From the Guidelines
The most definitive test for diagnosing Acute Lymphoblastic Leukemia (ALL) is a bone marrow aspiration and biopsy with subsequent immunophenotyping, cytogenetic analysis, and molecular studies, as recommended by the NCCN Guidelines for Pediatric Acute Lymphoblastic Leukemia, version 2.2025 1.
Diagnosis of ALL
The diagnosis of ALL requires a comprehensive approach, including:
- Morphologic examination of malignant lymphocytes using Wright-Giemsa–stained slides and hematoxylin and eosin–stained core biopsy and clot sections
- Comprehensive immunophenotyping with flow cytometry and/or immunohistochemistry
- Baseline characterization of leukemic clone(s) by flow cytometry or molecular assay (eg, immunoglobulin [Ig] or T-cell receptor [TCR] gene rearrangements) to facilitate subsequent analysis of minimal residual disease (MRD)
Importance of Bone Marrow Examination
The bone marrow examination is essential for diagnosing ALL, as it provides comprehensive information about the leukemic cells' characteristics, which directly influences treatment protocols and helps predict outcomes for patients with ALL. While peripheral blood smears and complete blood counts may suggest ALL, they are not definitive.
Role of Immunophenotyping
Immunophenotyping using flow cytometry identifies specific cell surface markers that distinguish ALL from other leukemias and classifies it as either B-cell or T-cell lineage. This information is crucial for guiding treatment decisions and predicting outcomes.
Cytogenetic and Molecular Analysis
Cytogenetic analysis and molecular studies detect chromosomal abnormalities and genetic mutations that provide prognostic information and guide treatment decisions. These tests are essential for identifying specific subtypes of ALL and determining the best course of treatment.
Recent Guidelines
The NCCN Guidelines for Pediatric Acute Lymphoblastic Leukemia, version 2.2025, recommend a comprehensive diagnostic workup, including bone marrow aspiration and biopsy, immunophenotyping, cytogenetic analysis, and molecular studies 1. These guidelines emphasize the importance of a thorough diagnostic evaluation to ensure accurate diagnosis and optimal treatment of ALL.
From the Research
Diagnostic Tests for Acute Lymphoblastic Leukemia (ALL)
- The most definitive test for diagnosing ALL involves a combination of morphological, cytochemical, and immunological analyses, as well as cytogenetic studies 2, 3, 4, 5, 6.
- Cytogenetic analysis, including karyotyping and fluorescence in situ hybridization (FISH), is crucial for identifying specific genetic abnormalities associated with ALL, such as t(9;22) and t(1;19) 2.
- Bone marrow biopsy and aspiration are essential for diagnosing ALL, as they provide information on the morphology, cytochemistry, and immunophenotype of the leukemic cells 3, 4, 5, 6.
- Peripheral blood blasts can also be used for diagnosis, especially when the blast count is 30% or more, but bone marrow samples are often necessary for cytogenetic analysis and to confirm the diagnosis 4, 5.
- The French-American-British (FAB) classification system is used to categorize ALL into different subtypes (L1, L2, and L3) based on morphological and cytochemical features 6.
Comparison of Diagnostic Tests
- Plasma viscosity (A) is not a specific test for diagnosing ALL.
- Full blood count (B) can provide initial clues, such as an elevated white blood cell count, but is not definitive for diagnosing ALL.
- Peripheral blood film (C) can show blast cells, but a bone marrow biopsy and cytogenetic analysis are necessary to confirm the diagnosis.
- Cytogenetics (D) is the most relevant test among the options, as it can identify specific genetic abnormalities associated with ALL.