Diagnosing acute lymphoblastic leukaemia

Your doctor will take a sample of blood and send it to a laboratory for a full blood count (FBC). This will show whether leukaemia cells are present and whether the levels of different types of blood cells are different from what would be expected in a healthy person.

The blood tests will also check for infections such as HIV (human immunodeficiency virus) or hepatitis.

If the blood test shows abnormalities in the number or appearance of the white blood cells, your doctor will want to check a sample of your bone marrow for signs of leukaemia. This is because blood cells develop in your bone marrow. Samples of bone marrow are usually collected from the hipbone (pelvic bone) and there are 2 different ways to collect these samples.

• Bone marrow aspiration – The doctor uses a thin needle to remove a small amount of fluid (aspirate) from the bone marrow.
• Bone marrow biopsy or trephine – The doctor uses a slightly larger needle to remove a small amount of bone and marrow.

You will be given a local anaesthetic to numb the area. To help you relax, you may be offered a light sedation that you inhale (a mild pain reliever known as “the green whistle”) or is injected through a small plastic tube inserted into a vein (cannula).

This may make you feel drowsy, so ask a family member or friend to drive you home afterwards. It can take up to 30 minutes to prepare for a bone marrow test, but the actual procedure takes only a few minutes.

The bone marrow samples are sent to a laboratory. A specialist called a pathologist will do tests on the samples to work out the subtype of ALL.

These tests may include:

Immunophenotyping – This test looks for certain markers that are found on the surface of leukaemia cells. Looking at the patterns of these markers can help your doctor to confirm that the leukaemia is ALL (and not AML) and to work out the subtype and the type of lymphocyte (B-cell or T-cell) affected. B–cell ALL is the most common type of ALL in adults.

Genomic and other tests – Genomic testing looks for gene changes on a particular cell. The results of these tests help doctors diagnose the subtype of ALL, guide treatment, monitor response to therapy and predict if the leukaemia is likely to come back after a
period of remission (relapse).

A genomic test called PCR (polymerase chain reaction) may be used to look for common gene changes in ALL. You might also have a test called FISH (fluorescence in situ hybridisation), which looks for abnormal chromosomes (including the Philadelphia chromosome).

You may have other tests to find out more about the ALL, your general health and how well your organs are working. This may include a chest x-ray, a computerised tomography (CT) scan, ultrasound and a magnetic resonance imaging (MRI) scan.

Other tests may include:

HLA typing – If a stem cell transplant may be an option, a blood or bone marrow sample will be tested for human leukocyte antigen (HLA). HLA is found on most cells in your body – it helps your immune system recognise which cells belong in your body. A stem cell transplant can usually only go ahead if the donor is a close match to your HLA type. This is why your close relatives may also have an HLA test.

Gated heart pool scan – This scan is used to see how well the heart is working and whether you are fit enough for chemotherapy. A small amount of blood is taken, mixed with some radioactive material and injected back into your body. A special camera takes pictures of the blood being pumped by your heart.

Lumbar puncture – Once you have been diagnosed with ALL you will have a lumbar puncture. This test shows if any leukaemia cells have travelled to the fluid around your spine and brain (called cerebrospinal fluid). A sample of cerebrospinal fluid is removed with a thin needle from a space between 2 bones in the lower back. This takes only a few minutes, but it can be uncomfortable, so your doctor will use a local anaesthetic to numb the area. A lumbar puncture may be done under x-ray guidance.

In some people, the back of the legs may tingle when the needle is inserted – this is harmless and doesn’t last long. You may get a headache afterwards but this usually improves within hours.

PET–CT scan – For some types of ALL, you may have a positron emission tomography (PET) scan combined with a CT scan. Before the scan, you will be injected with a small amount of radioactive glucose solution. Leukaemia cells show up brighter on the scan because they take up more of the glucose than normal cells do.

Lymph node biopsy – If your lymph nodes are swollen, you may have a biopsy. Depending on where in the body the swollen nodes are, you may have a local or general anaesthetic. The lymph node/s will be removed through a small cut in the skin and sent to the laboratory for testing.

Most cells in the human body have 23 pairs of chromosomes. Chromosomes are threadlike structures that contain sets of instructions known as genes.

Chromosome 22 is abnormal in about 1 in 4 adults with ALL. This is known as the Philadelphia chromosome.

The Philadelphia chromosome is not inherited and cannot be passed on to your children – it is a gene change that happens to some people during their lifetime. This chromosome contains the BCR-ABL gene (see diagram below).

BCR-ABL is considered a cancer gene because it is present only in developing leukaemia cells. It carries instructions for the body to produce an abnormal type of protein called tyrosine kinase, a protein that tells leukaemia cells to grow and multiply.

Drugs are sometimes used to block tyrosine kinase.

Gene swap

The Philadelphia chromosome is formed when parts of 2 chromosomes break off and switch places. A gene from chromosome 22, called BCR, and a gene from chromosome 9, called ABL, create the BCR-ABL gene.