Your child will have a set of tests to confirm whether they have ALL or not. At any time, you can ask your healthcare team to tell you why your child is having a certain test and what the results mean.
Tests to diagnose ALL
The most important tests to find out if your child has ALL are the full blood count and bone marrow aspirate.
Full blood count
A full blood count (FBC) measures the number of each type of cell in the blood: red cells, white cells and platelets. It also allows your child’s doctors to look for leukaemia cells in the blood.
Your child will have this test quite often throughout their treatment and you may wish to keep track of the results of their blood counts. If you choose to do this, your child’s consultant or specialist nurse will be able to explain what the results mean.
Bone marrow aspirate (biopsy)
Your child’s doctor will take a bone marrow sample to see how the blood is working inside your child’s bone marrow. Your child will have this test a number of times throughout their treatment.
A small amount of bone marrow is taken from the pelvic bone using a needle (an aspirate). Your child’s doctors will then look at the bone marrow sample under a microscope to assess for any disease which may be in it.
Your child will have their first bone marrow test when they’re in hospital at the time of their diagnosis. However, almost all of your child’s bone marrow tests after this can be done as an outpatient (meaning they won’t need to stay in hospital overnight). The procedure is usually quick but it can be uncomfortable for the short time that the sample is being taken from the marrow. For this reason, the doctors will usually give your child a general anaesthetic so they’ll sleep through the procedure.
Bone marrow trephine (biopsy)
At the same time as the bone marrow aspirate is done, your child’s doctor will also do a trephine biopsy. This is the removal of a core of bone marrow from the pelvic bone under the same anaesthetic. This sample provides information about the structure of the bone marrow and the number and distribution of the different blood cell types and cancer cells if present.
Tests after diagnosis
If your child is diagnosed with ALL, the doctors will carry out a number of further tests. These will give them more information about the disease and help them decide how much treatment your child needs in order to have the best possible chance of being cured, with the least possible side effects.
Leukaemia cells can sometimes get into the fluid that surrounds the brain and spinal cord (known as cerebrospinal fluid or CSF). A lumbar puncture involves taking a small sample of CSF to check if there are any leukaemia cells in it. Your child’s doctor will very carefully insert a needle between the bones of the lower spine into the space around the spinal cord and remove a few drops of CSF.
Your child will have a number of lumbar punctures throughout their treatment – not only at diagnosis stage. The doctors will give chemotherapy into the CSF at the same time as these lumbar punctures. This is in order to treat any leukaemia cells that may be present in the CSF, and to prevent the leukaemia from spreading to the CSF.
A lumbar puncture is usually done under general anaesthetic, just like the bone marrow test. For older children, the doctors may offer a sedative instead.
All kinds of cancer, including blood cancer, involve changes in genes in the affected cells. The study of these changes is called cytogenetics or molecular genetics. These gene changes aren’t the same thing as a faulty gene that you inherit from a family member which causes cancer.
Your child’s doctors will carry out cytogenetic tests on cells from your child’s blood or bone marrow samples to find out information about the exact changes present in the cells.
The results of cytogenetic tests are particularly important in helping the doctors decide how much treatment your child needs, and whether your child’s condition is likely to respond to standard treatment.
Minimal residual disease (MRD) test
Minimal residual disease (MRD) refers to the small number of leukaemia cells that are still present in the bone marrow, even if your child is responding well to treatment. It’s normal for there to be some MRD after the early stages of treatment and it doesn’t mean that your child can’t be cured with further treatment.
When your doctors look at blood cells through a microscope, the lowest number of leukaemia cells they can detect is about one leukaemia cell in 20 normal cells. The MRD test is much more sensitive and can detect leukaemia cells at levels as low as one leukaemia cell in 100,000 normal cells.
The results of the MRD test will help your doctors decide how much treatment your child needs.