.

The Decision to Treat

About this Canterbury DHB document (4274):

Document Owner:

Ruth Spearing (see Who's Who)

Issue Date:

October 2018

Next Review:

October 2020

Keywords:

Note: Only the electronic version is controlled. Once printed, this is no longer a controlled document. Disclaimer

Topic Code: 4274