Diagnosis

Laboratory tests provide the basis for diagnosing ALL.

Flow Cytometry

Flow cytometry uses light to count blood cells in a stream of fluid. It is an important tool used to diagnose leukemia, determine its progress, and tell if any disease remains after treatment. It can also determine the components and structural features of individual cells. Flow cytometry can process thousands of cells in seconds.

Complete Blood Cell Count

A complete blood cell count (CBC) is the first step in diagnosing ALL. However, blood tests do not always detect leukemia. About 10% of patients with ALL have a normal blood cell count. A CBC may show various findings, including:

• The presence of circulatory leukemic blast cells (may miss the cells on occasion) 
• The presence and severity of anemia
• The count of a variety of blood cell types (a high white blood cell count indicates a more severe disease)

Click the icon to see an illustrated series detailing a complete blood cell count test.

Bone Marrow Biopsy

If blood test results are abnormal or the doctor suspects leukemia despite normal cell counts, a bone marrow aspiration and biopsy are the next steps. These are very common and safe procedures. However, because this test can produce considerable anxiety, particularly in children, parents may want to ask the doctor if sedation is appropriate for their child.

• A local anesthetic is given.
• A needle is inserted into the bone, usually the rear hipbone. There may be brief pressure or pain. A small amount of marrow is withdrawn. Marrow looks like blood.
• A larger needle is then inserted into the same place and pushed down to the bone. The health professional will wiggle the needle from side to side to loosen a larger specimen for the biopsy. The patient will feel some pressure.
• The sample is then taken to the lab to be analyzed. All the results are completed within a couple of days.

Click the icon to see an image of bone marrow removal.

Normal bone marrow contains 5% or less blast cells (the immature cells that ordinarily develop into healthy blood cells). In leukemia, abnormal blasts constitute between 30 - 100% of the marrow.

Spinal Tap

If bone marrow examination confirms ALL, a spinal tap may be performed, which uses a needle inserted in to the spinal canal. The patient feels some pressure and usually must lie flat for about an hour afterward to prevent severe headache. This can be difficult, particularly for children, so parents should plan reading or other quit activities that will divert the child during that time. Parents should also be certain that the professional administering this test is highly experienced.

Click the icon to see an image of a spinal tap.

A sample of cerebrospinal fluid with leukemia cells is a sign that the disease has spread to the central nervous system. In most cases of childhood ALL, leukemia cells are not found in the cerebrospinal fluid.

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Review Date: 12/17/2005
Reviewed By: Harvey Simon, MD, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital