Acute Myeloid Leukemia Diagnosis

The first clue to a diagnosis of AML is typically an abnormal result on a complete blood count. While an excess of abnormal white blood cells (leukocytosis) is a common finding, AML can present with isolated decreases in platelets, red blood cells, or even with a low white blood cell count (leukopenia).

A bone marrow examination is often performed to identify the type of abnormal blood cells; however, if there are many leukemic cells circulating in the peripheral blood, a bone marrow biopsy may not be necessary. Marrow or blood is examined via light microscopy as well as flow cytometry to diagnose the presence of leukemia, to differentiate AML from other types of leukemia (e.g. acute lymphoblastic leukemia), and to classify the disease according to the above systems. A sample of marrow or blood is typically also tested for chromosomal translocations by routine cytogenetics or fluorescent in situ hybridization.

The diagnosis and classification of AML can be challenging, and should be performed by a qualified hematopathologist or hematologist. In straightforward cases, the presence of certain morphologic features (such as Auer rods) or specific flow cytometry results can distinguish AML from other leukemias; however, in the absence of such features, diagnosis may be more difficult.

The diagnosis of AML is established by demonstrating involvement of more than 20% of the blood and/or bone marrow by leukemic myeloblasts, according to the WHO criteria.^[1] AML must be carefully differentiated from "pre-leukemic" conditions such as myelodysplastic or myeloproliferative syndromes, which are treated differently.

Because acute promyelocytic leukemia (APL) has the highest curability and requires a unique form of treatment, it is important to quickly establish or exclude the diagnosis of this subtype of leukemia. Since APL is always characterized by a specific chromosomal translocation (t15;17), this is most often done by FISH performed on blood or bone marrow, which can quickly demonstrate the presence or absence of the 15;17 translocation.

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