If a person is suspected to have ALL due to the presented signs and symptoms, some investigations are required to confirm the diagnosis of the disease. Further, these investigations can help in determining the extent of disease or spread of the disease to different body parts, which in turn help in selecting an appropriate treatment approach. Following are some commonly used diagnostic tools for ALL:
1.Blood Tests: Blood tests provide very important information that provides direction to the diagnostic workup of ALL. Following are the commonly employed blood test for the diagnosis of the ALL:
- Complete Blood Cells Count (CBC): This test provides information on the level of RBCs, WBCs, and platelets. Usually, RBCs and platelets are reduced and WBCs may be reduced or increased.
- Blood Smear: In this test, a drop of a blood sample is spread on a glass slide and this is observed under a microscope. It helps in detecting any change in the appearance and number of various blood cells.
Apart from above blood tests, blood coagulation tests (disseminated intravascular coagulation panel) and some blood chemistry analyses (the level of creatinine, uric acid, potassium, calcium, phosphorus, and lactate dehydrogenase (LDH) level) may also be employed.
2.Bone Marrow Aspiration/Biopsy: Aspiration samples contain a small number of cells and biopsy contains a tiny piece of tissue collected from the bone with the help of a biopsy needle. The biopsy sample is then tested in a laboratory and can provide very useful information about the ALL cells such as the type ALL, the severity of cancerous changes involved, and the presence of specific defective genes or proteins. Following are various techniques used for collecting this information:
- Immunohistochemistry: In this technique, a very thin portion of biopsy sample is first attached to a microscope glass slide. The sample is then treated with a specific antibody which gets attached to a protein specific to certain types of cancer cells. Some reagents are then added to the treated sample that causes the bound antibody to change its color. The change in color of the antibody-protein complex can be observed under the microscope, which confirms the type of cancer cells.
- Flow cytometry: In this technique, the aspiration sample is first treated with some fluorescent antibodies that get attached to certain specific proteins (antigens) on the surface of cells. The treated sample is then analyzed using a laser beam and a detector attached to a computer. This test can detect different types of cells along with the quantification of each type of cells.
- Cytogenetic Testing: In this technique, chromosomes are evaluated for certain defects which are common in ALL. The sample cells are first grown into the culture medium and are observed under a microscope after adding certain reagents that bind only to a specific defective portion of a chromosome. This test enables detection of chromosomal abnormalities like translocation, amplification, or deletion.
- Fluorescent in situ hybridization (FISH): In this technique, a fluorescent RNA probe is used which binds to a specific portion of a chromosome in the sample cells. Then, the sample can be examined under a microscope to determine the presence of certain chromosomal abnormalities like translocation, addition, or deletion. This technique is very sensitive, fast, and accurate. Thus, this technique is preferably used for detecting chromosomal abnormalities.
- Polymerase chain reaction (PCR): This is a very sensitive diagnostic tool which can detect a very small number of leukemia cells with a specific genetic change, for example, Philadelphia chromosome. This technique is generally used to diagnose minimum residual disease (MRD) in patients after treatment.
3.Imaging Tests: Utility of imaging tests is limited for the diagnosis of ALL. However, these tests can be used to detect the involvement of different body parts by leukemia.
- Computed tomography (CT) scan: In this technique, detailed cross-sectional images of body organs are generated using x-rays. It can be utilized for scanning neck, chest, abdomen and pelvis for the diagnosis of any abnormal lymph node or involvement of liver, spleen, or other structures.
- Magnetic resonance imaging (MRI) scan: This technique provides detailed images of internal body structures using radio waves, strong magnetic field, and gadolinium-based contrast material (which is used via intravenous injection to improve the clarity of the MRI images). It can be utilized for scanning neck, chest, abdomen and pelvis for the diagnosis of any abnormal lymph node or involvement of liver, spleen, or other structures. It is considered very sensitive to detect the involvement of CNS the patients with neurological symptoms.
- Lumbar Puncture: In this procedure, a sample of cerebrospinal fluid (CSF, a biological fluid that surrounds the brain and spinal cord) is collected with the help of a needle inserted up to the space around the spinal cord through the lower part (lumbar region) of the spine. The collected sample is then analyzed in a laboratory for the presence of leukemia cells. Generally, >/=5 leukocytes cells/microliters of CSF with the presence of lymphoblasts is considered as the CNS leukemia. This technique can also be used to deliver a treatment to the CSF.
Investigational tests play an important role in assessing the response to treatment, which in turn help in selecting an appropriate second-line of treatment. Following are various terms used to indicate the different responses to treatment:
1.Complete response: A complete response means absence of leukemia cells in the blood and <5% blasts in bone marrow. Any sign or symptom of the disease like spleen/liver enlargement should return to normal.
2.Refractory Disease: When complete response cannot be achieved after induction treatment, the disease is termed as a refractory disease. Second-line of treatment is usually employed in such cases.
3.Disease Relapse: When leukemia cells are detected in blood or any other body part (including CNS) or >5% blasts in bone marrow, after complete remission, it is known as relapsed disease.
4.Minimal Residual Disease (MRD): When leukemia cells are undetectable with conventional diagnostic technique after treatment but detectable with a more sensitive technique such as PCR, or flow cytometry, it is known as MRD. Patients with MRD after treatment are more likely to have disease relapse. Thus, after induction treatment, MRD assessment should be performed to assess the disease prognosis.
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