Acute Lymphocytic Leukemia (ALL) is diagnosed through a series of tests that examine the blood and bone marrow. The process usually begins with a physical examination where the doctor checks for physical signs of ALL such as pale skin, swollen lymph nodes, and enlargement of the liver and spleen. If ALL is suspected, the following tests may be conducted:

Blood Tests:

1. Complete blood count (CBC): A CBC is one of the initial blood tests performed. It provides information about the numbers and types of blood cells in the bloodstream, including:
   • White blood cell count: Elevated white blood cell counts may suggest leukemia
   • Hemoglobin levels: Low hemoglobin levels can indicate anemia
   • Platelet count: Low platelet counts may lead to bleeding problems
2. Peripheral blood smear: A peripheral blood smear is a microscopic examination of a stained blood sample. It allows for the examination of the appearance of blood cells, including their size, shape, and distribution. Abnormal-looking cells, such as lymphoblasts or leukemic cells, may be seen in the blood smear.

Bone Marrow Tests:

1. Bone marrow aspiration and biopsy: This test is usually needed to confirm a diagnosis of ALL. This test involves taking a small amount of bone marrow, usually from the hip bone. The sample is examined under a microscope to determine the percentage of blast cells (immature cells) present in the bone marrow. A high percentage of blast cells is a hallmark of ALL. A diagnosis of ALL generally requires a sample to have greater than 20% bone marrow lymphoblasts. 

2. Flow cytometry immunophenotyping: Flow cytometric immunophenotyping on the bone marrow aspirate sample is performed to identify certain cell surface markers that help determine which type of leukemia a person has. ALL is classified into two immunophenotypic groups: B-cell ALL and T-cell ALL based on the results of this test. The specific markers for B-cell ALL may include CD10, CD19, CD20, and CD22. T-cell ALL may express markers such as CD2, CD3, CD4, CD5, CD7, and CD8.

3. Karyotyping: Utilizing the bone marrow sample, this test looks at the chromosomes found within cells and is able to identify if any chromosomal abnormalities are present. This test is recommended in all suspected cases of ALL. 

4. Fluorescence in situ hybridization (FISH) test: FISH is more sensitive than karyotyping in finding genetic abnormalities and helps identify the most common genetic changes a person with ALL may have. Abnormalities that cannot be detected by karyotyping but can be found by FISH include ETV6-RUNX1 and iAMP21. FISH can detect the presence of the Philadelphia chromosome, which results from a translocation (exchange of genetic material) between chromosomes 9 and 22, leading to the BCR-ABL1 fusion gene. Ph-positive ALL, which occurs in about 25% of people with ALL, is associated with a poorer prognosis but may be able to be treated with specific targeted therapies. FISH can also identify other translocations, such as t(12;21) or TEL-AML1 fusion, which are associated with favorable outcomes in pediatric ALL.

Lumbar Puncture (Spinal Tap):

A lumbar puncture is not typically used as a primary diagnostic test for ALL, but may be performed in certain situations. ALL can sometimes involve the central nervous system, and it's important to assess whether leukemia cells have spread to the brain and spinal cord. A lumbar puncture is used to obtain cerebrospinal fluid (CSF), which surrounds the brain and spinal cord. CSF can be examined for the presence of leukemia cells.

Imaging Tests:

Imaging tests such as X-rays, CT scans, or MRIs are not usually used to directly diagnose ALL itself, but they may be used in certain situations. Imaging tests may be used to detect or monitor complications related to ALL, such as infections, bleeding, or organ enlargement caused by leukemia cells. They may also be used once a diagnosis of ALL is confirmed as part of the staging process to determine the extent of disease involvement and whether it has spread to other parts of the body. This information helps guide treatment decisions.

A Summary of Diagnosing Acute Lymphocytic Leukemia

It's important to note that the diagnosis and classification of ALL is complex and requires a comprehensive evaluation by a team of specialists. A complete diagnosis requires a physical examination, looking at a bone marrow sample under the microscope, immunophenotyping, karyotype analysis and often molecular genetic testing. The specific markers and genetic changes found in the bone marrow sample can also help determine a person's prognosis and guide treatment decisions. If you don't currently have an ALL specialist on your team, it is important that you consult with one. Use HealthTree's ALL Specialist Directory to locate a specialist near you. 

Want to Learn More About Acute Lymphocytic Leukemia?

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