What laboratory tests or procedures can help rule out leukemia, specifically acute monocytic (Acute Monocytic Leukemia) or acute myelomonocytic (Acute Myelomonocytic Leukemia) leukemia?

From the Guidelines

To rule out acute monocytic or myelomonocytic leukemia, a comprehensive diagnostic work-up including a complete blood count (CBC) with differential, bone marrow aspiration and biopsy, flow cytometry, cytogenetic analysis, and molecular testing is essential. This approach is supported by the American Society of Clinical Oncology (ASCO) clinical practice guideline endorsement of the College of American Pathologists and American Society of Hematology guideline, as outlined in the Journal of Clinical Oncology 1.

Initial Diagnostic Steps

• A complete blood count (CBC) with differential is the first step to identify abnormal cell counts and the presence of immature cells in peripheral blood.
• Bone marrow aspiration and biopsy are definitive tests that examine the production of blood cells and can detect leukemic cells, as recommended by the guideline 1.
• Flow cytometry is crucial for identifying specific cell markers characteristic of these leukemia types, particularly monocytic markers like CD14, CD64, and CD11b.

Additional Testing

• Cytogenetic analysis and molecular testing should be performed to detect genetic abnormalities associated with these leukemias, such as MLL gene rearrangements or mutations in genes like NPM1 and FLT3, as stated in the guideline 1.
• Lumbar puncture may be considered to check for central nervous system involvement, with flow cytometry analysis of cerebrospinal fluid (CSF) recommended for patients with suspected or confirmed acute leukemia 1.
• A comprehensive metabolic panel is necessary to assess organ function and monitor for potential tumor lysis syndrome.

Importance of Comprehensive Testing

The tests collectively provide a comprehensive evaluation that can effectively rule out or confirm acute monocytic or myelomonocytic leukemia, allowing for prompt treatment if needed. Early diagnosis is critical as these acute leukemias can progress rapidly and require immediate intervention. Furthermore, ensuring that flow cytometry analysis or molecular characterization is comprehensive enough to allow subsequent detection of minimal residual disease (MRD) is a strong recommendation 1.

Key Recommendations

• Bone marrow aspiration and biopsy are essential for the diagnosis of acute leukemia.
• Flow cytometry and cytogenetic analysis are critical for identifying specific cell markers and genetic abnormalities.
• Molecular testing should be performed to detect genetic abnormalities associated with these leukemias.
• Comprehensive metabolic panel and lumbar puncture may be necessary for a thorough evaluation.

From the Research

Labs and Testing Procedures to Rule Out Leukemia

To rule out leukemia, especially acute monocytic or myelomonocytic leukemia, several labs and testing procedures can be employed:

• Bone marrow biopsy and aspiration to examine the bone marrow cells and identify any abnormalities 2
• Cytomorphological examination to identify the type of leukemia cells present 2, 3
• Cytochemical tests, such as nonspecific esterase, to confirm the diagnosis of monocytic or myelomonocytic leukemia 2
• Immunophenotyping by multiparameter flow-cytometry (MFC) to identify the specific antigens expressed on the surface of the leukemia cells 3
• Complete blood count (CBC) to evaluate the number of white blood cells, red blood cells, and platelets in the blood
• Blood smear examination to identify any abnormal cells in the blood

Specific Markers for Acute Monocytic and Myelomonocytic Leukemia

Certain markers can help distinguish between acute monocytic and myelomonocytic leukemia:

• CD56 coexpression is commonly found in acute monoblastic/monocytic leukemia (AMoL) 3
• CD2 coexpression is more commonly found in chronic myelomonocytic leukemia (CMML) 3
• Lack of CD13 and HLA-DR expression can also be seen in CMML 3

Treatment and Prognosis

The treatment and prognosis of acute monocytic and myelomonocytic leukemia can vary:

• Venetoclax-based treatment has shown poor outcomes in patients with monocytic subtypes of acute myeloid leukemia (AML) 4
• 5-Azacytidine has been shown to be effective in treating acute myeloblastic leukemia 5
• The prognosis of patients with monocytic subtypes of AML is generally poorer than those with non-monocytic subtypes 4