Acute Myelogenous Leukemia (AML) Workup

Updated: Sep 16, 2017
  • Author: Karen Seiter, MD; Chief Editor: Emmanuel C Besa, MD  more...
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Workup

Approach Considerations

The workup for acute myelogenous leukemia (AML) includes the following:

  • Blood tests
  • Bone marrow aspiration and biopsy (the definitive diagnostic tests)
  • Analysis of genetic abnormalities
  • Diagnostic imaging

Immunophenotyping by flow cytometry of bone marrow or peripheral blood samples can be used to help distinguish AML from acute lymphocytic leukemia (ALL) and further classify the subtype of AML. Cytogenetic studies performed on bone marrow provide important prognostic information and can guide treatment by confirming a diagnosis of acute promyelocytic leukemia (APL).

Perform human leukocyte antigen (HLA) or DNA typing in patients who are potential candidates for allogeneic transplantation.

In patients with signs or symptoms suggesting central nervous system (CNS) involvement, computed tomography (CT) or magnetic resonance imaging (MRI) should be performed. Lumbar puncture is indicated in those patients if no CNS mass or lesion is detected on CT or MRI. [21]

Chest radiographs help assess for pneumonia and signs of cardiac disease in individuals with AML.

Evaluation of myocardial function is needed once the diagnosis of AML is confirmed because many of the chemotherapeutic agents used in treatment are cardiotoxic. Echocardiography or multiple gated acquisition (MUGA) scanning is particularly important for patients who have a history or symptoms of heart disease or risk factors for iatrogenic cardiotoxicity (ie, exposure to cardiotoxic drugs or thoracic radiotherapy). [21] All patients should have a baseline electrocardiogram before starting treatment for AML.

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Blood Studies

Complete blood count

A complete blood count (CBC) with differential demonstrates anemia and thrombocytopenia to varying degrees. Patients with AML can have high, normal, or low white blood cell (WBC) counts.

Coagulation studies

The most common abnormality is disseminated intravascular coagulation (DIC), which results in an elevated prothrombin time, a decreasing fibrinogen level, and the presence of fibrin split products. Acute promyelocytic leukemia (APL), also known as M3, is the most common subtype of AML associated with DIC. Patients with acute monocytic leukemia also have a high incidence of clinically significant DIC.

Peripheral blood smear

Review of the peripheral blood smear confirms the findings from the CBC count. Circulating blasts are usually seen. Schistocytes are occasionally seen if DIC is present.

Blood chemistry profile

Most patients with AML have an elevated lactate dehydrogenase (LDH) level and, frequently, an elevated uric acid level. Liver function tests and blood urea nitrogen (BUN)/creatinine tests are necessary before the initiation of therapy. Elevation of those test results, in a patient with an elevated WBC (>25 × 109/L), indicate possible tumor lysis syndrome, and treatment should be started immediately.

Blood culture

Appropriate cultures should be obtained in patients with fever, or with signs of infection even in the absence of fever.

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Flow Cytometry (Immunophenotyping)

Flow cytometry (immunophenotyping) can be used to help distinguish AML from acute lymphocytic leukemia (ALL) and further classify the subtype of AML (see the table below). The immunophenotype correlates with prognosis in some instances.

Table 1. Immunophenotyping of AML Cells (Open Table in a new window)

Marker Lineage
CD13 Myeloid
CD33 Myeloid
CD34 Early precursor
HLA-DR Positive in most AML, negative in APL
CD11b Mature monocytes
CD14 Monocytes
CD41 Platelet glycoprotein IIb/IIIa complex
CD42a Platelet glycoprotein IX
CD42b Platelet glycoprotein Ib
CD61 Platelet glycoprotein IIIa
Glycophorin A Erythroid
TdT Usually indicates acute lymphocytic leukemia, however, may be positive in M0 or M1
CD11c Myeloid
CD117 (c-kit) Myeloid/stem cell
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Cytogenetic Analysis

Cytogenetic studies performed on bone marrow provide important prognostic information (see the tables below). They are useful for confirming a diagnosis of APL, which bears the t(15;17) chromosome abnormality and is treated differently.

Table 2. Common Cytogenetic Abnormalities in AML (Open Table in a new window)

Abnormality Genes Involved Morphology Response
t(8;21)(q22;q22) AML/ETO M2 Good
inv(16)(p13;q22) CBFb/MYH11 M4eo Good
Normal Multiple Varies Intermediate
-7 Multiple Varies Poor
-5 Multiple Varies Poor
+8 Multiple Varies Intermediate-poor
11q23 MLL Varies Intermediate-poor
Miscellaneous Multiple Varies Intermediate-poor
Multiple complex* Multiple Varies Poor
* Refers to 3-5 different cytogenetic abnormalities, depending on the classification used.

Table 3. Cytogenetic Abnormalities in APL (Open Table in a new window)

Translocation Genes Involved All-Trans-Retinoic Acid Response
t(15;17)(q21;q11) PML/RARa Yes
t(11;17)(q23;q11) PLZF/RARa No
t(11;17)(q13;q11) NuMA/RARa Yes
t(5;17)(q31;q11) NPM/RARa Yes
t(17;17) stat5b/RARa Unknown

Fluorescence in situ hybridization (FISH) studies can be used to get a faster overview of cytogenetic abnormalities than traditional cytogenetic studies. FISH does not replace cytogenetics.

Although it has been known for some time that patients with multiple cytogenetic abnormalities have a poor prognosis, Breems et al demonstrated that a monosomal karyotype (defined as two or more distinct autosomal monosomies or one single autosomal monosomy in the presence of structural abnormalities) confers a particularly poor prognosis. [22] Several other groups have since confirmed this finding. [23, 24]

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Molecular Marrow Evaluation

Several molecular abnormalities that are not detected with routine cytogenetics have been shown to have prognostic importance in patients with AML. The bone marrow should be evaluated at least with the commercially available tests. Patients with APL should have their marrow evaluated for the PML/RARa genetic rearrangement. When possible, the bone marrow should be evaluated for Fms-like tyrosine kinase 3 (FLT3) and nucleophosmin (NPM1) mutations.

FLT3 is the most commonly mutated gene in persons with AML and is constitutively activated in one third of AML cases. [25] Internal tandem duplications (ITDs) in the juxtamembrane domain of FLT3 exist in 25% of AML cases. In other cases, mutations exist in the activation loop of FLT3. Most studies demonstrate that patients with AML and FLT3 ITDs have a poor prognosis. Analysis of FLT3 is commercially available.

Mutations in NPM1 are associated with increased response to chemotherapy in patients with a normal karyotype. [26] Thiede et al studied FLT3 and NPM1 in 1485 patients with AML. [27] The analysis of the clinical impact in 4 groups (NPM1 and FLT3 -ITD single mutants, double mutants, and wild-type [wt] for both) revealed that patients having only an NPM1 mutation (without a FLT3 -ITD) had a significantly better overall and disease-free survival and a lower cumulative incidence of relapse. [27] Analysis of NPM1 is commercially available.

Mutations in CEBPA are detected in 15% of patients with normal cytogenetics findings and are associated with a longer remission duration and longer overall survival. [28] ERG overexpression is an adverse predictor in cytogenetically normal AML.

A study by the Cancer and Leukemia Group B (CALGB) found that high BAALC expression was associated with FLT3-ITD, wild-type NPM1, mutated CEBPA, MLL-PTD, absent FLT3-TKD and high ERG expression. In a multivariate analysis, high BAALC expression independently predicted lower complete remission rates when ERG expression and age were adjusted for and shorter survival when FLT3-ITD, NPM1, CEBPA and WBC count were adjusted for. [29]

The clinical impact of MLL partial tandem duplication (MLL-PTD) was evaluated in 238 adults aged 18 to 59 years with cytogenetically normal de novo acute myeloid leukemia who were treated by CALGB. Of the patients with MLL-PTD, 92% achieved complete remission compared with 83% of patients without MLL-PTD.

Ley et al identified a somatic mutation in DNMT3A, encoding a DNA methyltransferase, in the cells of a patient with AML and a normal karyotype. [30] The authors sequenced the exons of DNMT3A in 280 additional patients with de novo AML to define recurring mutations. A total of 62 of 281 patients (22.1%) had mutations in DNMT3A that were predicted to affect translation. These mutations were highly enriched in the group of patients with an intermediate-risk cytogenetic profile but were absent in all 79 patients with a favorable-risk cytogenetic profile. The median OS among patients with DNMT3A mutations was significantly shorter than that among patients without such mutations (12.3 mo vs. 41.1 mo, P < 0.001).

Schwind et al measured miR-181a expression in pretreatment marrows in 187 adults (< 60 y) with CN-AML. Higher miR-181a expression was associated with a higher complete remission (CR) rate (P =.04), longer OS (P =.01) and a trend for longer disease-free survival (P =.09). The impact of miR-181a was most striking in poor molecular risk patients with FLT3-internal tandem duplication (FLT3-ITD) and/or NPM1 wild-type, where higher miR-181a expression associated with a higher CR rate (P =.009) and longer disease-free survival (P < .001) and OS (P < .001). In multivariable analyses, higher miR-181a expression was significantly associated with better outcome, both in the whole patient cohort and in patients with FLT3-ITD and/or NPM1 wild-type. These results were also validated in an independent set of older (≥60 y) patients with CN-AML. [31]

Gene-expression profiling is a research tool that allows a comprehensive classification of acute myelogenous leukemia (AML) based on the expression pattern of thousands of genes. [32] Marcucci used next-generation sequencing analysis of methylated DNA to identify differentially methylated regions associated with prognosis in older patients with AML. Seven genes were associated with prognosis (CD34, RHOC, SCRN1, F2RL1, FAM92A1, MIR155HG, and VWA8). The fewer the genes with high expression, the better the prognosis. [33]

Several groups have demonstrated that mutations in IDH1 and IDH2 have an adverse effects on prognosis in AML. Next-generation sequencing can detect these abnormalities and can identify patients who are candidates for therapies targeting these mutations. [34]

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Other Tests

Chest radiographs help assess for pneumonia and signs of cardiac disease in individuals with AML.

Multiple gated acquisition (MUGA) scanning is needed once the diagnosis of AML is confirmed because many chemotherapeutic agents used in treatment are cardiotoxic.

Electrocardiography should be performed before treatment of AML.

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Histologic Findings

The traditional FAB classification of AML is as follows:

  • M0 - Undifferentiated leukemia
  • M1 - Myeloblastic without differentiation
  • M2 - Myeloblastic with differentiation
  • M3 - Promyelocytic
  • M4 – Myelomonocytic; M4eo - Myelomonocytic with eosinophilia
  • M5 - Monoblastic leukemia; M5a - Monoblastic without differentiation; M5b - Monocytic with differentiation
  • M6 - Erythroleukemia
  • M7 - Megakaryoblastic leukemia

The newer WHO classification is as follows [1] :

  • AML with recurrent genetic abnormalities - AML with t(8;21)(q22;q22), (AML1/ETO); AML with abnormal bone marrow eosinophils and inv(16)(p13q22) or t(16;16)(p13)(q22), (CBFB/MYH11); APL with t(15;17)(q22;q12), (PML/RARa) and variants; AML with 11q23 (MLL) abnormalities
  • AML with multilineage dysplasia - Following myelodysplastic syndrome (MDS) or MDS/myeloproliferative disease (MPD); without antecedent MDS or MDS/MPD but with dysplasia in at least 50% of cells in 2 or more lineages
  • AML and MDS, therapy related - Alkylating agent or radiation-related type; topoisomerase II inhibitor type; others
  • AML, not otherwise classified - AML, minimally differentiated; AML, without maturation; AML, with maturation; acute myelomonocytic leukemia; acute monoblastic or monocytic leukemia; acute erythroid leukemia; acute megakaryoblastic leukemia; acute basophilic leukemia; acute panmyelosis and myelofibrosis; myeloid sarcoma

See also Acute Myeloid Leukemia Staging.

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