If acute lymphocytic leukemia (ALL) is suspected, a physician will take the child’s medical history and perform a complete physical examination. During the physical examination, the physician may inspect the lymph nodes, spleen and liver for swelling.

Next, a variety of tests may be ordered to diagnose and classify the leukemia. Samples of cells from the child’s blood and bone marrow will be examined by a pathologist to verify the diagnosis. Tests will be conducted to determine if the ALL has spread to the central nervous system (brain and spinal cord) or to other areas of the body. Additional tissue and cell samples may be needed to guide treatment.

Common tests include:

• Complete blood count and blood smear. A complete blood count (CBC) is a blood test that measures the number of red blood cells, white blood cells and platelets in a sample of blood. The test also measures the amount of hemoglobin in the red blood cells as well as other factors.  Changes in the numbers of different blood cell types and the appearance of the cells can suggest leukemia. Children with ALL usually have too many white blood cells and many of the cells will be lymphoblasts, an early form of lymphocyte. Many children with ALL also have too few red blood cells and platelets.
  
  
• Blood chemistry tests. These tests measure the level of specific chemicals in the blood. They are used to monitor changes in liver or kidney function caused by leukemia or treatment with certain chemotherapy drugs. The tests may also be ordered to determine whether treatment is required to correct abnormally low or high levels of certain minerals or to detect infection in the child’s bloodstream.
  
  
• Bone marrow tests. A bone marrow aspiration involves using a thin needle to collect a small sample of liquid bone marrow. A bone marrow biopsy uses a larger needle to remove a piece of bone marrow. Usually performed at the same time, these procedures may be ordered to determine if leukemia is present or to monitor treatment.
  
  
• Lumbar puncture. Also known as a spinal tap, this procedure uses a needle to remove a sample of cerebrospinal fluid (CSF) from between the bones in the lower spine. The sample is then examined for leukemia cells. The test may also be ordered to deliver chemotherapy drugs into the spinal fluid when leukemia cells are found there.
  
  
• Testicular biopsy. This procedure involves removing a sample of tissue or cells from the child’s testicles. The sample is then examined under a microscope for signs of cancer.

Additional tests include laboratory tests to diagnose and classify the leukemia. These include:

• Cytochemistry. This test involves placing cells on glass microscope slides and exposing them to chemical stains. The stains then react with certain types of leukemia cells and change color. The test may be ordered to distinguish one form of leukemia from another.
  
  
• Flow cytometry. This procedure uses fluorescent antibodies to detect certain molecules on the surface of leukemia cells. This test may be ordered to determine the exact type of leukemia or to distinguish leukemia from other diseases. It is also used to determine the amount of DNA in the cancer cells, an important factor in determining the child’s prognosis (outlook).
  
  
• Cytogenetics. This test uses a microscope to evaluate the characteristics of cells including their formation, function and structure. It may be ordered to determine if the cells have too many chromosomes, or if the chromosomes have any translocations (the transfer of DNA from one chromosome to another). Identifying translocations helps to distinguish certain types of ALL and is important in determining the child’s prognosis.
  
  
• Immunocytochemistry (immunotherapy).This procedure uses special antibodies to detect certain molecules on the surface of leukemia cells. The cells being examined are treated with the antibodies, which attach themselves to certain types of molecules. The cells containing these molecules then change color. The cells are then examined under a microscope. This test may be ordered to determine the exact type of leukemia or to distinguish leukemia from other diseases. 
  
  
• Molecular genetic studies. These tests examine leukemia cell DNA. They may be ordered to detect translocations that are too small to detect under a microscope with cytogenic tests. Molecular genetic studies are useful in classifying ALL because many of its subtypes have distinctive translocations. Information about the translocations can also be used to predict the child’s response to treatment. After treatment, the tests may be ordered to detect leukemia cells that can be missed under a microscope. 

ALL rarely forms visible tumors. For that reason, imaging tests have limited value. If imaging tests are done on patients with ALL, they are usually being conducted to diagnose infections or related problems rather than the leukemia. Imaging tests that may be ordered include:

• Chest x-ray. This test uses low doses of radiation to produce images of the chest on film paper or fluorescent screens. It can reveal signs of a lung infection and detect enlargement of the thymus or lymph nodes in the chest.
  
  
• Computed tomography (CT) scan. Also known as a computed axial tomography (CAT) scan, this test allows for multiple x-rays to be taken from different angles around the child. It also may be performed with a contrast medium (dye) to define the structures in the body more clearly. CT scanning is helpful in detecting an accumulation of leukemia cells as well as enlarged lymph nodes or organs.

• Magnetic resonance imaging (MRI). This test uses a powerful magnetic field to create images of structures and organs within the body allowing a computer to produce very clear cross-sectional or three-dimensional images. It may be ordered to determine if the disease has spread to the spinal cord or brain. As with CT scans, a contrast medium may be injected into the patient to help define structures.
  
  
• Gallium scan and bone scan. In these procedures, a child receives an injection of a radioactive substance that is often absorbed by areas of the body where ALL is present or bone is damaged. The tests may be ordered when a child has bone pain that may be due to ALL or an infection.
  
  
• Ultrasound. This procedure uses high-frequency sound waves to produce images of internal organs. The ultrasound machine emits high-frequency sound waves, which reflect off the area of the body being examined. The reflected waves are picked up by a computer that translates the information into an image. This test is useful for detecting an enlarged kidney, liver or spleen.